Fertilizer Uptake, Partitioning, and Recovery in Container- Grown Common Hackberry (Celtis occidentalis) Trees

Ammonium-nitrate (NH4NO3) double enriched with the 15N isotope (1.5 atom %) was used to evaluate fertilizer N recovery, N partitioning, and aboveground N status in container-grown common hackberry (Celtis occidentalis L.) trees back-filled with native soil at Arlington, Wisconsin and Lisle, Illinois, U.S. Treatments consisted of 0, 1.42 g N tree-1 (0.05 oz) and 4.27 g N tree-1 (0.15 oz), the area equivalent of 0, 0.49, and 1.47 kg N 100 m-2 (0, 1, and 3 lb N 1000 ft-2). Trees were harvested 14, 30, 60, and 90 days after fertilization. Fertilizer-induced changes in aboveground N status were significant only at the 4.27 g N tree-1 (0.15 oz) treatment level. The amount of fertilizer N recovered in aboveground tissues increased with rate of application. Fertilizer N was preferentially partitioned to foliage and current season stem wood. The percentage of fertilizer recovered in aboveground tissues did not differ between the application rates, ranging from 15%–25% at Arlington, WI, and 5%–9% at Lisle, IL. Frost damage to the foliage at Lisle, IL may have resulted in location differences in aboveground biomass which affected fertilizer N uptake and recovery. These data suggest fertilizer N accumulated in nontarget sinks and/or were lost from the site of application at both rates of application.