Submitted to: HortTechnology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/23/2007
Publication Date: 10/1/2007
Citation: Wood, B.W., Well, L. 2007. Relationship between leaflet nitrogen: Potassium ratio and yield of pecan. HortTechnology. 17(4):473-479. Interpretive Summary: Interpretive Summary: The high and rising cost of nitrogen (N) and potassium (K) fertilizers means that optimization of these key nutrient element is increasingly important to commercial orchard enterprises. The relative leaf concentrations of these elements are important, but the relative ratio of these elements is also important for optimization of orchard productivity. Research evaluating tree yield characteristics against various N:K ratios found that yield was optimum at a ratio of approximately 2.1 and that higher ratios were detrimental to nut yield. This information enables pecan farmers to avoid wastage of money on excessive N fertilizer applications and increases the probability of improving orchard productivity and profitability.
Technical Abstract: This study examines the relationship between foliar N:K ratio and nutmeat yield of ‘Desirable’ [Carya illinoinensis (Wangenh) K. Koch] pecan. Regression analysis of linear and curvilinear relationships between leaflet N:K ratio and in-shell yield identified associations relevant to orchard nutrition management. Dependent variables included two-year average in-shell yield, difference in in-shell yield between ON and OFF years, ON year yield, and OFF year yield. Independent variables included the two-year average N:K ratio, the difference between ON year N:K ratio and OFF year N:K ratio, ON year N:K ratio, and OFF year N:K ratio. Analysis revealed that ON year N:K ratio correlates with ON year yield (r = -0.69), OFF year yield (r = +0.34), two-year average yield (r = -0.52), and difference between ON and OFF year yields (r = -0.69) below the optimum yield level (<1800 kg'ha-1 ) for ‘Desirable’. Orchard nutmeat yields of ‘Desirable’ therefore appear to be influenced by N:K ratio and appear substantially reduced by high N:K ratios; thus meriting further investigation into the relationship of N and K to yield. It is suggested that pecan orchards be managed such that foliage contains a N concentration of 2.5-2.9% and a K concentration of 1.3-1.5%, while maintaining the N:K ratio at approx. 2:1 for maximization of nutmeat yields over the long-term.