Mineral phosphate solubilization by bacteria is often correlated with the release of organic anions and corresponding free protons, which lowers the pH in the surrounding soil water solution, and thereby induces chelation of the metal complexes Rodr g e and raga, 1999. If MPS bacterial populations are affected by biochar, this could have a significant impact on P availability from biosolid-derived biochars and plant P uptake. The abilities of the native soil bacteria to solubilize mineral phosphate in treatments prepared with biosoild-derrived biochars generated at 4 HTT’s were quantified using spectrophotometric assays and indicator media. Also, biochar could impact phytoremediation processes utilized in efforts to reduce concentrations of heavy metals and organochlorines pesticides in contaminated soils. Biochar has been shown to enhance root development in arsenic contaminated soils and influence sorption of heavy metals in soils . Some ferns have the ability to remove heavy metals from soils by translocating them into their biomass. Root development in contaminated soils can also stimulate the growth of soil microorganisms by release of root exudates that serve as substrates. Many soil microorganisms degrade organic pollutants, such as organochlorine pesticides. Also, survival of the accumulator plants is essential for successful soil remediation. In this study root-colonizing strains were isolated from soils contaminated with dichlorodiphenyltrichloroethane and arsenic and assayed for ACC deaminase activity and auxin production, microbial traits that play a major role in assisting survival of plants stressed by heavy metals . These PGPR activities were quantified across isolated cultures and mixed consortia taken from the rhizospheres of 2 fern species in contaminated soils amended with biochars prepared at 2 HTT’s. The ferns incl ded a New Zealand native species, Blechnum novaezelandiae,vertical hydroponic nft system and a species originally from China, Pteris cretica, which has been demonstrated to be an arsenic-hyperaccumulating species .
The main objective of these studies were to determine if PGPR communities were affected by different biochar materials and if this effect could be related to plant development in the given treatment soils. Changes in the expression of enzymes brought about by biochar will shed light on the physiochemical processes in the soil environment that shape the structure and function of microbial communities in the rhizosphere. Current strategies for sustainable soil management entail the use of methods that selectively enrich indigenous plant growth promoting bacteria , or carrier materials, such as biochar, that deliver beneficial soil inoculants to plant root zones. Many PGPR have the capacity to produce exogenous plant growth hormones, an activity that has been correlated with increasedtotal root length, branched root architecture, and root hair formation . Enterobacter cloacae UW5 serves as a well-studied strain for production of plant growth hormone, indole-3-acetic acid by the indole pyruvate pathway. Indole-3-pyruvate-decarboxylase is an enzyme essential for IAA generation via this pathway and the expression of the ipdC gene is induced by tryptophan . Another significant PGPR trait is the ability of some microorganisms to produce 1-aminocyclopropane-1-carboxylic acid deaminase. Under conditions of abiotic stress plants generate ethylene, which can accumulate in the rhizosphere and, in turn, elicit a stunting response in the plant, drastically reducing crop yields . Diverse soil bacteria have the enzyme ACC deaminase, which allows them to utilize the precursor to ethylene, ACC, as a nitrogen source, degrading the ACC into ammonia and α-ketobutyrate . PGPR with ACC deaminase activity have been shown to improve plant growth during flooding and drought conditions and in soils affected by salinity or heavy metals . ACC deaminase has been best studied in Pseudomonas putida UW4, and the expression of the gene encoding this enzyme is induced in the presence of ACC . The activities of each of these enzymes were determined to be essential to plant-growth-promotion by the given strains . Hence, any interference of biochar with the expression of these genes could result in loss of benefit associated with inoculum harboring these traits.
In previous work soil-microbial enzymatic activity was shown to be increased or decreased in the presence of biochar . Thus, it is important to better understand the influence of biochar on beneficial PGPR enzyme activity. Several methods were employed to analyze the expression of genes involved in ACC deaminase activity and IAA biosynthesis. Spectrophotometric assays provided initial insight into the PGPR activity of these strains as influenced by biochar in culturing media. The assays for PGPR traits among the native soil microbial communities indicated whether biochar amendment is influencing the microbial communities, possibly shaping the communities to select for more or less plant beneficial strains. For the most part, microorganisms isolated and mixed consortia cultured from the amended soils showed similar MPS bacteria proportions and activities to that of the unamended soil. However, the soils amended with BS250 had significantly lower percentages of MPS bacteria or MPS activity in mixed consortia. Of the amendment chemical properties analysed by Wang et al.the BS250 had notably higher volatile matter/ ratio and lower pH than did the other amendments. These properties may have had an influence on the soil MPS bacteria. In the case of the PGPR activities assayed in the phytoremediation study, bacteria with ACC deaminase were present in all rhizospheres and did not correlate significantly to the soil treatments. However, the W550 treatment had a positive influence on bacteria that produce IAA in the B. novae-zelandiae rhizosphere. This species of fern was found growing in the area from which the contaminated soil was extracted. The P. cretica fern species is not native to this area. Soil microbial communities may have been better adapted to the B. novae-zelandiae rhizosphere and this may exhibit a greater indication of response to biochar amendment. In other work using the same soil and biochars, microbial dehydrogense activity was significantly increased in the presence of W350 and even more so by W550 . This could indicate the benefit of using an indigenous plant species for phytoremediation of contaminated soils involving biochar.
