Nitrogen Recovery from Enhanced Efficiency Fertilizers and Urea in Intensively Managed Black Walnut (Juglans nigra) Plantations

Intensively managed forest plantations often require fertilization to maintain site fertility and improve growth yield over successive rotations. We applied urea-based “enhanced-efficiency fertilizers” (EEF) containing 0.5 atom% 15N at a rate of 224 kg N ha−1 soils under mid-rotation black walnut (Juglans nigra L.) track the fate within aboveground ecosystem components during 12-month period after application. Treatments included Agrotain Ultra (urea coated with urease inhibitor), Arborite EC water-soluble boron phosphate), Agrium ESN (polymer-coated urea), uncoated urea, an unfertilized control. increased concentrations competing vegetation one month fertilization, while neither nor urea had any effect on experiment. δ15N values in leaves crop trees above those controls two months respectively. By contrast, no until three fertilization. Fertilizer recovery (FNR) varied among components, acting as sink for nutrients. There were significant differences FNR all EEF products compared urea. was only that exhibited controlled-release activity this study, other fertilizers behaving similarly