Denitrification associated N loss in mangrove soil

Abstract

Despite the well-known mechanism of N loss through denitrification in wetland, little information is available for mangrove soil. The aim of this study is to quantify N loss via denitrification in mangrove soil, to clarify factors affecting denitrification and to evaluate the role of plants in the mechanism of nitrification–denitrification in mangrove soil. The N loss from mangrove soil was 76%, possibly 55% through denitrification, measured using a 15N tracer technique. The N loss was reduced to 45% when a nitrification inhibitor, N-serve, was added. Planting reduced the N loss from mangrove soil more than the nitrification inhibitor. The combination of planting and applicasion of nitrification inhibitor completely prevented N loss from mangrove soil. Denitrification in fresh soil samples from a mangrove forest declined markedly from the surface to the sub-surface soil. Available C limited denitrification. The ability of glucose to induce denitrification declined with soil depth, suggesting a decline in the denitrifier population with depth. Significant reduction in N loss from mangrove soil after adding nitrification inhibitor indicates that nitrification is the key factor in N loss of mangrove soil. As there was no significant difference in denitrification between rhizosphere and non-rhizosphere soil, the cause of N loss in the mangrove soil may occur primarily in the surface soil rather than in the rhizosphere soil.