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- Author or Editor: Ray E. Worley x
Abstract
Defoliation of pecan trees [Carya illinoensis (Wang) K. Koch] prior to October 1 prevented nutlet formation the next year in 2 out of 3 years. September defoliation was most damaging to yield, October defoliation was less damaging, and defoliation on November 1 did not reduce yield. Early defoliation delayed bud break the next year and August defoliation reduced nut size. Percentage kernel was reduced when defoliation date moved from August 1 to September 15.
Abstract
Dikegulac, when applied in the fall of a dry year, did not enhance shuck dehiscence of pecan (Carya illinoensis (Wang.) K. Koch but did promote increased numbers of new shoots on young trees the next spring.
Abstract
Leaflet mineral concentration of normal and mouse-eared leaflets differed for different cultivars of pecan (Carya illinoensis (Wang.) K. Koch). Normal ‘Schley’ leaflets were higher in Mg, Cu, Cr and Pb than mouse-eared leaflets. Normal ‘Desirable’ leaflets were lower in Cr, Pb and Cd than mouse-eared leaflets. Normal ‘Mohawk’ leaflets were higher in Mn, Cu, Al, Cr, Pb, and Cd than mouse-eared leaflets. Normal ‘Wichita’ leaflets were lower in Ca, Mg, Zn, Cr and Pb than mouseeared leaflets. Normal ‘Mohawk’ leaflets had a higher Zn/Fe ratio and normal ‘Wichita’ had a lower Zn/Fe ratio than mouse-eared leaflets.
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.
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.
After 10 years, application of 112 kg N/ha, divided into four annual applications and applied through the drip irrigation system (fertigated), provided nut yield and quality as good as 224 kg·ha–1 all broadcast or 1/2 fertigated and 1/2 broadcast. Leaf N was well above the 2.50% deficiency threshold. Treatment rates were halved for six additional years with no detrimental effects on yield and quality from fertigation. All treatments still provided leaf N well above the deficiency threshold. After 16 years of N fertigation there appears to be no serious reduction of pH or flushing of other nutrients from the wetted zone of the emitter. Leaf and soil analysis indicate a loss of Ca and Mg in the area away from the emitter when N was broadcast. Soil pH and nutrients were lower in the wetted zone of the emitter than in the area not wet by the emitter, and soil pH, K, and Mg were reduced in the 15- to 30-cm layer with fertigation. Leaf nutrient concentrations reflected the cation concentrations in the nonwetted area. Broadcast N was from NH4NO3 and fertigated N was from URAN (16% N from NH4NO3 and 16% N from urea).
Fifteen pecan (Carya illinoinensis) genotypes were evaluated over a period of 20 years in a test orchard located near Tifton, Ga. Genotypes tested included seedling selections (`Candy', `Maramec', `Melrose', `Moreland', `Sumner', and `Western Schley'), USDA releases (`Creek', `Kanza', `Kiowa', and `Pawnee'), and USDA selections (USDA 41-19-20, USDA 53-11-139, USDA 53-9-1, USDA 57-7-22, and USDA 64-11-17). Actual yields were measured for each tree in the test throughout the test period and the alternate bearing intensity (I) of each cultivar was calculated. Average annual nut production in years 1 to 10 ranged from 19 lb (8.6 kg) in the precocious cultivar `Candy' to 6 lb (2.7 kg) in the nonprecocious cultivar `Melrose'. Although a wide variation was seen in the average yield of clones in years 11 to 20, differences were not significant. A subsample of nuts was taken for each tree annually and percent kernel, nuts/lb, specific gravity, and nut volume were determined. Significant differences were found between clones for each of these traits. Most clones were not acceptable for commercial use in Georgia due to small nut size, poor kernel quality, or excessive alternate bearing. Recommended clones include: `Pawnee', which produced large nuts of excellent quality with an early harvest date, `Sumner', which produced large nuts of moderate quality with a late harvest date, and `Kiowa', a precocious bearer of large, good-quality nuts.
Yield and quality of pecan nuts were as high when 50 pounds N/acre was applied through a dripirrigation system as with 100 pounds/acre (112 kg·ha−1) applied either all broadcast or half broadcast-half fertigated. All N treatments kept leaf N well above the 2.50% (dry weight) lower threshold recommended for pecans. The 50 pounds N/acre-all-fertigated treatment resulted in less soil pH reduction and less loss of K, Ca, and Mg from soil in the nonwetted zone underneath the tree canopy than broadcast treatments. Soil pH, K, and Mg were slightly lowered in the 6- to 12-inch (15 to 30 cm) soil layer when all of the N was fertigated. Higher leaf Ca and Mg from the low rate of N fertigated reflected the higher concentrations of these elements in the soil in the nonwetted zone rather than the lower concentrations in the wetted zone. There was no evidence of a detrimental effect on the tree from lowering the N application to only 50 pounds/acre and applying it in four monthly applications through the drip irrigation system beginning 1 Apr.
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.