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Trees were pruned by removing 1, 2, or 3 leader limbs per year or not pruned from 1975 through 1993. Cuts were made flush with another limb below 9 m from the ground. Pruning induced trees to respond like younger trees. Pruning increased leaf N, P, Mg, Mn, Fe, Zn, vigor, color intensity, terminal growth, nut size, and nuts per terminal. Kernel grade was reduced slightly by pruning. Yield was reduced by two or three pruning cuts per year, but not by one cut. Pruned trees were lower, more spreading, and more efficient to spray. Removal of one leader per year satisfactorily held the tree within the 21.3 × 21.3 m spacing without reducing yield. The lower height of pruned trees should decrease loss from high winds. All pruned trees survived a hurricane and a small tornado, while many unpruned trees in the area were blown down.
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.
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.
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.
Eleven `Desirable' pecan trees with yield data for 22 to 47 years were selected from a database with data from three orchards. Cumulative yield were computed for each tree. Cumulative data was transformed using LOG10. Quadratic or cubic regression curves were fit for each tree and for all in a single analysis. In most cases, variances were not homogeneous among the 11 trees. Using the regression coefficients for each tree, an average of the five was made and appropriate standard errors were computed. Number of cases where homogeneity of variances were found increased. Younger trees benefiting from better orchard management had different variances than older trees moving across changing managements. LOG10-transformation tended to decrease variation, but variances were still heterogeneous.
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.