Category: hydroponic agriculture

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The low sensitivities and relatively low R2 values are less than those found in sand or clay soils

While circle-packing nearly describes our model problem, there is one major caveat: no physical justification prevents the circles from overlapping one another. This ’soft boundary’ makes it possible to achieve 100% coverage of the domain by allowing overlap. If the only objective was to maximize the effective areal coverage of the field, then one could distribute sensors next to one another without discretion. However, the monetary cost of sensors, sensor operation, and sensor maintenance makes this approach unreasonable, which motivates our stated objective of maximizing field coverage with the fewest number of sensors possible.The outcome of this algorithm is that sensors are placed throughout the field such that sensors are placed in the largest gaps between sensors. This is done by incrementing the acceptable distance between sensors by a small amount and then making many attempts at placing a sensor before repeating the process. We score the fitness of each placement design by the ratio of the number of field pixels that are within the half-variogram range of a sensor to the total number of pixels in the field. In other words, what percentage of the field area is within the half-variogram range of one or more sensors? This process is repeated until it is impossible to place a sensor outside of the range of all other sensors in the design, or until the field is completely covered. The flowchart for this algorithm is shown in Figure 5.3A, and a schematic depicting the evolution of sensor placement in an arbitrary field shape is shown in Figure 5.3B.Soil is a complex environment. It is a three-phase medium containing organic matter, minerals, metals, ceramics, gases, water, and a host of biological life. This is all to say that many things could complicate potentiometric nitrate sensor readings. Although the nitrate sensor nodes are sensitive to nitrate and are largely insensitive to most other ions – soil is more complicated than aqueous solutions. Ideally, nitrate sensors should not be sensitive to soil properties ,plastic garden pot but calibration or direct measurement of the interfering property could help return accurate nitrate measurement values.

To characterize the performance of the nitrate sensor nodes in soil, the potential of the nodes was recorded over time in varying nitrate concentrations and moisture levels in three types of agricultural soils. After calibrating the nitrate sensor nodes in aqueous solutions, they were immediately cycled through several containers of soil saturated with aqueous solutions of varying nitrate concentrations. Finally, they were measured in several containers of dry soil with varying volumes of 10 mM nitrate solution. The nitrate sensor nodes were tested in sand, peat, and clay soils. Sand tests were performed with commercially available desert sand , consisting of only sand-sized soil particles and no initial nitrate concentration. Clay tests were performed with an agricultural clay soil utilized for perennial alfalfa and from Bouldin Island in the Sacramento–San Joaquin Delta, California . Peat tests were performed in Miracle-Gro Nature’s Care organic potting mix. To circumvent the possibility of hysteresis attributed to the exposure of one soil type before measuring the sensor node in another soil type, the sensors were only measured in a single kind of soil on a given day, and the stakes were gently but thoroughly cleaned with deionized water and dried between measurements. In the nitrate concentration experiment, aqueous solutions of 0.1 mM – 1 M NaNO3 were used to saturate an array of containers containing sand, clay, or peat soils, depending on which soil type the sensors were being tested in that day. After saturating the soil with a surplus of nitrate solution, the sensor nodes were placed in the 0.1 mM container by displacing the soil with a spoon, inserting the stake, and then gently redistributing the soil over the electrode surfaces. After the nitrate sensor node was inserted into the container, the program ran on the micro-controller, uploading the recorded potential over WiFi to an online spreadsheet once per minute. Once the potential of the sensor stabilized, it was then moved to the 1 mM container, and so on. Figure 5.11 shows the nitrate sensor nodes being measured in the sand. After the measurements were made, the nitrate concentration of the soils was determined by taking KCl extractions and then measuring the extractions with ionexchange chromatography. The nitrate sensor nodes’ responses to the calibrated nitrate concentrations are plotted in Figure 5.12.

We expect similar results in measuring the sensor nodes in saturated sand as we would in aqueous solutions. This is because sand has a low cation exchange capacity, so few other ionic species are present. Furthermore, uncharged solids in the soil are unlikely to interfere with the potentiometric measurement.The nitrate sensor nodes in the sand showed strong linear relationships between nitrate concentration and recorded potential, with about half of the 17 sensor nodes included in this trial showing R2 values above 0.99. Eight sensor nodes with R2 > 0.99 were used for the remaining analysis. The average sensitivity for these sensors was -42 ± 8 mV/dec. Figure 5.12A shows the linear relationship between nitrate concentration and output potential for five of the sensors in the sand, with sensitivities ranging from -40 to -42 mV/dec. In clay, five of 14 sensors had R2 values > 0.9, and the sensitivity of the sensor nodes was -39 ± 8 mV/dec mV/dec, shown in Figure 5.12C. Clay has a much finer grain size and higher cation exchange capacity than sand. This likely explains the loss in sensitivity when measuring in clay compared to an aqueous solution or saturated sand. This suggests that soil texture alone is not a primary interfering factor in soil nitrate measurements, though other soil characteristics may be. If this is the case, calibration of the sensor in different soil types would be necessary to deploy such devices in agricultural applications. Figure 5.12B shows the output potential of three nitrate sensor nodes in peat soil at varying nitrate levels. The nitrate sensor nodes demonstrated sensitivities of -31 ± 8 mV/dec,draining pots with R2 values for each sensor’s best fit line of 0.8, 0.71, and 0.99.We suspect this is because the sensors had become damaged by the time of these measurements. The sensors were measured in sand and clay soils before the measurements in peat, so by the time of these measurements, the sensors had been inserted, removed, and rinsed from soil media many times, and it is possible that despite our best efforts, the sensing element may have become damaged. Compared to Figure 4.10, which plots ‘fresh’ gold electrode nitrate sensors in the same soil type measured with a Campbell Scientific data logger, the sensitivity was -47 mV/dec, R 2=0.95, and E0 variation 30 mV . The different results depending on the age of the sensor and the electronics used to measure it highlights the importance of improved stability for real-world use cases.

To find the impact of moisture content on the sensor nodes, 10 mM nitrate solution was used to water an array of containers containing sand, clay, or peat soils, depending on which soil type the sensors were being tested in that day. The containers were watered to 0 – 50% volumetric water content in 10% increments. The sensor nodes were initially placed in 0% VWC soil while the program ran on the micro-controller, uploading the recorded potential over WiFi to an online spreadsheet once per minute. Once the potential of the sensor node stabilized, it was then moved to the 10% VWC container, and so on. Ideally, the sensors’ output signal should not depend on soil moisture content. However, potentiometric sensors require ionic contact between the two electrodes to function: ions must be able to move freely between the ISE and RE, proportional to the finite current associated with potentiometric measurements. If soil does not hold enough water to support the flow of ions, the sensor becomes an open circuit, and there would be no signal. The results are shown in Figure 5.13. The potential abruptly increases at low moisture content because the micro-controller is programmed to report high signal output at open-circuit inputs. However, above a certain moisture threshold, sand and clay soils follow the expected pattern: relatively constant potential with respect to moisture content. For sand, the threshold is between 10 and 20% volumetric water content VWC, while for clay, it is between 20 and 30%. This makes sense because clay’s matrix potential is higher than sand’s, meaning water is bound more tightly to the surfaces of solid particles in clay, lowering the likelihood of an ionic pathway forming between the ISE and the RE of the nitrate sensor. The relationship between water content and sensor signal output in peat soil is less clear. The minimum water threshold seems to be between 10-20%, but the output potential is not as stable between 30-50% VWC. This could be attributed to the possibility of damage buildup in the nitrate sensors, or it could indicate that different sensors have different minimum thresholds. It could also be explained by the variations of water retention in high-organic matter soil. Further investigation is warranted.As noted earlier, there is significant E0 variability from one sensor node to another. Up until now, the behavior of the nitrate sensor nodes has been plotted altogether. However, when we look at individual sensors, E0 is relatively consistent, indicating that the variability has to do mainly with the sensor nodes rather than the properties of the soil. Individual sensor nodes have relatively consistent E0 values across the different trials. Subsets of the same 20 sensors were used in the six plots shown in Figures 5.12 and 5.13. The sensors with low R2 in the sand also had low R2 in clay, while most sensors with high R2 in the sand also had high R2 in clay . Similarly, sensors with relatively high potential outputs had this characteristic across soil types and nitrate/moisture measurements. Figure 5.14 shows the response of two sensor nodes measured in sand and clay soils. Sensor A has a much lower potential than Sensor B in all cases. A common misconception surrounding ‘green materials’ is that if something will decompose or degrade into a naturally-occurring material , it is safe to deploy into the environment. This is an incomplete way of thinking because, by that definition, every material on the planet is ‘green.’ Stop reading for a moment and take a look around you. Everything you see would eventually break down into naturally-occurring materials on a long enough time scale devoid of human intervention. It was made of materials sourced from our planet, after all. The time it takes for something to degrade is also essential and is the basis of many different standards surrounding bio-degradation. Different organizations worldwide have developed standards that benchmark different degrees of how things degrade. Table 5.2 highlights some of the more widely known standards. Interestingly, these standards vary widely in the description, and only the compostability standards explicitly state the timescale at which those materials degrade. The standards in Table 5.2 also lack to describe of how these materials might degrade. To design devices that degrade in a controlled manner, one must first understand the different ways a material might degrade. There are three ways in which materials degrade. These are compositional or micro-structural changes, time-dependent deformation and associated damage accumulation, and environmental attack. Generally, materials degrade by some combination of several mechanisms. There are few opportunities for time-dependent deformation in soil, though several mechanisms catalyze compositional changes or attack material bonds. These primary mechanisms by which materials degrade in soil are discussed here. For most materials, microbial activity is the primary contributor to the degradation rate. Microbial and enzymatic digestion describes the degradation carried out by microorganisms and naturally-occurring enzymes. Microbes can degrade most – if not all – naturally occurring organic chemicals and convert them to inorganic end products to supply the microbes with nutrients and energy. As with other life forms, the material’s molecular bonds are broken to release energy, transformed into a less thermodynamically energetic material, and excreted from the microbe’s system. Intuitively, different materials degrade at different rates. Generally, more complex molecular structures degrade on longer time scales than simpler ones. Also, different microbes and enzymes are preferential to different molecular compounds.

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New methods for evaluating uncertainty also can be used to devise model simplification strategies

A holistic upscaling from the point source to the landscape scale requires incorporation of several interacting, complex components, adding substantial complexity above and beyond the agricultural system itself. Thus, a major consideration in environmental modeling is how to best capture essential interactions while maintaining models that are feasible to implement with available data and computational resources. Fig. 4 illustrates the various components linking point to landscape scales. A first element for the linkage from point to landscape is estimation of surface and subsurface fluxes and ecological transitions along the lateral scale. Coupling with landscape microclimate models provides the vertical inputs used by the agricultural systems models, as well as gradients along the landscape. Coupling with hydrological models provides water flow paths like surface runoff, vertical and lateral groundwater flow, and interactions between vadose and groundwater zones and with adjacent surface water bodies . Water quality models provides sediment and solute transport along the landscape controlled by water flows , and other effects like wind erosion. Integration and upscaling of landscapes into the watershed scale requires 3-dimensional coupling of the surface and subsurface water, energy and mass transfers. At this scale, the groundwater aquifer system typically transcends the boundaries of the watershed and necessitates analysis at the regional scale to evaluate not only the impacts of the cropping and animal production systems on water quantity and quality, but also feed backs from the hydrological system in the agricultural system . Further, mesoscale rainfall and evapotranspiration distribution models control the local surface and subsurface flow intensities,hydroponic pots pollution and abatement. At this scale, human effects through land-use changes as well as ecological dynamics and transitions on natural or protected lands are also an important and critical component to evaluate the overall sustainability of the agricultural system.

