Potassium was applied to old `Stuart' pecan [Carya illinoensis (Wagenh.) C. Koch] trees only when leaf concentrations dropped below thresholds of 0.25, 0.50, 0.75, or 1.00% K or annually, regardless of leaf K. Depletion of K was extremely slow, with soil K concentrations remaining at 68 to 168 kg·ha-1 (medium) or higher in the 0 to 15 and 15 to 30 cm depths after 20 years without K application. No trees were below the 0.25% leaf K threshold over the 20-year period. Yield, tree growth, nut quality, and tree appearance were similar for all K treatments. A leaf K threshold of 0.75% seemed adequate and practical for the low end of the sufficiency range.
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.
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.
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.
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.
Fall defoliation was followed by a depletion of carbohydrate (CHO) reserves and reduction or prevention of yield if defoliation occurred prior to November 1. Refoliation of August-defoliated trees restored the depleted reserves in current season’s wood tissues by December 1 but either completely prevented or greatly reduced yield the next year. September defoliation caused the greatest depletion of reserves and prevented pistillate or staminate flower production the next year. Defoliation on November 1 had no significant effect on CHO reserves.
Twenty-year-old ‘Elliott’, ‘Desirable’, and ‘Farley’ trees were pruned over, an 8-year period using: 1) pruning on only low and broken limbs, 2) removal of competing wood from alternating temporary trees, 3) top and side hedging, and 4) selective limb pruning. Wood removal from temporary trees was low, except for the last two years of the study, and little difference in yield and quality from the control was obtained. Top and side hedging reduced overall yield of ‘Desirable’ and ‘Farley’ and it changed the alternate bearing phase of ‘Elliott’ so that yields were increased and decreased in alternating years. Selective limb pruning increased yield of ‘Desirable’ in one year but, overall, gave no significant yield changes from the control. Selective limb pruning increased ‘Elliott’ yield in some years and reduced it in others to give an overall reduction in yield. Selective limb pruning did not reduce yield of ‘Farley’ significantly. Selective limb pruning usually increased nut size, and pruning effects on quality were erratic. Both hedging and selective limb pruning usually increased terminal growth. Most parameters measured showed significant cultivar × year × irrigation × pruning interactions.
Best marketable yields of tomato (Lycopersicon esculentum Mill.) were obtained when the soil pH (Tifton loamy sand) was between 6.5−6.9. Yields were reduced when soil pH was below 6.0. Liming to the desired pH increased the percentage of decaying fruit but decreased the percentage of other cull fruit. Liming increased leaf N, P, Ca, and Mg and decreased leaf Mn, Fe, and B concentrations.
Drip irrigation on 1 and 2 sides of pecan [Carya illinoensis (Wang.) Koch.] trees was programmed to irrigate when soil water suction 61 cm from the emitter was greater than 0.1 bar at either 15, 30, or 45 cm depth. Results were compared with no irrigation. The data indicate little advantage of 2 lines of emitters over one line when the same number of emitters/tree are used. The data often favored 1 line over 2 lines. Total yield of pecans was increased substantially by drip irrigation on one side (‘Desirable’ and ‘Elliott’) or both sides of the tree (‘Elliott’), but increases from ‘Farley’ were not significant. In 1968, an extremely dry year, ⅓–½ of the shucks did not dehisce completely on nonirrigated trees while 1 to 7% of the shucks did not dehisce on irrigated trees. Irrigation increased nut size. Percentage kernel was increased by irrigation in 1968 but not in other years. In 1968, percentage fancy kernels was almost doubled by irrigation for ‘Desirable’ but was reduced for ‘Elliott’.
Mature pecan, Carya illinoensis (Wang.) Koch., grove management systems of 1) rotational summer grazing, 2) clean cultivation + winter legume, 3) winter or spring intercropping + summer cultivation, and 4) closely mowed sod affected yields differently in different years, but did not affect total yield or tree growth significantly over a 10-year period. Kernel quality, nuts/kg count, nut size, and tree growth were not affected consistently by management systems. Extra fertilization, particularly N, applied to grazed and intercropped plots reduced soil pH and residual soil K; but treatments affected soil P very little. Leaf Zn and Mn were also high for these treatments. Applied N, or N from legumes, was reflected in higher leaf N. Leaf K, Mg, Fe, B, Cu, Al, Mo, and Sr were not affected significantly by management treatment.