Relationships between Leaflet Nitrogen: Potassium Ratio and Yield of Pecan

Abstract

This study examines the relationship between foliar nitrogen:potassium (N:K) ratio and in-shell yield of pecan [Carya illinoinensis (Wangenh.) K.Koch]. Regression analysis of linear and curvilinear relationships between leaflet N:K ratio and in-shell yield identified associations relevant to orchard nutrition management. Analysis revealed that ON (heavy crop) year N:K ratio correlates with ON year yield (r2 = –0.69), OFF (light crop) year yield (r2 = +0.34), 2-year average yield (r2 = −0.52), and difference between ON and OFF year yields (r2 = –0.69) below the optimum yield level (less than 1800 kg·ha−1) for southeastern U.S. pecan orchards. Pecan yield therefore appears to be associated with N:K ratio. This study suggests that a decline in pecan yield is associated with high N:K ratios in the ON year, thus meriting further investigation into the relationships of N and K to yield. It is suggested that pecan orchards be managed such that foliage contains a N concentration of 2.5% to 2.9% and a K concentration of 1.3% to 1.5% while maintaining the N:K ratio at ≈2:1 for maximization of pecan yields in the southeastern United States over the long term.