Effect of N, P, K, and Lime on Yield, Nut Quality, Tree Growth, and Leaf Analysis of Pecan (Carya illinoensis W.)1

Abstract

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.