The results of this research indicated that the biochar amendments did not affect population sizes of bacteria harboring the plant-growth promoting traits tested. During the course of this research, several PGPR strains were isolated and characterized based on PGPR activity. The use of these strains offers New Zealand organic farmers biological fertilizers composed of native species. Enzymes and their substrates could adsorb to char surfaces or be regulated by signaling molecules that interact with biochar. Recent studies generated concern over this phenomenon and showed that biochar had an effect on plant gene regulation and also interfered with microbial signaling . Figure 4.1 demonstrates that levels of indole production and ACC deaminase activity assayed from cells grown in the presence of 2% Pine600 biochar were not significantly different than those for cells grown in biochar-free medium. However,nft hydroponic system the spectrophotometric assay measures only the accumulation of these compounds in culturing medium. Hence, more sophisticated assays were developed to better monitor the expression of genes essential for these beneficial traits in aims to better resolve responses to biochar. In the in vitro gene expression studies conducted here, we did not see a biochar-induced change in the promoter activity or expression of genes involved in IAA production or ACC deaminase. The RFP reporters provided a qualitative assessment that promoter activities were positively regulated in the presence of biochar. Furthermore, the RT-qPCR provided quantitative verification that gene expression was not significantly impacted by the presence of 2% or 5% biochar. It appears that precursor compounds, such as tryptophan, were not irreversibly adsorbed to the biochars, which would have resulted in lower bacterial gene expression in the presence of biochar. This addresses the concern that biochar may interfere with PGPR activities and lower the efficacy of beneficial soil inoculants.Hunger in Africa has been central to discourses in aid organizations, NGOs, multilateral and unilateral government agencies, and billion-dollar multinational agribusiness entities for decades. Claims of concern for malnutrition on the continent are infused in initiatives for a range of issues, from economic policy to public health interventions. This phenomenon can perhaps be attributed to the visceral and immediate accessibility of the issue. The idea of hunger conjures a primal sense of urgency in the mind and hearts of donors and, as such, does not require the same degree of unpacking and validation as other equally-complex sociopolitical issues. That is, less effort is required to convey the gravity of starvation, the need to feed oneself palpable. However, that the importance of an issue is easily understood does not necessarily equate to correspondingly easy solutions. Despite this observation, many proposed hunger reduction strategies are packaged in consumable pithy slogans and oversimplified action plans, though the task requires thoughtful consideration for a number of interrelated factors, the most important of which is attaining of thorough understanding of root causes for the persistence of hunger. The continent became a more formalized “zone for agriculturalist expansion” in the last decade , as the recipient of grand gestures such as the Bill and Melinda Gates Foundation pledging to contribute 3.2 billion USD to African hunger efforts from 2006- 2011, alone .
The Bill and Melinda Gates Foundation’s Alliance for a Green Revolution in Africa as well as agrochemical company, Monsanto, feature prominently in contemporaneous campaigns that fly a banner of hunger alleviation. The surge of interest in food policy coalesced in the formation of the US-led G8 New Alliance for Food Security and Nutrition. Launched in 2012, the Alliance includes 21 African nations, 27 multinational organizations, and is fueled by corporate and AGRA donor interests. Rallying behind the premise that populations are merely undernourished because there is not enough food, the entities address caloric and nutritional deficiencies by promoting the adoption of proprietary genetically-modified and proprietary “improved” or high-yielding seed varieties, engineered to increase production of certain food staples. Thorough consideration for local nutrition ecologies, particularly ways in which trade relations can be threatened by a drastic change in agricultural output, is lacking. Thus, trials of improved and genetically-modified crops have met unsuccessful results, demonstrating that adoption of high-performing seed, alone, is insufficient. Continued implementation of failed approaches heightens risk for future populations, for it carries the potential of exacerbating the very poverty from which hunger results, while siphoning off funds that could be better used for infrastructural development and other more practical projects. Regarding GM and otherwise enhanced seed, there exists a disproportionate volume of critical research in two areas: prospective threats to environmental biodiversity and heirloom seed populations, and health risks associated with the consumption of modified foods and farm worker exposure to glyphosate. In response, multiple pro-GMO publications focus on countering those claims. Much of the research that professes the environmental and public safety of modified food crops are published by very institutions that own and produce said seed, a clear conflict of interest. Owners of the rights to proprietary seeds do not readily share their products for third party study so there is little opportunity for transparency, cross-referencing, or long term trials in controlled environments. Thus, many public health and bio-safety reports are ambiguous and inconclusive. The following paper will not directly address either of these two concerns. It is observed that proponents of Monsanto, for example, while comfortable debating human and environmental safety, fall relatively silent on the issue of financial concerns regarding the sale and use of proprietary plant species. Royalty payments and loan programs often go unmentioned, even as they threaten to burden peasant farmers or further strain government budgets. The issue of payments also implies that only certain groups will have opportunities to participate, and surplus distribution costs are not factored into foreign initiatives. Perhaps failure to address these matters is simply indicative of a failure to consider them. Or, conversely, perhaps it indicates the difficulty of providing a sound argument for proprietary seeds initiatives if evaluated strictly through the scope of financial responsibility. This paper will assess some of the glaring economic concerns related to the adoption of genetically-modified and improved seed on the continent. It will point to dilemmas which must be investigated in order for one to confidently propose the adoption of new seed varieties as a viable solution to hunger in East and Southern Africa. It will assess these matters independent of concerns related to super weeds and allergens, more narrowly focusing on implied costs, vulnerability, debt accumulation, and soft commodity trade as it relates to GM and hybrid seed adoption in Southern African Development Community member states. It is understood that undernourishment causes social problems that are antithetical to progress, but it is also true that hunger and malnutrition are the result of systemic inefficiencies.