Current crop modeling upscaling approaches based on land use maps can be considered an efficient first-order approximation of the environmental linkages. For example, in the USA the US Geological Survey hierarchical system of Hydrologic Units Codes  is commonly used as the reference spatial mapping system to link spatially-explicit hydrological and crop yield simulations. Srinivasan et al. applied the Soil and Water Assessment Tool model to 8-digit subbasin HUCs in the Upper Mississippi River Basin and compared yields of the main crops with observed county-level USDA National Agricultural Statistical Survey data obtained for 1991–2001. SWAT uses spatially distributed watershed inputs to simulate hydrology, sediment and contaminant transport and cycling in soils and streams, and crop/vegetative uptake, growth and yields. Because many counties in the NASS database have missing data it was necessary to aggregate the crop yield data and simulation results to 4-digit sub-region HUCs . In general SWAT predicted crop yields satisfactorily over the long-term average for most 4-digit HUC , although errors greater than 20% were found for 14% of the HUCs studied. Further information on crop management may improve SWAT’s perform conclude that these errors stem likely from those predicting AET and soil moisture storage at these large aggregated scale, and “one could extend the validity and confidence in the model prediction of AET and soil moisture using a well-compared model on crop yield” . Thus, next generation models should consider the lateral connections through the landscape and regional scales to evaluate the sustainability of the integrated system, including effects on water and soil resources quality and quantity and ecological value. Although model complexity has increased in recent years and is a natural outcome of the proposed next generation integrated modeling, there has been little work to rigorously characterize the threshold of relevance in integrated and complex models. Formally assessing the relevance of the model in the face of increasing complexity would be valuable because there is growing unease among developers and users of complex models about the cumulative effects of various sources of uncertainty on model outputs .

New approaches have been proposed recently to evaluate the uncertainty-complexity relevance modeling trilemma , or to identify which parts of a model are redundant in particular simulations . Innovative approaches to simplify model outcomes to make them relevant in decision-making will be central to the next generation modeling efforts. For example, the identification of processes that do not influence particular scenarios, and the use of meta models, could allow simplification without affecting results .This thesis is divided into two sections. In the first section, a technical primer is given to provide a starting point for readers interested in sensor, printing, and machine learning technologies. In the second section, these three technologies are combined to demonstrate my dissertation work in developing nitrogen sensor nodes for precision farming applications. Grain growers apply on the order of a hundred to a few hundred pounds of nitrogen per acre, depending on the crop and field conditions. At a cost of tens of cents to a dollar per pound, with prices rapidly increasing in recent months, it is the second highest cost for many crops, outdone only by seeds. Nitrate fertilizer is conventionally applied uniformly across a field despite studies that have shown existing nitrate concentration in the soil can vary significantly on the order of tens of meters. Precision agriculture practitioners aim to designate site-specific management zones to direct more efficient nitrogen application, but the tools they have to gather data are limited. Optical remote sensing can be used to estimate nitrogen in growing plant material, but to get measurements of nitrate in the soil, a soil sample must be collected and taken back to a laboratory, for analysis via chromatography or spectrographic methods. Such measurements are highly accurate, but they are also expensive, labor-intensive, and give data for only one point in time and space. Nitrate is highly mobile, so concentrations change over time. Models can be developed to estimate nitrate fluxes based on measurements at the beginning and end of a season, but these rely on many estimations and assumptions. Environmental quality monitoring and precision agriculture require nitrate sensors that are robust enough to survive field deployment and soil insertion, can be mass-produced, and involve few or no moving parts. Additionally, the data must be simple to read. Printed solid-state potentiometric ion-selective electrode sensors have the potential to meet these criteria. The use of printing methods for sensor fabrication offers several advantages such as low cost, high throughput, and ease of fabrication.

In order to realize the benefits of printing and enable large-scale sensor deployment, both electrodes must be printed.Previous works have shown printed nitrate ISEs for use in aqueous environments and agriculture. Dam et al.demonstrated potentiometric nitrate sensors having a screen-printed nitrate ISE paired with a commercial RE for agriculture applications. Similarly, inkjet-printed nitrate ISEs were reported by Jiang et al. using a commercial Ag/AgCl reference electrode during measurements. In this work, we demonstrate fully printed, potentiometric nitrate sensors and characterized their sensitivity, selectivity, and stability. We then integrated the sensors into a wireless sensor node and characterized its sensitivity to nitrate concentration and moisture levels in the soil. We then replaced the components of the nitrate sensor node with naturally degradable components and characterized the devices. We propose a model-driven paradigm of measuring these sensors using swarms of UAV drones whose flight paths are optimized using machine learning. Finally, we demonstrate the need for sensor arrays to account for the interference that different analytes could cause,grow pot and provide preliminary results for a nitrogen sensor array that measures nitrate, nitrite, and ammonium concentration in aqueous solutions.A sensor is a device that is able to detect and measure some physical quantity of interest and communicate that information to another device or person. A common example of a sensor that you might recognize is the liquid-in-glass thermometer, shown in Figure 1.1. In this type of thermometer, a thin glass tube is filled with a small volume of liquid mercury that collects in a bulb at the bottom. Then, as temperature changes, the mercury expands or contracts in response, causing the peak of the mercury to move up or down the long stem. The stem, as you may know, is calibrated and marked with numbers corresponding to the temperature in Fahrenheit, Celsius, or both. In this example, the sensor detects the change in temperature by the liquid expanding or contracting in the glass tube. The temperature is measured and communicated to a person by the numbered ticks on the thermometer stem. A sensor should not be mistaken for a detector, which is able to detect and communicate a physical quantity, but fails to measure it. Consider for example a smoke detector, such as the one shown in Figure 1.1B. A smoke detector is able to detect whether or not there is smoke, but it doesn’t measure how much smoke there is. To a smoke detector, there is no distinction between a blazing house fire and overcooked salmon: both cause it to brazenly communicate its detection of smoke.Contrary to the thermometer example above, most modern sensors are electronic devices, which will be the type of sensor that will be discussed in this dissertation.

Many electronic sensors work by having some material that is sensitive to the physical quantity that is being measured, causing a property of that material to change with respect to the physical quantity. Other electronic sensors take advantage of natural laws, such as conductive metal wires arranged in a loop to measure the strength of the magnetic field that it’s in. Later in Section 1.2, we will go over the various types of sensors and the transduction mechanisms that a sensor might use. However, regardless of the mechanism or the physical property that is being measured, all electronic sensors have a sensing element that converts the signal of the physical quantity to an electric signal. As a quick aside, the opposite of a sensor is an actuator, which converts an electric signal into a mechanical action. Some common examples of actuators are electrical motors, hydraulic pumps, or pneumatic valves. Sensors and actuators are both transducers, which is a device that converts energy from one form to another. The distinction here is the intended purpose of the device: sensors measure and detect, while actuators perform an action. A more quantitative way of thinking of this is to look at energy conversion efficiency. The efficiency of energy conversion for sensors is immaterial because their purpose is to detect and measure. For example, if one sensor is 10% efficient at energy conversion but is less accurate than a second sensor that is only 2% efficient, then the second sensor is still an objectively better sensor of the two sensors because it is better at detecting and measuring. Contrarily, efficiency is an important metric for actuators because their purpose is to perform an action. An electric motor with a 2W load is objectively better than a motor with a 5W load, assuming they perform the same task equally well. The organization and classification of sensors vary throughout the academic literature and commercial marketplace. This is because there really is no perfect form of organization, as there are many ‘one-off’ devices that sense for some unique purpose or by some unique method. Further, there are many ways to categorize sensors: sensor specifications, sensor materials, transduction mechanisms, the quantity being measured, the field of application, whether the sensor is active or passive, direct or complex, and many, many more. It is analogous to classifying humans: humans can be classified by their age, gender, race, nationality, preferred sports team, favorite color, or the size of their ears. Similarly, sensors can be classified in many such ways.Sensors can also be classified as passive or active types. The distinction is simple: active sensors provide their own energy source to operate, while passive sensors use naturally available energy. An interesting example of both an active and a passive sensor is a camera. In a brightly lit location, natural light will illuminate the photographed subjects and then reflect toward the camera lens, where the camera simply records the radiation provided . In a dark room, however, there won’t be enough ambient light for the camera to record the subjects adequately. Instead, the camera uses its own energy source – the ‘flash’ – to illuminate the subjects and record the radiation reflected off them .

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Public investments in infrastructure support major drivers important to industry success

We have observed the gradual weakening of the position of grower cooperatives and have noted in our stylized history that several have disappeared while others have had to deal with declining market share and financial challenges. Some aspects of mandated marketing programs have been problematic. Some programs have been terminated by grower referendums and others have suffered adverse court decisions in regard to quantity control prorate programs or assessment of the benefits of generic advertising to individual private label firms. The weakened competitive position of grower cooperatives and problematic features of mandated marketing orders are a consequence of the existence of large producers and integrated grower-processors of sufficient size to have market power of their own. This is now more common than it was in the 1920s and 1930s when enabling legislation was initially crafted. We believe that erosion in the contribution of co-ops and marketing orders will likely carry forward into the 21st Century.Population numbers and per-capita incomes are the dominant determinants of ultimate demand for the produce of California farms and ranches. Table 14 reviews California, national, and worldwide prospects for population and economic growth. Demand within the state grew over the epochs with significant increases in population and per-capita incomes occurring in the recent past. The relative growth in California demands will likely exceed that of nationwide per-capita demands in the future, the result of continued immigration and rising incomes. Export demands, important in the early history of the state, have again become important, responding to rising incomes in important offshore markets in Europe, Asia, and elsewhere. It is obvious that California agriculture, being demand driven, must be sensitive to changes that effect state, national, and international demands for the products of its farms and ranches. Issues will relate not only to quantities in trade channels but also to quality and supply reliability. Future marketing opportunities will be defined in importance by trade to both local and distant markets as well as the location of competitive battles for market shares. High export dependency for many of its products, increased in-state population’s demand for food products,pot raspberries slower growth in national markets, and, above all, the possibility of both growing populations and incomes in developing economies will be important determinants for success.

These two drivers reflect the most negative of our outlooks.The SWP, which was funded differently than the CVP , may provide a financial model for future endeavors to serve particular sectors of the state, including agricultural, urban, and environmental water users. Highways are in a deteriorating state. Increased maintenance and traffic congestion add to transportation costs. Local roads are affected by inadequate local funding. Airports and harbors also face difficulties, including the need for health and security assurances. “User pay” may also be the coming mantra for covering the costs of research, development, and extension services. Private agricultural R&D investments now exceed public expenditures, a trend that is sure to continue, possibly to the detriment of discovery of basic scientific research necessary for applied research products. It may also skew products toward large-market products, curtailing development of applied research products focused on smaller markets, e.g., for smaller-volume horticultural crops of the sort common to California. We have postulated that superior management will continue to be a hallmark of a viable agricultural sector in the future. Higher tuition costs reduce public contributions to each student’s education at the state’s colleges and universities. Here, too, the shift ap-pears to be one of user pay, perhaps reducing educational opportunities and, along with that, less public support of the tenet that the benefits of a well-educated population serve society and the general welfare of the citizenry. Extension and public-education programs are also under budget scrutiny with the almost inevitable consequence of reduction if not elimination. Private extension and public-education programs may be developed for those willing to bear the cost. Programs without a core, definable economic market may cease to exist.The increasing regulation of agriculture is driven by environmental, worker, and consumer safety issues, among others. There has been a continuous increase in regulations, compliance challenges , and the like. The majority of regulatory pressures have been imposed since WWII during a period marked by rapid increases in the number of people living in California and a growing slate of concerns by the general public about the environment, labor, health, and consumer policies. A recent study of farmer responses to the effects of regulations reflects one attempt to categorize the broadening scope of regulatory activity: employee-related regulations—safety and health, employee rights, disclosure, transportation; community-related regulations—consumer health and safety, community public health and safety; natural resource-related regulations—air quality, water quality, water rights, threatened or endangered plants or animals, and wetlands; and regulations related to transportation of materials—transportation of hazardous wastes and of goods and materials .

Regulations had a perceived effect on management practices, including those of employee safety and training, paperwork, technology, management support and improvement, cultural practices, scale of operations, and efficiency . We in no way argue that regulatory activities are not in the public interest, but they do increasingly change the policy and regulatory environment within which economic activity exists, constraining options, increasing costs, and reducing the competitiveness of California agriculture. We can admit only to viewing the future as one in which regulations will have profound impacts on firm and industry productivity and competitive performance.The second set of new drivers is the flip side to the positive impact of population and income growth on demand: namely, competition for natural resources. Urban growth has already pushed agriculture virtually out of Los Angeles, Orange, San Diego, San Mateo, and Santa Clara Counties and is now spilling over the Tehachapis from the south and the Coast Range from the west into the Central Valley. Thirty-five million people demand more recreation space, more water, more land, and more public space . When we recognize that only a small part of California is hospitable to human habitation, which, in general, occurs in the same areas where agriculture thrives, the potential for increasing abrasion on the urban-rural interface is inevitable. In summary, both drivers are responsive to the demands of a growing non-farm population in the United States and in California. Both are external forces to which accommodation must inevitably be made. Litigation is only infrequently successful in preventing negative impacts. Agriculture has come to learn to work with other interest groups to make the best of possible outcomes. To the extent that they limit choices of producers and processors, they can add to the cost of production, reducing economic profitability and placing California producers at a competitive disadvantage to producers in other states and even in other countries that are not similarly affected. U.S. markets for some crops may not be affected unless there are alternate producers of the same or substitute products in other states or if there are offshore producers with lower costs of production. Shares of market in third-country markets may be affected if there are global competitors in those same markets with lesser constraints or non-regulated production options.Willard Cochrane in his history of U.S. agriculture argues that agriculture in the United States has basically been “supply driven.” That is, production was initiated for self-consumption , but marketable surpluses emerged as productivity increased.

