This study evaluates the effects of nitrogen and phosphorus response in young (two- and three-year-old), non-bearing,'Western Schley' and 'Wichita' varieties of pecan (Carya illinoinensis (Wangenh.) C. Koch) grown in two orchards in San Simon, AZ. Using tree trunk diameter and rates of photosynthesis, transpiration, stomatal conductance, and transpiration as proxies for tree growth and positive response, and by analyzing foliar elemental concentrations of N and P, preliminary results suggest that 'Wichita' responds better than 'Western' to N and P fertilizer with respect to tree growth. Additions of nitrogen ranging from 5.6 kg N·ha⁻¹ to 35.9 kg N·ha⁻¹ increased foliar N concentration in 'Wichita', although there was no response to photosynthesis, stomatal conductance, intracellular CO₂, or transpiration. Additions of phosphorus fertilizer up to 112 kg·ha⁻¹ improved tree growth; and growth increased with increasing foliar P concentration.