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Chloride and boron toxicity symptoms and tissue concentrations were characterized and distinguished in kiwifruit. Dormant cane, bud, emerging leaves, blade and petiole samples were taken from February through October 1989 from three vineyards - a high chloride, a high boron and a low boron, low chloride control. Chloride toxicity symptoms started showing in early summer on basal leaves. By late summer, necrosis symptoms were on mid-shoot and leaves near the shoot terminal. In boron toxicity, interveinal chlorotic areas appeared first followed by marginal necrosis. Symptoms were seen on basal leaves in early spring, progressively affecting upper leaves by harvest. The high chloride vineyard accumulated chloride from early spring with the petiole concentrating more chloride than the blade. In the high boron vineyard, boron increased greatly in the blade but not in the petiole. Another sampling procedure other than mid-season leaf samples could be emerging leaves for detecting high chloride and dormant cane tips, buds or emerging leaves for high boron.
In a comparison of six walnut rootstocks either nursery-grafted or field-grafted to `Chandler' (Juglans regia), the highest-yielding trees after 9 years are on either seedling or clonal Paradox rootstocks. Trees growing on both Paradox rootstocks had higher yield efficiency than trees on the black rootstocks in both 1995 and 1996. Since 1993, relative tree size based on trunk circumference has not changed: southern California black (J. californica), seedling Paradox and northern California black (J. Hindsii) have remained significantly larger than clonal Paradox, Texas (J. microcarpa) or Arizona (J. major) black rootstocks. The smaller size of clonal as compared with seedling Paradox trees might be explained by a delay in field grafting success. Although both northern and southern California black rootstock trees were significantly larger than clonal Paradox trees, they did not differ significantly in yield and had significantly lower yield efficiency in 1996. Clonal Paradox trees have significantly smaller nut size than northern California black rootstock trees that can be explained by its higher yield efficiency. An adjacent trial planted in 1991 compares micropropagated `Chandler' on its own root vs. `Chandler' on seedling Paradox rootstock. In 1995 and 1996, own-rooted `Chandler' had significantly greater trunk circumference, yield, and yield efficiency than did `Chandler' on Paradox rootstock. Many of the trees on Paradox rootstock are growing very poorly compared to the own rooted trees. This could be due to diversity within the Paradox seed source. If own-rooted `Chandler' trees become commercially available, they may have potential in areas where other rootstocks are undesirable because of hypersensitivity to cherry leafroll virus.
A kiwifruit vineyard converted to an organic farm was compared to a conventionally farmed vineyard from 1990 through 1992. February or March applications of composted chicken manure (organic plot) or NH4N O3 plus CaNH4 (NO3)3 through microsprinklers during the growing season (conventional plot) were applied to give equal rates of N. Soil analyses indicated no differences in nutrient or salt levels. Nitrogen leaf levels from the organic plot were consistently lower than those from the conventional system but were not deficient. Leaf concentrations of sodium and chloride increased over the three-year period in the organic plot, but not to phytotoxic levels. Organically grown fruit was as firm or firmer than conventionally grown fruit at harvest and four months after harvest. Damage from latania scale or omnivorous leaf roller was minimal in both plots until 1992, when the organic plot had 3.9% scale compared to 0% in the conventional plot. An economic analysis comparing the short-term profitability of the two systems will be presented.
In 1994, we established that a surfactant, Armothin (AR), reduced fruit set when applied as 3% and 5% AR at 100 gal/acre with a Stihl mistblower to `Loadel' clingstone peach [Prunus persica (L.) Batsch]. In 1995 we compared 3% AR at volumes of 100 and 200 gal/acre (935 and 1870 L.ha-1, the volumes most commonly used by tree fruit growers in California) applied with commercial airblast sprayer; overthinning resulted with the latter. In 1996, we applied 3% AR at 100 gal/acre and 1% AR at 200 gal/acre. In 1995, differential applications of 3% AR at 100 gal/acre (two-thirds of the material applied to either the upper or lower canopy) reduced fruit set in the upper canopy in proportion to the amount of chemical applied (twice as much fruit set reduction with twice as much chemical); fruit set in the lower canopy was reduced by an equal amount regardless of amount of chemical used. Salable yields, equivalent to those obtained by hand thinning, and improved fruit size were achieved with all treatments of 3% AR at 100 gal/acre in 1995 with a 76% reduction in hand thinning. Following a low-chill winter (1995-96) with a protracted bloom, flower bud density (return bloom) was significantly greater in 1995 AR-treated trees. In 1996, treatment with AR did not result in fruit set reduction due to the protracted bloom and poor weather conditions before and after bloom. Nonetheless, 1% AR at 200 gal/acre applied in 1996 increased salable yield and increased final fruit mass. Return bloom in 1997 was equal among 1996 treatments.