Evaluation of Nitrogen Fertility and Increasing Fertilizer Efficiency in Wetland Rice Soils

Abstract

Reactions of fertilizer nitrogen in wetland rice soils are influenced by the presence in the atmosphere above the floodwater of oxygen that moves slowly by diffusion and convection currents to the soil surface. With time, two distinct soil layers are developed: (1) an oxidized surface layer; and (2) an underlying reduced layer. Their thickness depends upon the properties of the soil and the type of water management. Their development under wetland rice culture triggers several physicochemical and microbiological processes. The resultant soil-water-atmosphere system is highly complex and heterogeneous.