Leaching of total nitrogen from nitrogen-15-labeled poultry manure and inorganic nitrogen fertilizer

Field lysimeters containing an undisturbed sandy soil mere used to evaluate leaching of manure-derived N over 3 yr. Manure labeled with N-15 (poultry excreta), which was either fresh or had been decomposed under aerobic or anaerobic conditions, was applied in May during the first year at a rate corresponding to 100 kg total N ha(-1) For comparison, labeled (NH4NO3)-N-15-N-15 (100 kg N ha(-1)) was applied simultaneously to additional lysimeters while others were left unfertilized. During the second and third year, all lysimeters, except the unfertilized ones, received unlabeled NH4NO3 at a rate of 100 kg N ha(-1). Each gear, barley (Hordeum vulgare L.) was seeded prior to fertilization. Based on the difference method, leaching of total N during the first year was not significantly different (P > 0.05) between lysimeters treated with NH4NO3, fresh manure, and anaerobic manure, but lower from those with aerobic manure. Regarding leaching of residual manure- and fertilizer-derived N estimated with the (15) method, there was a significant difference (P < 0.05) between the NH4NO3 fertilized and manured lysimeters. As much as 19, 28, and 26% leached in the treatments with fresh, anaerobically, and aerobically decomposed manure, respectively, whereas only about 3% leached in the NH4NO3 fertilized lysimeters in the two subsequent Sears. The crop uptake of labeled N were smaller in the manured lysimeters than in the NH4NO3 fertilized lysimeters. These results suggest that there is a greater potential for N leaching in the longterm from animal manures than from inorganic N fertilizers.