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Nitrogen at 112 and 224 kg·ha-1 and K at 0, 56, 112, 168, and 224 kg·ha-1 were applied to young `Desirable' pecan [Carya illinoensis (Wangenh.) C. Koch] trees to evaluate their influence on leaf scorch. Scorch severity in the orchard decreased with time even though large imbalances of N and K existed. Scorch was increased only slightly by the high N and the zero K treatments. Little scorch was observed in trees receiving K applications. Increasing K rates >56 kg·ha-1 did not reduce scorch. Correlation was not significant or very weak for leaf N, leaf K, or the leaf N: K ratio with leaf scorch in the Ray City, Ga. study, depending on the year of observation. Another study at Tifton, Ga., revealed no correlation between scorch and leaf K or the leaf N: K ratio. A very weak correlation occurred for scorch and leaf N in 1 of 2 years.
Nitrogen was applied at 112 kg·ha-1 to mature 'Stuart' pecan (Carya illinoinensis (Wangenh.) C. Koch] trees, but the radii of the application were limited to 4.6, 6.1, 7.6, or 9.1 m. Yield, nut size, percentage of kernel, tree growth, and appearance were not affected by concentrating the N application. Leaf N was highest for the largest N application radius, but all treatments supplied abundant N. Concentrating N reduced soil pH and occasionally P, K, and Ca in the 0–15 or 15–30 cm soil layers, but all three soil nutrients and Mg were medium to high after 19 years of treatments.
Soil amendments of complete fertilizer, manure and limestone added to backfill soil at transplanting did not influence pecan tree appearance or growth. Removal of ⅓ or ½ of the top at transplanting was compared with no top removal. Removal of ½ the top improved tree vigor the first year but differences in vigor and growth had dissipated by the second year. With 60 cm diameter holes, vigor and growth increased as depth increased from 30 to 90 cm. Trees planted in a 20 cm diameter post hole had poorer vigor and growth the first two years than trees planted in 60 cm diameter × 90 cm depth hole. Differences in vigor and growth due to hole size also dissipated with time and were not significant at the end of the third year. Pecan trees apparently are resilient and can overcome a poor transplanting job.
NAA was applied to pecan nuts at concentrations of 0, 20, 50, 100, 200, and 500 μg·g-1 on May 19, June 16, and July 20. The 500 μg·g-1 concentration induced nut drop at all dates but was phytotoxic to leaves when applied on May 19. Concentrations of 50-100 μg·g reduced preharvest drop of nuts.
Pecan [Carya illinoensis (Wangenh.) C. Koch] tree height was gradually reduced by removing one, two, or three limbs per year at a height <9 m. Pruning improved tree vigor and color, increased trunk circumference, terminal shoot growth, nut size, and leaf N, P, and Mg, but reduced leaf K and percentage of fancy grade kernels relative to unpruned trees. Yield was not influenced by selective limb pruning.
Abstract
Defoliation of pecan trees [Carya illinoensis (Wang) K. Koch] in August reduced yield and nut size the current season. No nutlets were set the next season when trees were defoliated on September 15 or earlier. Nutlet set increased as defoliation date became later the previous fall through November 15. Yield was less than 1 kg/tree for trees defoliated the previous season on October 15, or earlier compared with 11 kg/tree for trees defoliated November 1. Early defoliation in the fall also caused late refoliation the next spring.