Search Results
A threshold of 2.75% N was most practical for the low end of the sufficiency range when lower thresholds of 2.25%, 2.50%, 2.75%, and 3.00% were tested on old `Stuart' pecan [Carya illinoensis (Wangenh.) C. Koch] trees. Application of 224 kg N/ha annually reduced nut size when compared with application of 112 kg/ha made only when leaf N dropped below 2.25%, 2.50%, 2.75%, or 3.00%. Yield and tree growth were similar when 112 kg·ha-1 was applied only when leaf N dropped below 2.75% and when 224 kg·ha-1 was applied annually. No N application was necessary to meet the 2.75% threshold for 3 of the 16 years.
Abstract
Mature ‘Stuart’ pecan trees in good condition on Tifton loamy sand did not respond to fertilizer [10-4.4-8.3 (N-P-K)] at rates from 0-1344 kg/ha annually over a 10-year period, but color and vigor of trees receiving no fertilizer were reduced near the end of the study. Highest yields were obtained with 448 kg/ha. Fertilizer effects on shoot growth and nut quality were inconsistent, but quality tended to be poorer for heavily fertilized than lightly fertilized trees near the end of the study. Fertilizer and limestone effects on yield and shoot growth were also inconsistent for mature ‘Stuart’ trees on Leefield sand at Way cross, Ga. over a 10-year period. Leaf analysis responded very slowly to nutrient application with leaf N and K being first increased by fertilizer application in the 6th and 9th years, respectively. Fertilizer P had little effect on leaf P. Liming to pH 60 with calcite increased leaf Ca and decreased leaf Mg and Al.
Yield and shoot growth of young ‘Desirable’ trees increased with the first 56 kg/ha increment of N, but further increases due to the second increment were seldom significant. Phosphorus and K additions had little effect on yield and shoot growth, but increasing K reduced nut size. Increasing N rates to 112 kg/ha improved vigor and color of trees. Leaf N and K for young trees increased from increasing application levels the first year, and leaf K was maintained in the desired range when soil test plus applied K equaled 112 kg/ha annually. Increasing N and K applications reduced leaf Mg, and increasing K applications increased leaf Mn, Fe, Al, and Na in young trees.
Abstract
Fentin hydroxide and benomyl increased nutlet set in 1969 but not in 1970. Fungicide sprays had little effect on starch content of wood tissue in late March of the year following application. Starch and sugar content of 6 wood tissues in March and nutlet set was not associated with leaf scorch index the previous fall. Starch content of wood tissues in late March ranked as follows from greatest to least: Roots > 2.5 cm diam, trunk, scaffold limbs, new wood, 1-year-old wood, and roots < 1.3 cm diam. Soluble sugar content ranked: Roots < 1.3 cm diam, 1-year-old wood, new wood, roots > 2.5 cm diam, trunk, and scaffold limbs.
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.
Interfering limbs of alternating (temporary) `Elliott' pecan trees were pruned annually to provide growth for limbs of permanent trees for a 6-year period. Yield, nut quality, and tree growth were similar for pruned and nonpruned plots, but there were year × pruning interactions. Yields of the permanent trees were not affected by pruning the adjacent temporary tree.
The Coastal Plain Experiment Station has been evaluating pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars for over 75 years. Using annual yield data from this program, the alternate bearing intensities (I) of 66 pecan cultivars and numbered U.S. Dept. of Agriculture (USDA) selections were determined. Values ranged from 0.19 to 0.93 in young trees, and from 0.27 to 0.91 in mature trees under high-input production practices. The adoption of fungicides, insecticides, and irrigation during the last 30 years has reduced the average I value from 0.70 to 0.55. I was negatively correlated with both nut yield and nut weight. All but one cultivar recommended for commercial production in Georgia have I values lower than the average of 0.57 for all cultivars in this test. Values calculated early in a tree's productive life cycle were highly correlated with those of mature trees.
Pecan [Carya illinoinensis (Wangenh.) C. Koch] tree height was gradually reduced by removing one to three limbs per year at a height <12 or <9 m or none. Pruning at either height reduced yield but increased tree vigor, terminal shoot growth, nut size, and percentage of “standard” grade kernels. Pruning reduced leaf Mg and percentage of “fancy” grade kernels.
Abstract
Fungicidal applications in 1966 exerted a profound influence on the number of nutlets set in 1967. Nutlet set ranged from practically none without fungicide sprays to 1.34 per terminal where 5 applications of Du-Ter were made at the rate of 0.12 lb per tree. Du-Ter was the most effective fungicide and dodine was next best in their enhancement of nutlet production. Dodine and Du-Ter were also most effective in controlling scab.
Treatments of control, selective limb pruning (SLP), tree thinning, SLP + 12.24 kg paclobutrazol/ha, and SLP + 3.36 kg paclobutrazol/ha were applied to `Desirable', `Western Schley', and `Wichita' pecans for >7 years. Thinning increased yield per tree significantly for `Desirable' but not for the other cultivars. Thinning did not increase yield per hectare during the study. Paclobutrazol application reduced terminal shoot growth but did not benefit yield or kernel quality. There was no significant benefit from SLP with or without paclobutrazol.
Abstract
A quick method of estimating pecan yield is described and compared with mechanically harvested yields. The estimate accounted for 80% of the yield variation.