Contrary to Malthus’ prediction that demand would outrun supply, agriculture in developed countries has been characterized by production expanding more rapidly than demand , leading to oversupply, low prices, and, ultimately,plastic gardening pots government intervention to support incomes. The individual farmer’s main defense to such situations was to improve efficiency by adopting new technology. But if new technology was rational for one, it was rational for all, so aggregate supply expanded further, thus pressing prices to lower levels. The argument thus arises that agriculture is on a perpetual “treadmill” of overproduction and low prices . But California agriculture was not settled by small homesteaders intent on feeding themselves first and then possibly producing small surpluses of basic commodities—grain, milk, eggs, and meat. California agriculture started with big farms and ranches producing much more than could be consumed by the farmers directly. California farmers produced to meet someone else’s demand—for hides and tallow on the East Coast and in Europe, meat for miners and those supplying miners, wheat for export, nuts and dried fruits for the East and Europe, and so on. This dominant focus on meeting changing product demands, coupled with the range of total products possible, meant that California agriculture could be opportunistic. But to be so, it had to constantly adapt to survive and, yes, thrive. Constantly adjusting to changing opportunities has meant that California agriculture has a perpetual thirst for new technology—better and cheaper is always a potential market advantage. Being a long distance from markets for both outputs and inputs placed an extra premium on efficiency and adaptiveness. This set of factors pulled California agriculture through a quick sequence of changes that, as incomes climbed and population grew, meant that California agriculture became more and more diversified—200 crops in 1970, 350 in 2000. A lesser focus on basic crops meant that California agriculture has been less influenced by, or dependent upon, U.S. farm programs. However, if programs offered opportunities, California agriculture made the best of them. After all, an agriculture that is more efficient or productive than that of the rest of the country should be able to perform better. California agriculture has done so in cotton, rice, and dairy. Being less focused on Washington, California agriculture sought favorable state policies on water, transportation, research, and development, as well as favorable tax treatment. Until 1961, rural areas dominated the state senate. California agriculture was able basically to get its own way pre-WWII and remained a powerful force thereafter, at least until it lost the Peripheral Canal battles in the 1970s.

A few other distinctions will round out our case that California agriculture is different. It has always been a capital-intensive but simultaneously very seasonally labor intensive agriculture. California agriculture has always had a strong dependence on distant markets but, as its own state market grew, it adjusted to meet growing “instate” demands. It has benefited greatly from being in the middle of a rapidly growing and rich “domestic” market. Having access to 35 million local customers is preferable to having only 0.75 million or even three million . The constant adjusting to meet changing demands of affluent consumers has had consequences for the nature of California agriculture. Since 1952, the share of output accounted for by annual field crops has fallen precipitously while production of higher-valued vegetable and perennial crops has increased substantially. Dairy production now dominates the livestock sector. The result is that a rising share of California agriculture is on longer, multiyear production cycles. This necessitates a longer planning framework if periodic price run-ups are not to be followed by rapid buildups in production capacity, which inevitably result in market gluts and falling prices. This is currently happening in the wine industry worldwide.It is now time to end this story. We have consulted history. We have argued that California agriculture has performed well compared to U.S. agriculture. Based on the total value of crops and livestock marketed, California became the highest-ranking agricultural state in 1948. It has maintained that ranking ever since while increasing the difference between it and the second most important agricultural state . In 1950 California accounted for 8 percent of the total value of U.S. agricultural production. Since then, the share has steadily risen. In 2000 California agricultural production was worth $25.5 billion, amounting to 13 percent of the U.S. total. The value of California agricultural production of crop and animal products is now more than the combined value of the next two states, Texas and Iowa. But California agriculture’s dependence on federal government farm payments has been significantly less than that of the rest of U.S. agriculture . In 2000 California’s payments amounted to $667 million out of total U.S. direct government payments of $22.9 billion—only about 3 percent of the total. In contrast, Iowa received about 10 percent of U.S. payments and Texas received about 7 percent. It is likely that payments to California producers will fall relative to grain-belt areas because field-crop production will continue to decline as growers shift to higher-gross-income crops as markets permit.

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Producers observed an increasing concentration of off farm processors and marketers

This epoch witnessed an eroding shift from a heavy reliance on production of undifferentiated commodities toward a more diverse, more specialized agriculture that responded more directly to consumer demands for food, fiber, and horticultural products. Beginning with an expanding production base in the San Joaquin Valley that was initially heavily devoted to field-crop production, California agriculture aggressively shifted over time toward higher-valued, more capital-intensive crops as markets permitted. The mass of production for many products shifted into the San Joaquin Valley from both the south and the north as markets expanded. Producers throughout the state scrambled to find opportunities that yielded acceptable economic returns to factors of production. The large shares marketed through cooperatives declined as producers apparently lost confidence that co-ops could make the transition to consumer-demand-driven marketing as efficiently as newer players focusing on more diversified market outlets for their products. Contractual arrangements and supply coordination increasingly replaced open or spot markets even for undifferentiated commodities.Some producers invested heavily to better integrate their operations vertically and horizontally to achieve economies of size and scope. The introduction to the state’s agricultural statistical summary for 1970 noted that “some 200 crops are grown in California, including seeds, flowers, and ornamentals” . The statistical report for the 2000 crop year reported a significant numerical revision, noting that “some 350 crops are grown in California,big plastic pots including seeds, flowers, and ornamentals” , nearly doubling crop numbers over the three decades.

The crops currently on the market reflect a much wider array of processed forms to better satisfy consumer and food-service institution demands. The increased number of commodities and product forms available reflected changes in the composition of both domestic and export demand. Domestic population increased substantially. Higher income, dual-income households demanded new product forms, and the growth of ethnic populations brought new crop demands, particularly from growing numbers of Hispanic and Asian consumers. Many consumers preferred and demanded convenience over even the most basic food preparation for many of their meals. Per-capita consumption shifts included changes in livestock demands and in the demand for more fresh, rather than processed, forms of many vegetables and fruits. Export markets also required different product forms than did domestic markets. By the end of the 20th Century, there were nearly 35 million people residing in California . One out of eight persons in the United States now resided in California, making the state’s diverse population an important, primary market for food and nursery products. The epoch began and ended with two contrasting water-resource scenarios that were also greatly influenced by population growth. Agriculture, which foresaw prospective ample quantities in the 1970s, now, in the face of resource competition from urban and environmental demands, was confronted with increasing water-resource scarcity and uncertainty at the turn of the century. Increased surface-water deliveries occurred following completion of Oroville Dam and San Luis Reservoir in 1967 and 1968, respectively, and with extensions of the California Aqueduct serving west-side and southern San Joaquin agriculture in the early 1970s. The Kern County Intertie Canal, which connected the east side of the valley with the aqueduct, was completed in 1977, signaling the state’s completion of major surface-water delivery systems. Even though there was a pronounced shift from field crops to higher-valued commodities in major areas of the San Joaquin Valley, the large increment in newly developed, better-irrigated lands served a total of 4.25 million acres of major field crops in 1970—a level even higher than that reported for 1950.

Later in the epoch, extensive crop acreage fell with the addition of more higher-valued crops. A second significant increment in surface-water availability was extension of the CVP’s Tehama-Colusa Canal, enabling intensification of production on the west side of the Sacramento Valley . Thus, California agriculture was flush with new surface-water supplies at the outset of this epoch. However, two of the century’s more severe droughts occurred during this period—the first in 1976–77 and the second over the period 1987–1992. The former was more severe, but the latter, longer drought had a far greater impact on agriculture. Both droughts sharply reduced water deliveries from the north to meet the growing needs of San Joaquin Valley agriculture. Average runoff in the Sacramento and San Joaquin hydrological areas fell to half of normal levels in the 1987–1992 drought. As a consequence, groundwater extractions in the San Joaquin Valley exceeded recharge by 11 million acre-feet during the 1987–1992 drought . At the end of the epoch, agricultural water supplies were reduced by new CVPIA requirements on CVP deliveries plus an inability to transfer supplies through the Delta due to environmental and physical system concerns even if surface water was available. The imminent reduction of Colorado River water supplies to the Metropolitan Water District of Los Angeles could also reduce surplus water supplies and create additional competition for moveable water. Water markets were developed during this period to facilitate the transfer of water among individuals and agencies in both annual and longer-term arrangements. But surplus water to serve future agricultural uses had evaporated from the system. Astute water management, including water transfers and water banking, was required in most agricultural regions by the end of the epoch.The early 1970s can be characterized as a period of aggressive expansion fueled by improving world markets and concern about “feeding a hungry world.” Product prices were strong for food commodities. U.S. producers were cheered on by Secretary of Agriculture Butz “to plant fence row to fence row,” promising the end of supply controls, long an integral piece of U.S. farm policy. With strong prices came a rapid run-up in U.S. farm asset values. The resulting increase in the value of farm assets fulfilled lenders’ security requirements for an increasingly capital-intensive, expanding California agriculture. Worldwide market demands collapsed later in the 1970s, but U.S. farmland values continued to rise into the early 1980s, in part due to negative real interest rates. Farmland appreciation, adjusted for inflation, over the period 1958–1978 was nearly 80 percent while common stocks lost 20 percent and cash lost nearly 50 percent .

Such information spurred substantial investments in U.S. and California farmlands by individuals, institutional investors, and even foreign investors, creating a price bubble that would collapse in the mid-1980s.Nationwide, the index of farm real estate values was 245 percent more in 1980 than in 1970. Because California agriculture had not benefited as greatly from rising basic commodity demands worldwide, the 1980 farm real estate value for California was only 110 percent higher than the 1970 value. Irrigated land increased more than non-irrigated land, and there were relatively larger increases in value in the San Joaquin Valley than in the Sacramento Valley. Some permanent plantings exhibited excessive land price escalation. Almonds and grapes were two permanent crops that attracted significant investment during the 1970s.Commodity Example – Almonds. Almonds were aggressively planted in the San Joaquin Valley beginning in the late 1960s. Non-bearing acreage amounted to more than 60,000 acres for all but two years from 1968 to 1982, and bearing acreage quadrupled from about 100,000 acres in the mid-1960s to 400,000 by the mid-1980s. Yields increased from three-quarters of a ton per acre to one ton and more. Exports expanded rapidly as supplies increased, accounting for about two-thirds of the crop by the end of the 1970s. The per-acre value of San Joaquin Valley almond orchards increased from $2,250 in 1970 to a peak of $8,570 per acre in 1983 before the investment bubble burst. Within five years, the average value for almond-orchards would fall by 40 percent to $5,200 per acre. Older marginal plantings in northern areas became uneconomical and were removed,large plastic garden pots further accentuating the shift of production to the San Joaquin Valley. Total bearing acreage stabilized in the range of 400,000 to 430,000 acres from the mid-1980s to the mid-1990s. Commodity Example – Grapes. Grapes also attracted significant investments with most of the expansion also taking place in the San Joaquin Valley. The bearing, producing acreage of wine grapes statewide was between 120,000 and 130,000 acres for a long period—from the mid-1950s through the decade of the 1960s. As consumers expressed increasing interest in California wines, non-bearing acreage skyrocketed, amounting to 25,700 acres in 1970, 54,000 in 1971, 104,200 in 1972, and 149,000 in 1973. Most of the new non-bearing acreage in 1973 was in the San Joaquin Valley and in the emerging central coast wine-growing region . The statewide bearing acreage of wine grapes rose sharply from about 132,000 in 1970 to 318,000 by 1977. Another bubble arose. The peracre value of San Joaquin Valley wine-grape vineyards increased from $1,475 in 1970 to a peak of $9,770 in 1982 before a precipitous drop to only $4,000 by 1986. The appearance of surplus wine grapes also affected the fortunes of producers of Thompson Seedless grapes . Raisin vineyards had increased in value from $1,550 in 1970 to $10,840 per acre in 1980, but by 1986 their decapitalized value was also only about $4,000 per acre. Lesser-quality San Joaquin wine grapes proved to be of little interest to the wine industry given the increased supply of superior-quality grapes emanating mainly from coastal production regions.

