Data from this trial had a similar trend for the relationship between light interception and yield. In the June Flame cultivar, yield measurements up to 50% light interception had little deviation from the linear model, above this point yield varied significantly. Above 50% light interception, differences in yield are likely caused by other limiting factors such as water or nutrients . This would also explain the poor fit for the model of the C-6 V system. With a canopy that intercepted >50% in all three seasons, yield variation was likely a result of environmental conditions. August Flame systems had more time in the first growing season to fill out their allotted space. This resulted in most systems having >50% light interception in all three seasons. Due to the higher light interception, all models had a poor fit and did not provide confident yield predictions.There were often significantly higher fruit counts and larger fruit compared to the Nema Quad system. In the June Flame 2019 harvest data there was a significant difference detected in slopes comparing fruit size vs fruit per hectare however the difference was related to the C-6 Quad system having the best fit to the model for that season. Overall, this system proved capable of producing yields on par with the current commercial systems. The C-6 V system also proved to be a successful alternative to the current standard systems. Fruit sizes and crop loads matched the Nema Quad system in most seasons. High-density plantings may be more suitable for late-bearing cultivars and growers attempting to reach harvest a season earlier may find it difficult to do so with high-density plantings and an early-bearing cultivar. One drawback is the number of trees that must be managed in this kind of a system. With almost 1800 trees per hectare,macetas de plastico initial costs are higher than a planting with half as many or fewer trees. The C-9 Quad system performed poorly compared to all other systems.
These results would suggest that the system is not capable of matching commercial production. However, systems using the C-9 root stock and higher density plantings have been reported to be more productive than data from this trial suggest. With contrasting results from previous studies, nothing conclusive can be proposed. The Nema Quad system did well as a representation of current commercial standards. The strong benchmark provided by this system highlights the impressive productivity of the C-6 V and C-6 Quad systems. Fossil evidence indicates Olive trees originated 20-40 million years ago in the Oligocene, in what is now the eastern Mediterranean Basin . The olive plant was first cultivated ~ 7000 years ago in the Mediterranean basin . Olives are not native to the Americas. Spanish colonists introduced olive cultivation in present day Peru, Chile, and Argentina in 1500s . The Spanish missionaries brought the olives to California in 1700s . Around 1870, several small orchards with many different European varieties were cultivated for oil along the California coast, from San Diego to Sonoma, and in some foothill areas of the Sierra Nevada Mountains. By 1885, there were 2,000 acres of oil olives planted in California. However, this olive oil industry was not competitive against seed oils or European olive oil imports. The “California Style Black Ripe” olive was developed in the early 1900s, and the California industry focused on table olives, increasing to 35,000 acres by the 1980s . However, in the last four decades, the California table olive industry has declined. Stagnant grower prices, high hand-harvest costs and strong international competition with lower-priced imports have decreased the California table olive industry to 15,500 acres in 2020 . During the same period, the olive oil industry increased to 20,000 acres . This rapid reestablishment of a California olive oil industry was greatly facilitated by cultivars bred to remain small, grow in intensive hedgerow orchards, crop early, and be mechanically pruned and harvested . For the past two decades, olive oil has been promoted as a healthier alternative to other fats and oils.
American olive oil sales have increased 100% from 1991 to 2003 and continue to grow. The US ranks as fourth in world olive oil consumption . This increase in olive oil consumption drove the California olive oil industry to increase domestic production, from 247,500 gallons in 1999-2000 to nearly 400,000 gallons in 2004-2005. Currently, most oil olive orchards are in San Joaquin and Sacramento valleys . Average yields for the past decade have ranged from one to six tons per acre of fresh fruit . However, while consumption is increasing and markets are strong, producers struggle to produce the 5 tons per acre and 190 to 210 gallons of oil per acre needed for economic sustainability. The genus Olea in the family Oleaceae has about 35 species, but Olea Europaea L. is the only one that produces edible fruits. Cultivated olives are medium-size evergreen trees that reach ~ four to eight meters tall. They have dense foliage and bear fruits on the previous year’s apical shoot growth. The simple, lanceolate leaves live for two to three years. The petioles are short, with each node composed of two opposite leaves. The fruit is borne on clusters in the axils of the opposing leaves . Olives grow best in Mediterranean climates with mild winters and warm, dry summers. They are cultivated primarily within the 30° to 45° north and south latitudes. Olives are cold sensitive. When actively growing, temperatures below 0°C damage shoots and kill buds. Temperatures slightly above 0°C decrease bloom. An annual mean absolute minimum temperature below -7°C demarcates the geographical range for olive production . Most cultivars require winter chill of ~ 400 hours below 7°C to break dormancy and bloom. Olives are most sensitive to low and high temperatures during bloom. Flowering can be delayed at low temperatures , and high temperatures can limit pollination and pollen tube growth . The optimal temperature for olive pollen germination and pollen tube growth is 20 to 25°C . Sufficient heat accumulation during the growing season is needed for successful fruit maturation. Full fruit development in olives required 1,225 Celsius degree days . When mature, olives are strongly apically dominant with axillary inflorescences borne on the previous year’s shoot growth. Inflorescences form during the previous season on the growing-shoot leaf axils .
