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Warren C. Stiles

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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Warren C. Stiles

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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Warren C. Stiles

Effects of NAA at 5, 10, and 15 ppm, Accel at 50, 75, and 100 ppm, NAA at 7.5 ppm plus carbaryl at 600 ppm, and a nontreated control on fruit set, fruit size, length–diameter ratio, seed numbers per fruit, and total yield of fruit were evaluated during the 1994 season. All treatments were applied to 10-year-old `Empire'/M.9/MM.111 trees as dilute sprays at a rate of 935 liters·ha–1 with an airblast sprayer on 3 June. King fruit measured 9–11 mm in diameter at time of application. Fruit set (fruits per 100 blossom clusters) was reduced significantly by Accel at 50 ppm (17%) and by NAA plus carbaryl (26%) in comparison with the nontreated control. Total yield of fruit was increased by all treatments; however, fruit from trees treated with NAA plus carbaryl was significantly larger than that from all other treatments. Percentages of small fruit, <108 g, were reduced by all treatments. Percentage of fruit ≥ 153 g was increased significantly only by NAA plus carbaryl. Length–diameter ratios and numbers of fully developed seeds per fruit were not influenced significantly by treatments. NAA at rates of 5, 10, and 15 ppm, or Accel at 50, 75, or 100 ppm, were less effective than a combination of NAA at 7.5 ppm plus carbaryl at 600 ppm in reducing fruit set and in affecting fruit size or fruit size distribution.

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Warren C. Stiles

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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Warren C. Stiles

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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Warren C. Stiles

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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Terence L. Robinson and Warren Stiles

A field experiment was established in 1993 in a 3-year-old `Empire'/M.9 apple orchard. An incomplete factorial treatment design compared nitrogen only fertilization with nitrogen plus potassium fertilizer applied either on the ground with and without trickle irrigation or through the trickle irrigation system. Timing of potassium fertigation treatments compared season-long K fertigation to early season or late-season K fertigation. Results of main effects showed that K fertilization reduced trunk cross-sectional area increase, but increased yield, fruit size, and fruit red color. There was no benefit of fertigation compared to ground application of fertilizers plus trickle irrigation. There was no effect of source of K fertilizer (KCl vs KNO3) on tree growth, yield, fruit size, or color. Time of K fertigation showed that late-season K fertigation resulted in greater trunk cross-sectional area increase compared to early season fertigation or season-long fertigation. Fruit size was greatest when K fertigation was done in the early season. There was no effect of time of fertigation on yield or fruit red color. Potassium fertilization increased leaf K levels and reduced leaf Mg levels. Time of fertigation did not affect leaf K levels, but early season fertigation resulted in higher leaf N levels.

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Warren C Stiles and Michael Rutzke

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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Ian Merwin and Warren C. Stiles

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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Ian A. Merwin and Warren C. Stiles

This study compared various conventional and alternative orchard groundcover management systems (GMSs)—including a crownvetch “living mulch” (CNVCH), close-mowed (MWSOD) and chemically growth-regulated (GRSOD) sodgrasses, pre-emergence (NDPQT) and two widths of postemergence (GLY1.5 and GLY2.5) herbicides, hay-straw mulch (STMCH), and monthly rototillage (tilled)—during 6 years in a newly established apple (Malus domestica Borkh.) planting. Trunk cross-sectional area and fruit yield were higher in STMCH, GLY, and NDPQT, intermediate in tilled, and lower in GRSOD, MWSOD, and CNVCH treatments after 5 years. Despite N and K fertilizer applications, extractable soil N and leaf N concentrations were reduced under MWSOD and GRSOD, and soil K, P, and B concentrations were greater under STMCH. Leaf K concentrations were usually highest in STMCH trees, even when heavily cropped; leaf K declined below the sufficiency range in GLY, NDPQT, and tilled trees as they began to bear fruit. Leaf Ca was marginally deficient in all trees and was unaffected by GMS. Foliar Mn, Zn, and B concentrations declined rapidly in all treatments during 2 years without micronutrient fertilizers. Leaf Cu was higher in herbicide and tilled treatments where seasonal soil water content was intermediate (22% to 27%) and lower where soil was very wet or dry for most of the 1988 growing season. Multiple regression analysis indicated that leaf N and B and soil organic matter in 1990, and mean soil water content during the unusually dry Summer 1988, were the best predictors of fruit yield in 1990. Phytophthora root rot and meadow vole depredation were serious problems in STMCH and CNVCH trees. GMSs greatly affected tree establishment, nutrition, and yield; each system involves tradeoffs among important short- and long-term impacts on the orchard agroecosystem.