Central coast vineyards rose in value and, after only a modest adjustment, rose further to more than $20,000 per acre by the 1990s. Prices also escalated in premium north coast production areas. By the end of the 1970s, substantial investments in perennial crops pointed toward the first of the epoch’s “ups and downs,” concluding with a mid-1980s collapse of land prices. Readjustment would affect producers across the length and width of the state.The decade of the 1980s began with the apparent over productive capacity of U.S. and California agriculture. Both were unable to respond to the loss of newly gained export markets and general weakening of world economic conditions following the energy price run-up of the mid- 1970s. Plus, some remaining groundswell from the 1970s continued in California as investment funds sought higher returns in agriculture, further contributing to unprecedented plantings of permanent crops. Commodity prices fell, input prices and interest rates rose, export demand turned down, and farm income declined. Even though it was evident that basic commodity prices were low, some apparently thought that California specialty-crop producers might be immune to agriculture’s declining economic fortunes, but that obviously was not to be. The farm financial crisis began in the Midwest but gradually affected all of U.S. agriculture, including California’s, where the impact was delayed and of lesser magnitude. Farm incomes fell in the face of high debt loads incurred in the land-buying and investment binges of the 1970s. Highly leveraged farms and farm investments were particularly vulnerable to sharp changes in economic fortunes. Consequences included rapid and deep decapitalization of assets, bank foreclosures of farms and ranches, and secondary and social impacts that permeated much of the economy. From 1982 to 1987, land values fell by as much as 60 percent in Iowa and Minnesota and by at least 40 percent in most Midwest and Great Plains states. California land prices fell by a lesser amount—28 percent on average. They would later improve for specialty-crop land but not for widely available field-crop lands that lacked higher and better use potentials. The mid-1980s was a period in which California agriculture sought to right itself from the fallout of the financial crisis. Lenders reevaluated behavior that had resulted in overextended lines of credit that had to be “worked out” following the crisis. Some producers maintained that credit was rationed, but lenders maintained that ample credit was available for applicants with portfolios reflecting appropriate credit risk. Cooperatives came under increasing pressure to yield economic returns commensurate with those of other outlets. Growers sought more immediate economic returns, in part to satisfy lenders’ operating loan requirements. Rising environmental concerns provided additional challenges regarding rice straw burning, use of chemicals, endangered species, and more balanced water use among agricultural, municipal, industrial, and environmental-use claimants. Structural adjustment within the processing sector occurred as older plants, many of which were located in urban and urbanizing areas in Southern California, the San Francisco Bay Area, and the Sacramento region, closed. Prices gradually rose and markets strengthened by mid-decade with rising domestic demand and expanded exports to Europe and Asia.

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A different kind of adaptation among edge growers is to change the commodities grown

Anticipating either that they will have the chance to sell their land for development or that surrounding urbanization will restrict their farming activities, farmers in such situations avoid continuing investment in their enterprises with capital improvements, new technologies, and management time and energy. This uncertainty about the future may in fact serve as a self-fulfilling prophesy, pushing landowners to seek development deals and thus accelerating the rate of farmland conversions in high growth areas. In the interim, much farmland may be idled or underutilized, production shifted from more to less intensively cultivated crops, and individual farm parcels bypassed or surrounded by development. For California farmland owners, the annexation plans of nearby cities are a key sign as to whether or not agriculture is likely to survive in particular areas . Research in other states suggests that urban-related uncertainties often lead to inefficient land use .Not all agricultural landowners in edge locations give up on the future, accepting what others regard as the inevitable demise of productive farming in their areas. There are sufficient stories of individual farmers continuing to invest in and aggressively manage their edge properties to suggest that continued farming in the shadow of urbanization is an important pattern for California agriculture. One reason is that not all edges experience ongoing development pressures. Even in high growth regions, California cities do not grow out in all directions at the same time; rates of expansion also are often gradual, allowing years of stability to some edges. Some landowners thus are unrealistic in anticipating that the path of urban expansion in their area will give them the near-future opportunity to sell their land for development.

In a guide to the easement option for California agricultural landowners,growing raspberries in pots the authors estimate that more than three-quarters of Central Valley farmland “cannot realistically be expected to develop to urban uses within the next 40 years” . Yet even in stable edge areas where agricultural operations are likely to continue indefinitely, the very proximity to residential and other urban land uses usually requires some degree of adjustment on the part of farmers. Operating in the shadow of urbanization demands more in farm management skills and the use of technology, according to some accounts. These abilities and the willingness to adapt and continue to farm in urban-influenced areas are not equally distributed among farmers in such locations. Age and family circumstances play a role.A study of dairy farms in a Hudson Valley area of New York experiencing growth pressures, finds that younger operators with fewer family problems were more likely to stay in business at that location and adapt their operations to the urban environment . Adaptations include various kinds of changes in production practices to minimize negative impacts on urban neighbors and to secure crops and equipment from vandals and trespassers. Integrated Pest Management techniques for reducing or controlling the use of pesticides and other chemicals are widely used by California farmers, drawing from a large body of university and private sector research. IPM covers both biological and engineering innovations, including investment in new spray equipment . Other changes include muffling pump motors, measures to reduce dust, and avoiding late-night and early morning operations that are noisy. Because of these and other adaptations, production costs for edge farming are usually higher than in other locations, whether because of equipment investment or the inefficiencies created by operational changes.One example of urban-influenced adaptation is provided by the experience of Southern California’s poultry farmers during the 1980s.

They invested in new types of buildings to remove laying hens from the floor and thus isolate waste material, changed procedures for drying and disposing of waste, landscaped the areas around poultry housing, and improved fencing and installed alarm systems to reduce vandalism and theft . Some poultry farms in the region chose instead to sell their land for development and relocate in more remote locations, investing some of their proceeds in new facilities—the ultimate strategy by farm operators impacted by urban growth. Generally this means shifting to higher value commodities, or to those that are less vulnerable to urban impacts. Commodities that produce more income per acre, such as tree, ornamental, and vineyard crops, also typically involve more intensive and expensive cultivation practices. But the motivation for shifting in this direction is the already higher costs of farming in urban-influenced areas, including the land costs for farms that acquire more land to expand their operations . Such adaptations allow some productive and profitable agricultural operations to continue in locations highly impacted by urban growth. This is suggested by changes in farm operations in several of California’s largest metropolitan counties recorded in the half century between 1950-2001, a period of considerable population growth and farmland conversion. Table 3 shows the changes during this period in population, agricultural market value, and top four farm commodities for five of the state’s eight counties with more than 1 million residents . Located in coastal areas, they include the four most populous counties of California. All five counties recorded a substantive shift in dominant commodities over the half century, with nursery products or flowers taking over the top spot. Citrus, poultry, dairy products, and field crops—ranking commodities in 1950—were largely eliminated from the top four spots by 2001.The significance of the shift to nursery plants is that they are often grown in greenhouses, enclosed environments that limit impacts on urban neighbors and are relatively secure from vandalism and other encroachments. Nursery products also have a ready market in nearby urban areas. Table 3 also reveals the continued importance of agricultural to local economies in four of these metropolitan counties.

With the exception of Alameda, all had farm market values of at least $250 million in 2001. Even Los Angeles County made this list in 2001, due to $152 million in nursery sales, although the agricultural significance of this most populous California County dropped greatly from the late 1940s when it was the state’s top producer in market terms. In 2001 Los Angeles ranked 27th in farm value among California’s 58 counties. San Diego County stands out as the only county in this sample with an increase in farm market value during 1950-2001 that exceeded the rise in California’s consumer price index during this half-century. In 2001 San Diego ranked eighth in the state with a market value of $1.3 billion, fueled by more than $700 million in nursery and flower production and $138 million in avocados.In pointing to the survivability of farming in metropolitan areas, however, these numbers are more suggestive than conclusive. The “metropolitan” designation is only a rough and imprecise indication of the extent to which local agriculture is influenced by urbanization. The counties in this small sample in fact contain vast rural areas, leaving open the possibility that many of the most productive farms are not close to urban development. Also not examined in this analysis is the extent to which commodity shifts are the result of other factors, including market forces and water supply.Research in several eastern states supports the survivability thesis for urban influenced farming. The common generalization from several studies is that urban proximity can provide profit-making opportunities as well as problems for farmers, considering the potential for direct marketing, other forms of access to urban consumers, and off-farm income for operators. . But only certain kinds of intensely-cultivated farms,plastic plant pot including vegetable producers, seem to benefit from such locations . A USDA review of the available information on farms in metropolitan areas characterizes them as smaller, producing more per acre, more diverse, and more focused on high-value production than farms in non-metropolitan areas .Land use policies and regulations can be seen as largely proactive efforts to direct the location and form of new urban development in ways that would minimize impacts on agricultural activities. This is the general intent of policies that call for keeping development away from agricultural areas, in particular restricting residential growth in the countryside and directing it instead to existing cities, either as infill development or as incremental additions to municipal areas as cities gradually annex adjacent territory. Some conversion of farmland is inevitable in this process where cities are surrounded by agricultural uses, as throughout the Central Valley. But the assumption is that this is preferable to allowing building in unincorporated areas, because city development occurs at relatively high densities that convert less farmland in relation to population housed, it is less costly in public infrastructure terms, and it is more likely to produce solid and less exposed edges with farming. Also cities that are surrounded by agricultural land of varying quality and productivity have the option of directing their expansion away from the best farmland. City-oriented growth strategies are supported by the LAFCO process and county city agreements on the location of future urban development.

LAFCOs are California’s boundary control agencies at the county level, semi-independent boards that have the power to review, deny, or change city plans to annex territory and to designate their future growth areas . LAFCO actions, guided by orderly growth and farmland projection objectives, are a major restraint on extensive sprawl. Some counties and cities in agricultural areas have negotiated agreements that divert urban development from unincorporated areas to city areas, usually in return for financial considerations that allow the county to share in municipal growth revenues . The two land use policies that most specifically address edge issues are agricultural buffers and mitigations imposed on new development for the loss of farmland or to limit negative impacts on farming. The two are closely related, since buffers are a type of mitigation frequently recommended by the environmental reviews conducted by county and city governments of proposed urban projects. Buffers essentially create a separation between agricultural and urban uses, using barriers or distance to minimize negative impacts on both sides of an edge boundary, especially the effects of chemical drift from farming activity. Agricultural buffers come in different forms—natural barriers created by landscape features such as waterways, roads, landscaping, walls, residential setbacks, open space greenbelts, and combinations of various types. Key issues in their design and creation are their permanence, maintenance, and which landowners—developer/homeowner or farmer—provide the land or barrier. Although the general plans of many California counties and cities call for use of buffers to protect farmland, the implementation of the technique and application to specific urban projects is quite spotty, as Mary Handel noted in a 1994 M.S. thesis in Community Development at UC Davis. Especially controversial are the desired widths for setbacks and greenbelts, with farm chemical applicators and other agricultural experts calling for the biggest possible separations while urban developers and city governments argue for smaller widths because of land cost considerations. In Handel’s study of buffer use in 16 counties and 6 cities, designated widths range between 50-800 feet. She also finds great variations among farmers and urban neighbors in the perceived effectiveness of different forms of buffers to limit specific negative impacts. For example, farmers generally judge setbacks or open space buffers as ineffective in dealing with trespass, vandalism, litter, theft, and dogs while urban residents see them as generally effective in reducing chemical drift, odor, and dust from farm operations . More recently, the Great Valley Center published a short guide on agricultural buffers for urban planners .As contrasted with the land-use control approach of trying to head off edge problems by influencing the location and design of urban development, other strategies seek to deal more directly with farm-urban neighbor tensions, often after they have emerged. Government policies and programs in this category include right-to-farm ordinances, California’s extensive regulation of pesticides and other agricultural chemicals, and restrictions on farm animal facilities driven by clean water policies. When first adopted by California local governments in the late 1980s after enabling state legislation, right-to-farm ordinances were seen as a promising tool for protecting routine farm operations from nuisance law suits and complaints by urban neighbors. The central feature of most such local laws is a disclosure requirement—notifying home buyers of parcels adjacent to farms of the possibly negative effects of agricultural operations. In this way, the assumption goes, new residents especially would learn about the realities of modern farming and would be less inclined to complain or even go to court over sprays, dust, odors, noise and other results of nearby agriculture.

