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  • Author or Editor: Warren C. Stiles x
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Zinc deficiency is prevalent in apple orchards throughout the Northeast. Zinc contained in various fungicides is partially effective in meeting zinc requirements of apple trees.

Foliar application of EDTA-zinc chelates in two or more post-bloom cover sprays are effective in supplying zinc under most conditions. Alternative materials for such applications are also being studied.

Post-harvest or pre-bloom plus post-harvest applications of alternative sources of zinc did not produce consistent improvement of growth, yield, fruit size or color, or subsequent season zinc levels in leaf samples. Application of chelated zinc through trickle irrigation systems has provided significant improvements in leaf-zinc levels and is considered to be an effective means of supplying this element.

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Studies initiated in 1986 indicated beneficial effects on growth and cropping of young apple trees from trickle irrigation plus soil application of nutrient elements or fertigation with a weekly multielement complement. In 1993, an orchard facility was established to evaluate responses to alternative sources, rates, and methods of application of K, Zn, or Cu. Results of two separate experiments with K indicate the following: 1) Application of K at 112 kg·ha-1 per year increased growth and yield of `Marshall McIntosh'/M.9 and `Royal Empire'/M.9 trees. Differences between soil surface and two fertigation regimes and between KCl and KNO3 were nonsignificant. 2) There were no differences among three sources of K (Cl-, \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} , \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{SO}_{4}^{=}\) \end{document} ) at three rates (37, 75, or 112 kg·ha-1 per year) applied in 16 weekly fertigations. All rates of K increased tree growth and yield in years 1 to 3. As cropping increased, rate effects tended to increase up to 75 kg K/ha per year. In the first 4 years, fertigation with EDTA chelates of Zn or Cu have been more effective than sulfates in increasing leaf Zn or Cu, but effects on tree growth and yield have not been significant. Results indicate no significant advantage of fertigation over conventional methods of application for K, Zn, or Cu as long as trees are irrigated adequately. E-mail wcs5@cornell.edu; phone (607) 255-1779.

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Studies initiated in 1986 indicated beneficial effects on growth and cropping of young apple trees from trickle irrigation plus soil application of nutrient elements or fertigation with a weekly multielement complement. In 1993, an orchard facility was established to evaluate responses to alternative sources, rates, and methods of application of K, Zn, or Cu. Results of two separate experiments with K indicate the following: 1) Application of K at 112 kg·ha-1 per year increased growth and yield of `Marshall McIntosh'/M.9 and `Royal Empire'/M.9 trees. Differences between soil surface and two fertigation regimes and between KCl and KNO3 were nonsignificant. 2) There were no differences among three sources of K (Cl-, NO 3 , SO 4 = ) at three rates (37, 75, or 112 kg·ha-1 per year) applied in 16 weekly fertigations. All rates of K increased tree growth and yield in years 1 to 3. As cropping increased, rate effects tended to increase up to 75 kg K/ha per year. In the first 4 years, fertigation with EDTA chelates of Zn or Cu have been more effective than sulfates in increasing leaf Zn or Cu, but effects on tree growth and yield have not been significant. Results indicate no significant advantage of fertigation over conventional methods of application for K, Zn, or Cu as long as trees are irrigated adequately. E-mail wcs5@cornell.edu; phone (607) 255-1779.

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Distribution of nutrients was evaluated in samples collected at various depths and distances from drip emitters after 8 years of application. Nutrients applied to soil surface influenced levels mainly in top 40 cm of the soil profile, while fertigation resulted in movement to depth of 80 cm within the wetted zone. NO3-N was increased in 0- to 40-cm depths by soil surface application, but below 40 cm by fertigation. Fertigation increased P in wetted zone to a 40-cm depth. Surface-applied K increased levels in the 0- to 20-cm zone, while fertigation increased K to the 80-cm depth. Zn and Cu were increased to 80 cm by fertigation. Growth and yield indicate soil surface application of fertilizers plus drip irrigation to be comparable to fertigation in most experiments. Fertigation of mature trees on M.7 with K + B for 3 years did not show consistent positive effects on fruit size or color. Responses associated with fertigation appear to be largely attributable to irrigation unless soil nutrient supplies are inadequate.

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Concerns about the impacts of agricultural practices on the environment dictate that all management techniques must be examined from the perspective of minimizing such impacts. Integrated pest management practices such as scouting, use of biological controls, improvement of pesticide application techniques, tree-row-volume spraying, and consideration of the environmental impact of alternative chemical controls offer opportunity for minimizing the adverse impact of pesticides. Improved spray equipment with canopy sensors and spray recovery systems improve deposition and reduce pesticide waste. Applying nutrients on the basis of need as indicated by leaf and soil analyses offers the best means of assuring optimal crop performance and minimizing the potential for contamination of surface and ground water supplies. Soil management practices must be evaluated for their potential to minimize soil erosion and competition, and for their potential contribution to pest management. Ground covers that are nonsupportive of nematodes, disease, or insect pest populations merit additional research. Methods for managing ground covers with low rates of growth regulators or herbicides to minimize invasion by problem weeds, reduce the need for mowing, and regulate competition, while retaining their beneficial attributes in minimizing soil erosion and maintaining soil structure, would be advantageous to orchardists and the environment.