The buds are induced in early summer, initiated in the late fall, and differentiate after dormancy into perfect or imperfect flowers. . Their reproductive or vegetative fate will be determined from mid-June to late October. The process of flower bud formation is called floral induction. The presence of fruit on one-year-old shoots inhabits floral induction on the current year’s shoot growth. Thinning an olive tree within six to seven weeks of flowering increases flowering during the following year . The destruction of seeds of very young fruit without destroying the pericarp flowers can also increase the subsequent year’s flowering . Gibberellins, synthesized in the seeds of a developing fruit, were an important inhibitor of floral induction . Olive inflorescences are 1.5 to 4.0 cm long, with 10 to 35 flowers . The inflorescences have a paniculate structure: flowers grow on the central axis and sometimes sub-branching or secondary bearing-axes can occur . Olive flowers are actinomorphic , and the corollas are composed of four white or yellowish white petals .Olive has an andromonoecious reproductive system,macetas rectangulares producing perfect and male flowers on an individual tree . The imperfect male flower has two stamens, with relatively big, bright yellow anthers and short filaments . In perfect olive flowers, the female reproductive system is a pistil with bi-lobed stigma, a short white style, and a green round ovary . The ovary has two locules or cavities, and within each are two ovules. Fruit development requires fertilization of one of the four ovules . The factors that affect the proportion of perfect flowers include substrate competition, cultivar, and environmental conditions . In a normal year. About 50% of flowers are pistillate .Pollination and fertilization are required for fruit production. During pollination, a pollen grain lands on the stigma and germinates, producing a pollen tube, which grows through the stigmatic surface and down the style to the ovary . Ovules of olives are anatropous and during development, they orient so that the micropyle faces upwards . Like many other angiosperms, after successful pollination, one of the two olive male gametes fuses with the egg cell to become the diploid embryo. The other male gamete unites with two polar nuclei to become the triploid endosperm . Only one of the four ovules isfertilized and develops into a fruit. Vascular bundles separate the future endocarp and mesocarp . Botanically, an olive fruit is a drupe. The mesocarp is the fleshy part of the olive and the endocarp is the stony shell that encloses the fertilized embryo. Some argue olives are allogamous, meaning they require, or produce better, with crosspollination. However, they may self-pollinate but often display self-incompatibility, particularly if temperatures are high during bloom . Olive self-incompatibility is attributed to the slow growth of the pollen tubes of the same cultivar through the stigma, resulting in arrival after the ovule has degenerated . However, no failures in fruit set were detected in cross-pollinated Spanish olive groves, so the delay in self-pollinating cultivars might not be the reason for fruit set failure . Mass abscission of young fruit and unfertilized ovaries are a result of competition for assimilates. In the ‘Gordal Sevillana’, cross pollination reduces the number of shot berries and parthenocarpic fruit with little commercial value.
In the ‘Manzanilla de Sevilla’, cross-pollination increases fruit set. However, in other varieties such as the ‘Arbequina’, there is very little difference in the fruit set in response to cross-pollination . A mature olive tree produces abundant flowers, but only a small portion of them persist as fruits . Anthesis of olives lasted seven weeks, starting at bud break . Most inflorescence axis elongation happens during the third week after BB, massive bract shedding occurs the fourth week after BB, and full bloom occurs seven weeks after BB. Intense abscission of flowers and fruits happens five to seven weeks after FB . During the intense abscission period, imperfect flowers abscise before the perfect flowers and fruits, with overlap . Olive yield depends on the population of viable pistillate flowers, their pollination, fertilization, and persistence as fruits . The number of inflorescences affects final fruit set and the number of fruits within one inflorescence is consistent between years and within cultivars . The final olive fruit set correlates positively with the quantity of pollen during bloom . Ovule longevity is fundamental to flower pollination and fertilization in apples, leading the concept of an Effective Pollination Period . EPP is determined by the longevity of the ovules minus the time required for a pollen tube to grow to the ovule. Longer ovule persistence or viability could increase the EPP and, therefore, potentially fruit set in olives .Olive, like apple, pear, mango, and other fruit trees, are alternate bearing, meaning they produce alternating large and small crops . Alternate bearing does not cause harm to trees , but it destabilizes management, production, and marketing . One hypothesis is that carbohydrate depletion during an “on” year due to fruit growth causes low fruit set in the subsequent “off” year . Olive trees placed in growth chambers under favorable conditions for growth: light, temperature, and high CO2 concentration, had five times more non-structural carbohydrate accumulation than controls . However, the olive trees in the chamber still failed to bloom or set fruit successfully. This observation suggested that the lack of photosynthates was not the primary reason for alternative bearing. The developing fruit is an inhibiting factor for floral induction in olive. Reducing the crop load six to seven weeks after flowering resulted in increased flowering for the following year . Olive fruit seed development is a strong influence on inflorescence development . When olive fruit seeds were killed within six weeks after full bloom, leaving the bearing shoots with seedless fruits, the current year’s shoot growth produced more inflorescences the following year than branches with seeded fruits. Gibberellins, synthesized in seeds of developing fruits, were an important inhibitor of floral induction .