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The overall synthesis of the trehalose hydrogel was modified from a previously reported procedure

Multi-substituted styrenyl-trehalose prepared during the monomer synthesis acted as an efficient cross-linker to form a hydrogel after redoxinitiation with APS/TEMED , eliminating the need for additional cross-linkers or chromatographic purification of the monomer. After formation, the crude hydrogel was extensively washed via Soxhlet extraction in order to remove any unreacted trehalose and other residual non-polymerized components in the precipitation mixture, producing a colorless gel. Finally, the gel was lyophilized to produce a white powder. Originally, this method only produced hydrogel with an overall low yield of 17 %,which is too low to be relevant for use. Thus, we systematically optimized for the hydrogel synthesis to increase scale and sustainability. To increase the yield, we decreased the equivalents of trehalose from 5 to 3.33, effectively increasing the ratio of 4-vinylbenzyl chloride to trehalose. LC/MS of the dried solids confirmed that the product contained a mixture of mono- and di-substituted styrenyl-trehalose with various regioisomers at 94.1 % and 5.9 %, respectively . Higher order components such as tri-substituted trehalose were not observed by LC/MS either because they too dilute to detect or they were not ionizable. We then degassed the monomer/cross-linker and initiator solutions prior to gelation. This gave an overall reaction yield of 88 %. The increase in 4-vinylbenzyl chloride allowed for an increase in modified trehalose in the crude trehalose monomer/cross-linker mixture , which in turn resulted in a higher yield. When this improved synthesis was scaled 100-fold, it was carefully monitored with regard to reaction conversion, solvent removal, and drying to ensure that trehalose was sufficiently modified for gelation. With these necessary modifications, such as slow precipitation, the multi-gram reaction gave an overall yield of 75.6 %. As the goal for reaction yields in industry is above 70 %, this yield is industrially-promising.The final product demonstrated a storage modulus that was larger than the loss modulus as determined by a rheology frequency sweep with constant strain,maceta de plastico cuadrada indicating that the material passed its gel point and demonstrated solid-like behavior.

The swelling ratio was calculated as 15.63 ± 0.71 indicates that the material absorbs water many times its dry weight, as is characteristic of hydrogels.Though both a high yield and scalable synthesis were demonstrated, there are other factors that are desirable for industrial use, such as minimal use of hazardous materials, especially halogenated and toxic solvents.The precipitation step to isolate the crude reaction mixture was originally undertaken in hexanes, a neurotoxin,and DCM, a carcinogen.To replace these solvents, we tried to eliminate the precipitation step. This attempt was irreproducible and therefore not explored further. We next endeavored to replace hexanes and DCM with sustainable solvents of similar polarities. Based on waste, environmental, health, and safety issues, GlaxoSmithKline has produced a guide which scores solvents on sustainability.The solvents are assigned colors, red, amber, or green, where red is reserved for problematic solvents, such as hexanes and DCM, green is for the more sustainable solvents, and amber is for solvents in between the two extremes. Heptane and toluene are amber solvents with similar polarities as hexanes and were therefore envisioned as substitutes for hexanes. Acetone, an amber solvent, butanone, a green solvent, and ethyl acetate, a green solvent, with higher polarity, were explored as substitutes for DCM. Solvent ratios were varied to ensure miscibility of DMSO. Acetone, ethyl acetate, and butanone were too polar to sufficiently precipitate modified trehalose. Yet, when combined with heptane or toluene, gels formed after the precipitation step . The overall yields of these gels were lower because of the employed washing method. Material is lost when decanting and replacing solvent versus Soxhlet extraction; this washing method was necessary due to the small scale of the reactions.Precipitating into green/amber solvents gave similar yields , with the exception of butanone/heptane . The most sustainable precipitation that gave the highest yield, ethyl acetate/toluene , was scaled 100-fold and then used for gelation to give a 64.1 % yield. This yield can likely be optimized further with industrial equipment and shows potential as a greener alternative to the original synthesis.

It is important to note that although 4-vinylbenzyl chloride exhibits acute toxicity, we previously demonstrated that once reacted to form styrene-modified linear trehalose polymers, the material is cytocompatible and similar styrenyl polymers are nontoxic in vivo. 23With an optimized synthesis, the gels were tested for their efficacy in protecting animal feed enzymes during the conditions encountered in the feed pelleting process. Steam pelleting is a common practice as it improves feed efficiency by decreasing nutrient degradation.Frequently, temperatures reach 60 °C to 90 °C and most enzyme activity is lost at such temperatures. A method to stabilize these enzymes during pelleting that offers a dry, easy-to-handle final form of feed with active enzyme is essential to the livestock industry. We decided to investigate phytase, xylanase, and b-glucanase because 60 % of the global feed enzyme market is attributed to phytase, while 80 % of the global carbohydrase market is xylanase and b-glucanase.Phytase hydrolyzes phytate, which is the storage form of phosphorus in the feed, releasing digestible phosphates and chelated minerals.Xylanase degrades the main component of hemicellulose present in plant cell walls, b- 1,4-D-xylan, into xylose.b-Glucanase cleaves 1,4-b-D-glycosidic linkages in b–glucan, allowing the release of smaller saccharides from cellulose.For xylanase, the activity beyond 100 % retention invoked by the addition of trehalose hydrogel to phytase and xylanase may be attributed to the gel scaffold or trehalose moieties stabilizing or enhancing the protein/substrate binding and/or stabilizing the protein to the assay conditions that includes a lyophilization step. The former has been observed for glucose oxidase where the addition of trehalose augmented the affinity of the substrate for the enzyme,36 and for enzymes horseradish peroxidase and b-galactosidase upon interaction with trehalose polymer excipients.We investigated the activity of xylanase after incubation with hydrogels, without heat. Indeed, xylanase activity was greater than 100 % by the addition of even 1 weight equivalents of trehalose hydrogel .

Given that trehalose hydrogel alone has negligible signal from the enzyme assays, these results suggest that the trehalose hydrogel could be stabilizing the enzyme even without the addition of heat. The heated xylanase data was normalized to the results in Figure 2.7, and trehalose hydrogel still demonstrated substantial stabilization of the enzyme . We then considered the activity of xylanase when incubated with free trehalose without heat. We observed greater than 100 % original activity, albeit with no statistical difference compared to xylanase activity without additive . It follows that the gel scaffold or multi-valent effect of polymerized trehalose, beyond that of free trehalose, could be responsible for the improved activity of xylanase when incubated with hydrogel. We investigated the increase in activity of xylanase further by testing the aggregation state of xylanase subjected to heated assay conditions with or without hydrogel additives and comparing the results to a control subjected to all the assay conditions except for the heat step. An additional sample of fresh xylanase was prepared. At 1 mg/mL xylanase concentration in 0.1 M sodium acetate, all conditions were evaluated by dynamic light scattering . The results demonstrated small hydrodynamic sizes for fresh xylanase as well as xylanase subjected to heat with hydrogel additive. However, large increases in hydrodynamic size , indicative of aggregate formation, were observed for free xylanase subjected to assay conditions with or without heat. Thus,maceteros reciclados de plastico free xylanase must be sensitive to assay conditions, which includes a lyophilization step, and hydrogel addition stabilizes xylanase to these conditions, thereby likely explaining the greater activity. Trehalose polymers stabilize proteins to both lyophilization and heat by suppressing water crystallization, preventing aggregation and helping to refold proteins,and likely the hydrogels act by similar mechanisms. The release of enzymes within the gel was tested. Phytase was chosen as the model enzyme as it has the highest molecular weight compared to xylanase and b-glucanase and should therefore have the slowest diffusion rate of the three enzymes. The experiment was conducted at pH 6.3 using simulated intestinal fluid,37 and 37 °C to mimic the conditions found within the small intestine of pigs.FITC-labeled phytase demonstrated 100 % release from the trehalose hydrogels within 4 hours . It has been estimated that transit of feed through the small intestines of pigs is approximately 3 – 4 hours.Thus, the release is already within the relevant time frame and will likely be expedited with increased agitation in the gastrointestinal tract. We also demonstrated that the addition of trehalase enzyme had no effect on the release of phytase from the trehalose hydrogels . Trehalase is an enzyme found in the intestines and kidneys of many organisms, including humans and pigs,that catalyzes the conversion of trehalose into two glucose units. Therefore, we hypothesized that trehalase could potentially breakdown trehalose within the hydrogel, catalyzing its degradation and release of sequestered cargo. However, previous studies demonstrate that disaccharide mimics are completely buried within the trehalase enzyme, requiring significant conformational changes for substrate entry into the enzyme’s active site.Thus, it is likely that the interaction between trehalose linked within the hydrogel and trehalase’s active site is entropically unfavorable or sterically forbidden, preventing degradation. Note that the increase in trehalase concentration from 3.5 U/mL to 1000 U/mL in this experiment still had no effect on phytase release .Lastly, we explored whether trehalose polymers could similarly stabilize whole cells.

A linear trehalose glycopolymer with the same backbone as the trehalose hydrogel was evaluated for its ability to stabilize bacteria to lyophilization, which is often used to preserve and store biological samples, but is also known to negatively affect protein and cell viability .The trehalose glycopolymer was added as an excipient to a strain of BL21 E. Coli bacteria under lyophilization stress. Cell proliferation was monitored by measuring the OD600 and was used to determine E. coli survival and, therefore, stabilization. Samples lyophilized in the presence of P3 had lower OD600 measurements compared to with trehalose at an equivalent concentration , but higher OD600 measurements compared to the control . While trehalose has been shown to stabilize cells in a the dry state by maintaining the structural and functional integrity of their membranes through vitrification and bacteria synthesize extracellular polysaccharides in preparation for dehydration,cytosolic trehalose has been shown to be more effective for cell stabilization than extracellular trehalose added as an excipient.As such, it may be necessary to internalize trehalose, as the free disaccharide or the glycopolymer, within the cell to see more significant stabilization. All reagents and solvents were purchased from SigmaAldrich or Fisher Scientific and used without further purification unless otherwise noted. Trehalose was purchased from The Endowment for Medical Research and was azeotropically dried with ethanol and kept under vacuum until use. Phytase was provided by Phytex, LLC. Xylanase and trehalase werepurchased from Megazyme. b-glucanase was purchased from Sigma-Aldrich. EnzChek Ultra Xylanase Assay Kit was purchased from Fisher Scientific. b-Glucanase Assay Kit was purchased from Megazyme. Kanamycin-resistant strain of BL21 E. Coli bacteria was provided by the lab of Professor Robert Clubb. 1 H-NMR spectra were performed on an Avance DRX 400 MHz instrument. Liquid chromatography-mass spectrometry experiments were carried out on an Agilent 6350 QTOF ESI with a 1260 Infinity LC and Phenomenex Luna C18 5 µm column and were eluted with a gradient of 5 – 95% solvent B over 20 minutes. To determine hydrogel mechanical properties, an AR 2000ex rheometer in parallel plate geometry was used with an 8-mm diameter stainless steel, cross hatched upper plate and 60 mm stainless steel, cross hatched lower plate cover, at 22 °C, constant strain of 1%, and an angular frequency range of 0.1 to 10 rad s-1 . Gels were swelled for 72 hours in Milli Q water, trimmed to 8 mm diameter and approximately 1 mm thickness, and carefully blotted to removed excess water before measurements. Absorbance measurements to determine the degree of fluorescein isothiocyanate labeling of phytase and concentration of protein were conducted on a Thermo Fisher Scientific NanoDrop 2000 Spectrophotometer. Other absorbance and fluorescence measurements were taken on a Tecan Infinite M1000 plate reader. Dynamic light scattering measurements were conducted on a Malvern ZetaSizer Nano at 1 mg mL-1 protein concentration in 0.1M sodium acetate buffer.Under an inert atmosphere of argon gas, sodium hydroxide pellets were added followed by dimethylsulfoxide .

