Phosphorus Response in Young Pecan (Carya illinoinensis (Wangenh.) C. Koch).

Pecan phosphorus sufficiency ranges based on standard index tissue analyses typically vary, and the optimum leaf P concentrations for growth are not well defined. Phosphorus response in young pecan has rarely been documented. This study evaluated the effects of phosphorus response in young ‘Western’ and ‘Wichita’ varieties of pecan grown in San Simon, AZ. Using trunk diameter and rates of photosynthesis, transpiration, stomatal conductance, and intracellular CO₂ as proxies for positive response, and by analyzing foliar elemental concentrations of P, preliminary results suggest that ‘Wichita’ responds better than ‘Western’ to P fertilizer with respect to tree growth. Additions of phosphorus fertilizer up to 114-121 kg·ha^-1 improved tree growth; and growth increased with increasing foliar phosphorus concentrations.