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Nutritional status of apple (Malus domestica Borkh.) trees may influence regularity of cropping through effects of some nutrient elements at various stages of the floral initiation, development, pollination, fertilization and fruit setting process. Other elements may influence regularity of cropping more indirectly as consequences of their effects on physiological processes or by modifying the sensitivity of the tree to adverse environmental factors. This report provides a brief summary of reported impacts of mineral nutrition on regularity of cropping.

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Potassium nitrate, potassium sulfate and potassium acetate were applied as foliar sprays at recommended rates for each material to Empire and McIntosh apple trees in a potassium deficient orchard. Five sprays of each material were applied at approximately one-week intervals beginning in mid-August All sprays were applied by means of a small air-blast sprayer calibrated to deliver 800 1 ha-1 of a 1.744X tank mix, i.e. equivalent to dilute sprays of 1400 1 ha-1. Total amounts of K applied per ha were 8.6 kg with K-acetate and 28 kg ha-1 with K-nitrate and K-sulfate. Leaf samples were collected from each plot at normal harvest date for each variety and washed prior to drying and analysis. Regression analysis indicated a significant (P=0.05) positive relationship, r = +0.4740, between total amount of K applied and leaf K regardless of the source. Significant positive relationships were found between average fruit weight and percent leaf potassium with both varieties.

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A total of 3850 leaf samples from commercial apple orchards located throughout New York State were submitted for analysis during the 1989-1992 seasons. These included 2583 samples from mature, 968 from young bearing age, and 299 from young nonbearing orchards. Percentages of samples (all ages and all varieties combined) found to be below currently recommended levels were: Zn 75%, Cu 74%, B 68%, Ca 63%, K 60%, Mg 60%, Mn 38%, Fe 19%, N 15%, and P 8%. Percentages of samples found to be above currently recommended levels were: N 21%: Zn 16%, Mn 13%, K 6%, B 4%, Mg 2%, Cu <1 %, and P <l %. Major problems consist of shortages of Zn, Cu, B, Ca, K, and Mg in 60% or more of all samples analyzed. Seasonal, varietal, pest management program, and tree age effects were apparent in the results, indicating that these factors must be considered in interpreting results of leaf sample analyses into recommendations for fertilization programs.

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A field experiment was established in 1992 with `Empire' apple trees on either M.7 or M.9 rootstock. Preplant fertilization with NPKB plus lime compared to the lime only control did not increase tree growth during the first 4 years, but did increase cumulative yield (10%) and average fruit size (7%). The addition of annual applications of ground-applied NKB after planting increased total shoot growth 17%, as well as yield (26%) and fruit size (14%) compared to the lime only control. Trickle irrigation significantly increased trunk cross-sectional area (17%), shoot growth (16%), yield (18%), fruit size (5%), and yield efficiency (7%). The interaction of ground fertilization and trickle irrigation showed that trickle irrigation increased the benefits of ground applied fertilizers. Without trickle irrigation, ground-applied fertilizers increased shoot growth only 6% and yield 14% compared to the unfertilized controls, but, with the addition of trickle irrigation, the ground-applied fertilizers increased shoot growth 21% and yield 21% over the irrigated but unfertilized control. Ground fertilization increased yield efficiency and fruit size by the percentage by whether or not trickle irrigation was present. Fertigation gave similar results as the trickle plus ground fertilizer treatment on tree growth, yield, fruit size, and yield efficiency. Our results indicate that trickle irrigation in the eastern United States can improve tree growth, yield, and fruit size in the first few years after planting. The addition of ground-applied fertilizer or fertigation can improve tree performance even more. However, in the humid New York climate, there does not appear to be a significant benefit from injecting the fertilizer into the trickle water compared to applying the fertilizer on the ground.

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Eight vegetation management systems (VMS) were evaluated over four years in a newly planted apple site. VMS treatments included pre- and post-emergence herbicide strips, a close-mowed sodgrass, a growth-suppressed (maleic-hydrazide) sodgrass, a crownvetch “living mulch,” clean cultivation, and straw mulch. Soil moisture supply was highest under the straw mulch and lowest under crownvetch, and varied inversely with groundcover biomass. Leaf N was deficient in tress in both sodgrass VMS, and increased by the lequme “living mulch” only after four years. Leaf Cu was lowest, and appeared to limit tree growth in VMS with prolonged soil moisture deficits. No significant differences were observed in leaf transpiration over a broad range (10 to 700 kPa) of soil matric tension. Cumulative trunk crosssectional area was greatest in straw-mulched trees and least in sodgrass and crownvetch VMS. The optimal soil matric tension for nutrient uptake and tree growth appeared to be 175 to 200 kPa in this orchard. Increasing the width of glyphosate herbicide strips from 1.5 to 2.5 m in tree rows did not improve tree growth, nutritional status or fruit yield.

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