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Surface water originates from both on farm and off farm sources

Globally and within the United States, the cost of energy associated with crop irrigation is increasing as growers convert to higher pressure systems and pump more groundwater from greater depths as water tables continue to drop . Additionally, parts of the electric grid are under a significant or increasing amounts of strain due to elevated demand and ambitious Renewable Portfolio Standard targets . Consequences of increased reliance on groundwater pumping extends beyond the energy implications and can results in irreparable environmental damages. Those consequences include aquifer contamination by seawater intrusion or depletion beyond the point of recharge, land subsidence, infrastructure damage, and harm to groundwater dependent ecosystems . Demand management strategies such as Demand Response can help farmers better manage electricity consumption and unlock new revenue streams while providing benefits to the electricity grid and the environment . Traditionally DR has been a strategy primarily used to shift and/or lower electrical loads during peak hours . In recent years, due to evolving grid needs, the value of DR has expanded beyond load shifting to include various services as dictated by the grid needs . The goal of this paper is to establish a clear understanding of current and future needs of the electricity grid, available electricity market mechanisms, and electricity consuming/generating equipment on farms. This paper aims to achieve that clear understanding by putting forward a standardized framework similar to the illustration shown in Figure 1, which allows farm equipment to be mapped to respective grid needs through available market mechanisms. This mapping will allow for the widespread adoption of DR within the agricultural industry by removing a significant knowledge gap that exists between the farm, utilities, and the grid. Such analysis can also identify market mechanism that are required for addressing current and future grid needs and are not captured through existing ones. While there are promising technologies under development aimed at increasing the reliability of agricultural DR participation,arandano azul cultivo little attention has been given to educating the farmer, utility/DR aggregator, and grid operator about the electricity grid, electricity consuming/generating equipment on farms, available electricity market mechanisms, and how all those connect and interact with each other.

As discussed by Aghajanzadeh, et. al. , agricultural loads, with their potential flexibility, can help reduce their energy cost, and improve grid stability as energy markets move into a future of increasingly distributed and renewable electricity generation. However, agriculture’s operational constraints, conventional irrigation system design and management standards, and low penetration of in field automation limit farms from taking advantage of more flexible energy and water use strategies that could benefit the grower, utility, and the grid. Several studies have highlighted the technological and operational hurdles for widespread adoption of DR in the agricultural sector. Olsen, et. al. provide foundational information on the status of agricultural DR in California . In this work Olsen et. al. identified several factors as barriers for farmers to participate in existing DR programs. Those barriers include insufficient irrigation capacity, lack of communications, controls, and financial incentives. Other factors hindering DR adoption include inflexibility of water delivery, application methods, and labor. According to Pacific Institute and Ringler et. al., the agricultural industry has the opportunity to improve its bottom line by tapping into new revenue streams such as DR incentives or implementing energy and water efficiency practices that reduce farm operation costs . However, agricultural demand management programs have proven to be unsuccessful in facilitating the needs of the farm and helping the utilities manage their demand and reduce cost . Many DR programs offered by electric utilities are developed with no regard to on farm operational constraints. Many customers may not even be aware of available DR enabling technologies or operational measures . Marks et al., also point out that the complex process of DR program enrollment, enablement, and participation has led to unsuccessful adoption of existing demand management programs within the agricultural industry .The electricity grid has evolved and integration of intermittent renewable sources such as wind and solar has made balancing the grid more complex. Figure 2 shows the generation mix of California’s grid under a 50% RPS scenario which is expected to be achieved by the year 2030 . Intra-hour variability and short-duration ramps are one of the immediate challenges faced by a 50% renewable California grid. In a 50% RPS scenario, thermal power plants need to ramp down as solar resources come online in the early hours of the day . However, they cannot drop to zero since a minimum capacity need to remain spinning for contingency as well as the evening ramp up, and in the absence of cheap energy storage, excess solar generation needs to be curtailed in order to maintain grid stability . As the solar resources stop generating electricity in the evening hours , thermal power plants need to ramp up to make up for the lost solar generation. The ramp up to meet the evening peak will be more pronounced due to lower than usual net demand due to high solar penetration .

Market mechanisms are platforms that connect electricity end users, generators, and grid operators. These mechanisms are needed to ensure that the needs of the electric grid are satisfied while entities providing services to the grid are fairly compensated. While more intermittent renewable sources are integrated into the grid as dictated by the RPS targets, grid operation becomes more complex thus giving rise to more complicated and nascent market mechanisms. While new systems such as Automated Demand Response 3 are seen crucial in addressing the challenges faced by the future grid, today’s wholesale DR systems seem experimental, and retail DR systems typically work on slow time scales as open loop systems to address peak load reduction . In order to address the variable generation mix and the dynamic demand of electricity, new market mechanisms are introduced and existing mechanism are constantly modified. The constant evolution of market mechanisms has led to a lack of understanding and a knowledge gap in how the electricity markets operate and the ways through which end users can participate in them. Moreover, the DR needs and availabilities of different actors may evolve over time needing constant modification of existing market mechanism which can further widen this knowledge gap. Another layer of complexity is the hardware requirements and communication protocols used for each market mechanism and by various service providers . This will leave many end users unaware of technological or operational measures available to them . Although this paper does not discuss communication protocols, telemetry, and settlement metering requirements, it lays the groundwork for further exploring those requirements by providing conceptual DR participation pathways. All DR service types fall into two main categories. Demand Side or load modifying resources, which reshape or reduce the net load curve; and Supply Side or supply resources, which are integrated into the Independent System Operator energy markets. Figure 8 summarizes these two categories and requirements for participating in each category.Energy efficiency and load management programs offered through the utilities in many US states are collectively called demand side resources. Such retail DR systems typically work on slow time scales as open loop systems to address peak load reduction . Currently agricultural loads can only participate in demand side DR by enrolling in a TOU, DR,macetas 25 litros or ADR program offered by their local utility.

Any resource that transacts with the electricity grid by providing a bid, price, and duration with short or no notification is treated as a generator and required to adhere to the same requirements . Transaction for such resources happen in wholesale ancillary services markets, operated by the ISO. This type of advanced DR will become more valuable over time, as the ISOs across the US integrate additional renewable energy sources and curtailment becomes more significant during the midday hours . There are currently no mechanisms in place that allows agricultural loads to directly provide supply side DR. Agricultural operations consume a variety of energy types for different purposes: directly as gasoline, diesel, natural gas, propane, or electricity , and indirectly as fertilizer or pesticide . Given that the focus of this paper is providing DR services to the grid, only direct electricity consumption is discussed. The number of farms producing electricity on site through renewable sources doubled between 2007 and 2012 . Farms that produce their own electricity are linked to energy markets on both the supply side and the demand side. This exposes farms to volatility in energy prices as energy consumers and uncertainty of revenue from the production of electricity generated on site and sold back to the grid . For example, electricity prices affect the costs of crop irrigation due to water pumping but also affect the value of renewable power generated on farm . While similar analysis can be carried out for other energy types consumed or generated on a farm, the focus of this paper is only on direct electricity consumption or generation on a farm specifically for the purposes of crop irrigation. Agriculture is a major user of ground and surface water in the US, accounting for approximately 80% of the nation’s consumptive water use. In many Western drought prone states that number increases to 90% . In Western states, irrigation provides most of the crop water requirements, while in eastern areas irrigation is largely supplemental . Unlike turf irrigation, which is mostly done at night, irrigating farms require a constant supply of water to meet crop requirements . Therefore, a large amount of agricultural pumping occurs during period of high evapotranspiration4  including summer afternoons which are prone to having the highest levels of ET. Irrigation pumps are primarily powered by electricity. According to 2013 Farm and Ranch Irrigation Survey, 85% of irrigation pumps are electric and only 13% of pumps are powered by diesel . Since most pumps on farms use electricity to convey water, the large water pumping demand for agriculture can be translated to large electricity consumption. About 70% of the electricity consumed on a farm is due to water pumping .

Electricity is consumed on a farm to either pump water out of the ground, divert surface water, or pressurize water for irrigation applications. While pumps use the majority of the electricity on the farm, there are other equipment and generation sources that complicate the analysis of energy consumption on a farm. Those equipment include solar panels, variable frequency drives on pumps, and water storage. Presence of those components can affect the timing and manner of electricity consumption and its controllability on a farm. To take full advantage of available loads on farms, their DR potential, level of automation, response time , and required notification time should be characterized. Figure 10 illustrates a generic representation of available assets on a farm as well as the electricity and water flows. Figure 10 is representative of a generic farm and does not include all possible equipment found a farm . This paper focuses on water related energy consumers on a farm; therefore, all the equipment listed in Figure 10 and the rest of this analysis include equipment that are involved in water conveyance, pressurization, and storage. In the following sub sections, each relevant piece of farm equipment will be analyzed in detail, including its manner and timing of energy use, level of automation, and ways through which they can impact electricity consumption on a farm. A summary of farm equipment characteristics discussed in this section is presented in Table 2. In order to integrate agricultural loads into the grid their level of automation, response time, and demand flexibility need to be characterized. Three levels of automation is assigned to each farm end use . Surface water pumps divert water from surface water sources and distribute the water throughout the farm for irrigation purposes.On farm surface water comes from ponds, lakes, or streams and rivers, while off farm water sources are generally supplied to the farm through local irrigation districts; mutual, private, cooperative, or neighborhood water delivery companies; or from local or municipal water systems . Surface pumps are low static head systems with most of the energy expended to overcome the dynamic head. As of 2008, 52% of irrigation water needs were satisfied through surface water sources, but that number has been decreasing in recent years with groundwater withdrawals increasing to make up for the surface water shortage.

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Technology is likely to be the solution to many of these new problems as well

Furthermore, the percentage increase in gross sales is reduced when growers with sales above the $5 million reporting ceiling accurately report increased acreage but do not report the corresponding increase in gross sales, only the requisite $5 million. Organic fruit crops posted a sales increase of 28 percent between 1998 and 2002, with a 40 percent increase in acreage . The most important commodities for sales growth were strawberries, raspberries, wine grapes, dates, avocadoes, apples, and peaches. Organic wine grapes increased in sales by over $4 million and acreage expanded by over 3,000 acres.In contrast, sales of table grapes almost halved over the period while acreage reduced only slightly.The most important nut crops remained almonds and walnuts, with sizeable increases in sales and acreage for both.Field crops grew in acreage from 1998-2002, with the number of farmed acreage increasing by over 50 percent . One third of the increase in acreage is attributable to pasture and range land paralleling the increase in livestock and dairy production. Another 25 percent reflects increases in rice, alfalfa, and wheat acreage. Rice remained by far the most important field crop during the period but with stagnant sales at around $7 million. Alfalfa was the second most important field crop with sales increasing from less than half a million dollars in 1998 to $1.3 million in 2002. The importance of field crops to organic agriculture remained small, falling from 6 percent of sales in 1998 to less than 5 percent of sales in 2002. This decrease in importance is explained by an absolute decrease in sales over the five year period in almost every region. The decrease in importance is also related to the dramatic increase in sales of livestock, poultry and products. Sales from livestock, poultry,macetas 30l and related products increased by 389 percent over the past five years, although they remained less than 3 percent of the organic industry. Dairy production increased from $4 million to over $11 million.

Sales of organic meat were not permissible prior to 1998 due to differential labeling requirements for organic meat and other foods. Sales of organic chicken reached over $6 million in 2002 with beef and turkey each at about $300,000. Organic eggs sales were $3.6 million in 2002. California agriculture today is known around the world for its diverse product mix, remarkable productivity, and technological sophistication. It is also known for its large-scale farm firms, vertical coordination in food marketing and processing, and, less happily, its environmental problems and farm-labor concerns. The development and adoption of improved technology has been a central element in all of the changes during the twentieth century that have led to the marvel that is today’s California agriculture, and the problems that it faces in the twenty-first century. In this chapter we review the role of new technology in the development of California agriculture, emphasizing the period since World War II.First, we document the changes in the inputs and outputs over the 1949-91 period showing the general trend to save land and labor, to increase the use of capital and purchased inputs, and to increase the output of all categories, but especially vegetables, and nursery and greenhouse marketings. Along with the growth in measured productivity, there have been some important changes in the structure of agriculture as well as in the nature of farms and farming, with a trend to fewer and larger, more specialized farms being an important element of the structural change.The second part of this chapter focuses on the evolution and adoption of various technologies in California agriculture. California is a part of the United States, and its agriculture has shared in many general developments such as the mechanical innovations that displaced the horse over the first half of this century, and other nationwide chemical and biological advances; still, California agriculture remains unlike farming in most of the rest of the country in many ways.

