Long-term Performance of Pecan Trees when Potassium Application Is Based on Prescribed Threshold Concentrations in Leaf Tissue

Abstract

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.