We describe major changes in the elements of technology that have facilitated California’s agricultural development, using examples of mechanical harvesters, pest-control strategies, and irrigation technology. We also discuss some examples of integrated systems involving multiple elements of production technology and marketing—such as the development of tomato varieties that could withstand mechanical harvesting, and the development of new strawberry varieties along with pest-control and production technology to match market requirements. In the last part of the chapter we consider the sources of new agricultural technology and the role of government in providing resources for research and development, as well as institutional structures to facilitate private-sector activity.California agriculture today is very different from what it was in the gold rush years and through the early part of the twentieth century. In the early years, even in this century, there were few people to feed within California, and transportation costs and technology were such that perishable commodities were not economic to produce for shipment over long distances to the population centers in the East. The main focus of the state’s agriculture was on producing grain under dryland conditions, either for human consumption or for livestock feed. Feeding horses was a primary role of California agriculture up through the 1920s. The development of irrigation, transportation infrastructure and technology, postharvest storage and handling technology and facilities, food preservation technology, and the growth of the state’s population, along with the replacement of the horse by motorized vehicles, changed all that. The seeds for the radical transformation of California agriculture during the twentieth century were sown in the last decades of the nineteenth century. In the first chapter of this volume, Olmstead and Rhode provide an overview of the history of California agriculture; they emphasize the role of technology.1 We build on the foundation laid in that chapter. The key elements of technical change have included mechanization , irrigation, agricultural chemicals , improved varieties and other biological improvements, and improved management and information systems. These changes in technology have been made in conjunction with changes in the output and input mix, for related reasons.

Indexes of output in California agriculture in the post-World War II era are shown in Table 1. In terms of total agricultural output, California farmers produced over three times as much in 1991 as in 1949 . Different components of agriculture grew at different rates at different times. For instance, greenhouse and nursery products grew almost tenfold , while output of field crops grew much more slowly . There was considerable variation within individual categories, with some individual products growing very rapidly and others shrinking to negligible amounts. Thus the composition of California production changed markedly over the post-war period. Higher-valued products such as vegetables, greenhouse and nursery products, as well as fruits and nuts, account for a larger share of the value of agricultural output in the 1990s than they did in the immediate post-war period; the shares of livestock and field crops are smaller, accordingly,maceta 25 litros even though all sectors of California agriculture grew significantly over the period. The use of inputs in California agriculture also changed markedly over the postwar period, as seen in Table 2. California agriculture’s use of purchased inputs more than trebled from 1949 to 1991 . The use of capital services—including physical inputs such as automobiles, tractors, trucks and combines, as well as biological inputs such as dairy cows, ewes, and breeder pigs—grew by over 75 percent from 1949 to 1991 . However, quality-adjusted land and labor use in agriculture declined. Land use fell by 8 percent , while labor use decreased by 10 percent . Across all input categories, the index of input use increased by 58 percent, from 100 to 158.That the 237 percent increase in agricultural output was achieved with only a 58 percent increase in agricultural inputs is a reflection of the changing productivity of those inputs. Expressing aggregate output per unit of aggregate input provides a measure of productivity, as shown in Table 3. Productivity in California agriculture doubled between 1949 and 1991 . This means that, if input use had been held constant at the 1949 quantities, using 1991 technology would have resulted in twice as much output as using 1949 technology. Alternatively, to produce the output in 1991 using 1949 technology would require using twice as many inputs as were actually used. In other words, more than half of 1991’s agricultural output is directly attributable to improved technology; and less than half is attributable to conventional inputs. Growth rates of output, input use, and productivity have varied widely from decade to decade. The period of greatest productivity growth was during the 1970s when global commodity markets boomed. The 1980s was a decade of relatively slow growth in output and productivity. Based on similar data ending in 1985, Alston, Pardey, and Carter estimated that the rate of return to public-sector agricultural R&D in California, to which much of that productivity growth could be attributed, was around 20 percent per annum in real terms.3 Complete, specific data on inputs, outputs, and productivity in California and U.S. agriculture, comparable to those in Tables 1 through 3, are not yet available for the years after 1991.However, the data that are available suggest that the 1990s reflected are turn to a more-normal rate of productivity growth in California, sustaining the longer-term average rate, in the range of 2 percent per annum.Mullen et al. applied California’s 1949-1991 average annual agricultural productivity growth rate of 1.81 percent per year to the period 1949-1999. They found that with 1950s productivity and the actual inputs used, output in 1999 would have been only 42 percent of the actual value of $25.3 billion. Hence, the factors that gave rise to productivity growth since 1950 accounted for $14.8 billion worth of output in 1999 alone. Considering the period 1949-1999, Mullen et al. estimated that if public agricultural R&D accounted for one-sixth of the productivity growth the benefit-cost ratio for public investments in agricultural R&D would still be 6:1 . Changes in inputs, outputs, and productivity in California agriculture paralleled similar changes in other states and around the world, but with some important differences reflecting elements unique to California.

As a result of these changes, farms and farming today are very different from what they were in the early part of the twentieth century. Clearly, new technology has been a major driver in the development of California agriculture—and not just agricultural technology. Important changes off the farm have included improvements in methods of food preservation, storage, transport, and handling, along with general improvements in the transportation infrastructure. A host of other technological changes have been applied on the farm. Many of these have been shared with agriculture in other places, and beyond agriculture. In what follows we emphasize those developments that have been specific to California and important here, focusing for the most part on technology applicable at the farm level.The process of technological innovation in California has much in common with the process of technological innovation in the United States more generally. Nonetheless, there are some unique features. Like other regions in the United States in the early part of the twentieth century, changes in technology in California emphasized the adoption of mechanical technology—improved plows, various kinds of harvesting machines that were initially powered by animal power or steam engines, tractors, and so on. All of these innovations reduced costs, especially labor per acre.4 Such mechanical inventions enabled the establishment of land-intensive agriculture and, together with the Homestead Act of 1862, were crucial elements in the settlement of California. As in the rest of the United States, California agricultural production in the twentieth century has grown primarily through increases in yield per acre. California farmers were early in their adoption of chemical inputs such as fertilizers and pesticides, and swiftly took up more advanced agronomic and biological management practices. Recently, California has become the leader in introducing biotechnology and computerized systems into agriculture.Unlike other states, however, the growth of agriculture in California required diversion of water. From the nineteenth century on, California agriculture emphasized the introduction and adoption of institutions and technology to facilitate irrigated agriculture.The institutions ranged from local collective arrangements for diverting the water to massive state water projects. Technology emphasized physical innovations in delivering water to improve control and efficiency. In California, as in other western states, much emphasis was given to improved irrigation technologies.

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Earned legalization is billed as the compromise between guest workers and legalization

Farmers and worker advocates argued over the details of a revised AgJOBS program that included earned legalization throughout 2000, with farmers wanting more days of farm work to qualify for eventual immigrant status, and worker advocates fewer days. After the November 2000 elections, some worker advocates, noting that both U.S. President Bush and Mexican President Fox favored a new guest worker program, agreed to a compromise that won the endorsement of the United Farm Workers and the National Council of Agricultural Employers. Under this December 2000 compromise, unauthorized workers who did at least 100 days of farm work in the preceding 18 months could qualify for temporary legal status, and they could convert this temporary legal status into an immigrant status if they did at least 360 days of farm work in the next six years. The compromise included freezing the minimum wage that had to be paid to foreign workers for several years and giving farmers the option of providing a housing allowance rather than housing to workers. The AgJOBS compromise came close to Congressional approval in December 2000, but was blocked by those opposed to any type of amnesty for unauthorized foreigners. The atmosphere changed in 2001, especially after U.S. President Bush and Mexican President Fox met in Mexico in February 2001 and agreed to establish a migration working group that was charged with creating “an orderly framework for [Mexico-U.S.] migration that ensures humane treatment [and] legal security, and dignifies labor conditions.” Senator Phil Gramm became the leading proponent of the guest worker-only approach, favoring a program that would permit unauthorized Mexicans already in the U.S. to obtain seasonal or year-round work permits: seasonal workers could return to the U.S. indefinitely,macetas de plástico and year-round workers could remain in the U.S. three years, and then they would have to stay in Mexico at least one year before returning legally. U.S. employers and guest workers would pay social security taxes to a trust fund that would reimburse U.S. hospitals that provided emergency medical care for injured guest workers; the balance of the social security taxes paid would be placed in individual IRA-type accounts that workers could receive when they surrendered their work permits to U.S. consulates in Mexico.

Gramm’s proposal covers Mexicans employed in all U.S. industries, but does not include a path to immigrant status. The other extreme is legalization. Under a plan embraced by the AFL-CIO and many church and ethnic groups, unauthorized foreigners in the U.S. from any country, and employed in any industry, could become immigrants, and then sponsor their families for admission. Rep. Luis V. Gutierrez introduced a bill that would grant immigrant status to all persons who were in the U.S. at least five years, and temporary legal status to those in the U.S. less than five years. When unauthorized foreigners reach the five-year U.S. residence mark, they could apply to convert their temporary status to an immigrant status.Only unauthorized foreigners who have worked in the U.S. would be eligible, and they must continue working to maintain their temporary legal status and to eventually become immigrants. Earned legalization appeals to those who associate immigration with work in the U.S., and allows Mexican President Fox to keep his promise of improving conditions for the migrants he calls “heroes” for working in the U.S. and sending remittances to Mexico. A spokesperson said President Bush supports “a new temporary-worker program that would allow for some of the [unauthorized] workers to achieve permanent residency status over a period of time.” In 2003, it appears that Democrats, unions and immigrant rights groups will settle for earned legalization, but they oppose new temporary worker programs, while Republicans and most employers favor new temporary worker programs, but oppose an easy transition to legal immigrant status.Many human activities have had a significant effect on the environments in which they take place, and agriculture is no exception. California’s natural waterways have been greatly modified to enable conveyance of water to its farmlands as well as its cities, and to provide facilities for flood control, navigation, and hydroelectric power generation. Most of the natural wetlands in the state have been drained and transformed into fertile, highly productive agricultural land. Farmers have introduced many new species of plants and animals to California and in the process changed many of its ecosystems. While modifications of California’s environment have generated immense good, they have also increasingly become a cause of concern.

Over the last half-century many policies and regulations have been introduced to control some of the effects that California agriculture has had on its environment.Two main types of policy intervention have been made. First, numerous policies have sought to control agricultural externalities. These center on issues such as reducing groundwater contamination from animal waste; worker safety, environmental contamination, and food safety problems associated with pesticide use; water-logging problems associated with excessive irrigation and lack of drainage; air pollution from agricultural waste burning such as rice, and earth mining activities; and odor pollution associated with livestock. A second set of policies has specifically attempted to preserve ecosystems and species. These policies identify and protect the environmental amenities that may be threatened or damaged by agricultural activities. Environmental policies affecting California agriculture have continually evolved over the last fifty years. The evolution has been affected by changes in technology as well as by changes in the political environment and public beliefs and preferences. For example, new knowledge about the impact of agricultural chemicals on human health and the environment, the discovery of new methods of pest control, and the introduction of new monitoring or pollution-detecting strategies have led to changes in environmental laws and regulations affecting agriculture. Similarly, changes in the relative political power of environmental groups or various farm groups and/or changes in public perception and concern about certain environmental issues have led to changes in regulations. Farming in California is subject to policy-making and regulation by a wide variety of agencies. In addition to traditional agencies in the U.S. Department of Agriculture, they include other federal agencies such as the U.S. Environmental Protection Agency and the U.S. Fish and Wildlife Service; state agencies such as the California Environmental Protection Agency, California Department of Food and Agriculture, California Department of Public Health, State Air Quality Control Board, and State Water Quality Control Board; and county and municipal agencies. These many agencies that control various aspects of California’s environment have operated under a complex set of policies that are not necessarily consistent and are subject to modification. The complexity and the changing nature of environmental policies in California have provided an ample background for research in agricultural and environmental economics. Agricultural economists have assessed the impacts of various policy proposals, attempted to provide an economic rationale for proposed policies, and introduced proposals for policy reform and modification. Some of this research may have affected the existing policies and regulations in California; some has provided general background knowledge for the body of literature in agricultural and environmental economics. A survey of the environmental policies affecting California agriculture identifies some of the difficulties that policy makers are faced with in their attempts to establish environmental regulations. Problems with detecting and monitoring agricultural pollutants have sometimes led to overly strict policing of agricultural activities that are likely to cause environmental side effects. For example,cultivo del frambueso a chemical may be banned or its use restricted even though policy makers may be concerned only with the environmental side effects of some of its residue. Similarly, animal production in a certain area may be restricted or limited even though the only local concern may be with the waste that the animals are producing. The evolution of new technologies will likely help to develop policy measures that will relate more to specific environmental side effects rather than to the general related activities . Establishment of straightforward and efficient policies is influenced by difficulties in measuring the impacts of externalities. The assessment of health risk effects and environmental side effects associated with pesticide use, for instance, is subject to much uncertainty. These uncertainties have contributed to the constant debates and controversies regarding environmental regulation affecting agriculture. One of the challenges facing the scientific community is to provide data to reduce such uncertainties. As Baumol and Oates have suggested, uncertainty regarding outcomes has led to policies that aim to reach a target level of environmental quality based mainly on biological or ecological criteria, even in instances where balancing marginal benefits with marginal costs might be more appropriate. Another practical difficulty in determining environmental quality is its multi-dimensionality. The same chemical can cause several types of environmental problems—worker safety, food safety, groundwater contamination, or damage to wildlife. The benefits of chemicals, as well as the magnitude of their environmental side effects, can vary significantly according to crop and location. The way a chemical is applied can alter its impact on the environment; a chemical sprayed from an airplane is likely to generate more environmental side effects than one applied by low-pressure, precise-application techniques. Thus the social costs associated with the use of certain chemicals may vary significantly across locations and applications, and policies such as uniform taxation or direct regulation of agricultural chemical use may be economically inefficient in many situations. Efficient regulation of the environmental side effects of agriculture may call for policies that vary by location and agricultural activity, and the need for flexibility may also provide a challenge in terms of design and implementation. Much of the economic research on the environmental regulation of agriculture has simply estimated the economic impacts of proposed regulation. However, some research has also suggested improvements in policy design and demonstrated how changes in policy instruments might result in attaining environmental objectives at much lower economic costs. This chapter discusses some of the major environmental issues arising from California agriculture, and describes the conclusions of recent economic research that has analyzed the efficacy of various approaches to handling these issues. The diversity of problems and policy issues is illustrated here through discussion of control of animal wastes, pest control and the regulation of pesticides, endangered species protection, climate change, and the growing role of agricultural land as a source of recreational amenities.California is the United States’ major dairy producer, and is home to approximately one-sixth of the nation’s dairy cow population. These 1.64 million cows account for over one-fifth of all milk produced in the United States . Although the United States milk cow inventory decreased by approximately 130,000 head between 1997 and 2001, the number of milk cows in California increased by 14 percent during this time. Milk production per cow has also increased by approximately five percent during the same period . In short, California dairy production has been increasing both in scale and efficiency in recent years. Until recently, the dairy industry in California had been closely concentrated near the larger population centers in Los Angeles and Northern California. The largest dairy-producing region in the state had been the Chino region near Riverside, not far from Los Angeles. These patterns were in accordance with the models of agricultural land use first developed by Johann von Thünen almost 200 years ago. Von Thünen modeled the allocation of land uses around a city as a function of the economic return, or “rent” to the land, which in turn is a function of transportation costs. In the city’s core, urban uses such as residences and industry will determine the highest value of the land. Von Thünen hypothesized that dairying and other intensive farming industries would be located immediately outside of the urban core, because they had the highest transportation costs, both in absolute terms and in terms of the losses that would be suffered by any delays in getting easily spoiled products to market. Less intensive industries such as forestry, extensive field crops, and ranching would be located further outside of the central city. The allocation of land predicted by von Thünen’s model does not take environmental externalities into account, however. Recent studies suggest that when the cost of environmental quality is taken into account, then the location of various activities have to balance transportation and pollution costs . Thus, pollution-intensive industries either have to reduce their pollution or relocate farther away from the city.

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Under the new law premium levels at higher levels of coverage have increased

The 2002 Act also created a new Conservation Security Program . This program provides annual payments to farms that use environmentally approved practices in their production operations. Because many farms here in California already apply a number of environmentally approved practices in their operations, this program would provide an additional direct subsidy to farmers on a per acre basis up to relatively small payment limits. But this program has not yet been fully implemented and is very small in total funding.Based on recent data, the Federal Crop Insurance Program provided about $37 billion in protection on about 78 percent of the nation’s insurable acres in 2001 . The crop insurance program has experienced rising participation during the past decade as subsidies have increased and coverage has been extended to more crops. The 2001 level was nearly three times as high as the level in 1990, when crop insurance guarantees amounted to about $13 billion. This protection cost taxpayers about 2.8 billion in 2001. Producers paid about $1.2 billion in premiums and received about $3.1 billion in indemnities. The Agricultural Risk Protection Act of 2000 resulted in increased premium subsidies and adjustments to the formulas used to calculate coverage.For example, the old subsidy level for a coverage level of 50/100 was 55 percent. It now amounts to 67 percent. For a higher coverage level of 75/100, the subsidy level increased from 24percent to 55 percent. This change produced significant cost savings for producers purchasing revenue insurance compared to previous years and also led to a higher number of producers choosing a higher level of coverage. This policy reform has the effect that the crop insurance plays a more important role in the present PSE calculations than it has done under past calculations, because more producers are likely to participate in the program due to the lower cost . On a nationwide basis, the 2000 Act invests an additional $8.2 billion over 5 years to improve federal crop insurance. With regard to California crops, the subsidy resulting from crop insurance in 2001 was substantial for cotton, all grapes, almonds, prunes, apples and wheat. Most other fruits,macetas de plastico vegetables and field crops received only little subsidy as a consequence of participating in the crop insurance program.Irrigation is a key element of the current pattern of agriculture in California.

Water subsidy to California agriculture derives from access to surface irrigation water at prices below cost and below likely market prices for irrigation water if a market were allowed. Much of the reservoir and distribution system that serves agriculture was developed by the federal and state governments. The federal Central Valley Project and the California State Water Project systems of dams and canals are important providers of water storage and delivery to growers. In these projects, water is accumulated and stored in large reservoirs in the northern part of the state and then released into the Sacramento River canals for delivery. Almost half of the water available for use in the San Joaquin Valley comes from CVP and SWP sources. In addition, the All-American Canal diverts water from the Colorado River for use in the Imperial Valley in the far south of California. Imperial Valley dependence on canal water is acute; over 90 percent of valley water comes from federal or state projects. For the PSE calculations we assembled data on irrigation water usage by crop and then developed estimates of the subsidy implicit in the CVP. Based on data from the California Department of Water Resources, we were able to obtain figures on irrigated acreage per crop and irrigation region. This enabled us to calculate the total amount of acre-foot of water applied per crop and region. These calculations are based on average irrigated crop acreage during the 1988-1998 period. For commodities without individual number in DWR data, the share is determined by value of production . The subsidy rates for irrigated water from the Central Valley Project are based on data from the Bureau of Reclamation. We calculated the subsidy rate as the difference of the contract rate that a water district pays per acre-foot and the actual cost per acrefoot. Generally, the contract rate ranges from $10 to $30 per acre-foot for most regions, but it is very low at $2 dollars per acre-foot for most contractors in the Sacramento River region. Subsidy rates varied from $10 to $40 per acre-foot depending on region. The water subsidy for California is estimated to total almost $88 million.Marketing assistance encompasses many programs and departments that provide resident assistance to the agriculture industry. Cooperative Extension and the Agricultural Cooperative Service provide advisory assistance. Inspection services are provided by the Federal Grain Inspection Service, the Food Safety Inspection Service, and the Packers and Stockyards Administration.

The state government also provided approximately $147 million for agricultural plant and animal health, pest prevention and food safety services. Outlays for the Foreign Agriculture Service, Agricultural Marketing Service, and Office of Transportation comprise the federal portion of processing and marketing assistance. For the 1999-2001 period, the average state outlays for California Department of Food and Agriculture marketing, commodities and agricultural services totaled around $60 million. For those commodities with relatively small amounts of total support, marketing assistance provides the bulk of the support. Assessments are subtracted from outlays to determine the contribution to the PSE. Finally, there are state and federal marketing order, board and commissions for many California commodities. These are generally financed by check-off systems that apply a kind of excise tax on the marketed commodity to support promotion or research .Infrastructure support includes federal soil conservation programs, which provide assistance in reducing soil erosion and degradation of resources. While the contribution of these programs to overall support of California agriculture is small, they are included as a separate category for consistency with the PSE calculation. Economy-wide policies include taxes and federal transportation spending. There are various tax benefits for agriculture and foreign sales corporations that indirectly support the agricultural industry. Nelson, Simone and Valdes have compiled the total value of federal tax benefits to agribusiness and have also calculated the value of inland waterway construction and railroad interest rate subsidies. In general, the value of transportation subsidies is relatively small, usually around 2 percent of total support for each commodity. This is likely an over-estimate, however, because the California share in these benefits is likely smaller than the California share of agricultural output . Tax breaks were a larger share of the support, but were not substantial by themselves. We did not include in our PSE calculations the value of state and local real estate tax benefits to agriculture. California, like many other states in the United States, provides for a special taxation rate on agricultural real estate. The state’s Williamson Act, introduced in 1965,macetas rectangulares provides a preferential assessment program for agricultural land. Williamson Act acreage currently represents almost half of California agricultural land. Under the Williamson Act, landowners sign a contract with the appropriate local government agency restricting urban use of that land for ten years.

In return, property under Williamson Act protection is assessed for tax purposes according to its capitalized agricultural income. Capitalized income assessments are usually about half of the market value-based assessments for Williamson Act land; thus landowners receive approximately $120 million in tax benefits. Contracts may be terminated through non-renewal or cancellation. Non-renewal gradually phases in the market value-based assessment over nine years; at the end of the ten-year contract, the land is appraised at full market value. Cancellation of Williamson Act contracts must be approved by the local governing board after conducting public hearings. If the contract cancellation is approved, the landowner pays a penalty of 12.5 percent of the current market value of the land .Dairy policy is discussed in detail above. Here we note only that, in addition to trade protection and internal price policies, the dairy industry receives support from several smaller programs as well. In addition, the dairy industry receives indirect support in the form of subsidies to the grain industry and, especially, the alfalfa hay industry. Hay is important in dairy production, accounting for about 20 percent of total costs. The major subsidy for alfalfa is irrigation water; some have argued that the water subsidy to alfalfa is a major contributor to lower dairy production costs in California. Let’s examine this proposition. Total alfalfa support is about $34 million. Most of this, about $15 million is attributable to the irrigation water subsidy. Some of the alfalfa and other hay grown in the state is consumed by other livestock. Approximately $12 million of the water subsidy to hay is ultimately of benefit to the dairy industry. If the $12 million were added to a subsidy of about one billion dollars, it would raise the overall dairy subsidy from 33.4 percent to 33.6 percent. In other words the effect of irrigation subsidy on dairy is very small, especially compared to the subsidy from other sources.Commodities in this category have little government intervention in their markets. The PSEs range from about 3 to 5 percent of the revenue. There are no significant trade barriers or direct payments for these commodities. The main portion of support comes from input assistance, marketing assistance, broad government infrastructure and economy-wide policies. While these commodities have no explicit export subsidies, they do benefit from foreign market development funding to some degree, especially almonds and strawberries . Crop insurance benefits and disaster payments are also a source of a small amount of support for this group . In the citrus industry, crop insurance and disaster payments comprise almost 30 percent of the support; large payments were made following the 1990 freeze that took a heavy toll on the California citrus industry . Most commodities in this group have some sort of marketing order, either federal, state, or both. The marketing order share of total support ranges from 3 percent to around 25 percent . The share of support from research is relatively high for these commodities, around 25 percent. Nevertheless, since these percentages equal very small PSEs for the horticultural commodities, the overall subsidy is quite small.

One of the major problems in California is that the state’s water is concentrated in the north, but the majority of the state’s urban population and irrigated agriculture is located in the south. California contains 32 million acre-feet of developed water, of which 84 percent is used to irrigate 9.68 million acres of agricultural land. Because such a large proportion of water resources is used for irrigated agriculture, most water management conflicts involve the movement of water to or from irrigated agriculture. While most of the water is used to irrigate field and fodder crops, the high value vegetable and fruit crops generate the majority of agricultural revenues.From the 1950’s to 1970’s different government agencies at the State and Federal level implemented a massive water development program in California. This program was built upon the traditional supply augmentation approach to water development. Unfortunately this approach to water development is flawed. The main weakness of the traditional supply based method is that it assumes that the demand for water is perfectly inelastic and unchanging over time. An inelastic demand assumes that there is little quantitative response to changes in the price of water. Under this planning approach the quantity of water to be delivered by a water project is fixed, and the only question is how to minimize the costs of supplying it. Economic analysis is then performed to see if the total costs of the water project are less than the total benefits. Both the State Water Project and the Federal Central Valley Water Project were developed using the principles of the supply-based approach to water development. The SWP was originally projected to supply an average annual quantity of 4.2 million acre-feet of water in two stages. The first stage of 2.2 million acre-feet was built and put into service in the late 1960’s and early 1970’s. However, subsequent attempts to build the remaining 2 million acre-feet capacity have met with effective opposition from environmental interests, who want to prevent any further water development, and current contractors, who know that the average cost of water delivered by the system will have to increase by up to 300 percent to finance the completion of the planned project.