The transformations and balance of nitrogen in Japanese paddy fields

Abstract

Research on the transformations and balance of nitrogen in Japanese paddy field is reviewed. During the past decade substantial progress has been made in estimating more accurate nitrogen balance. However, available data do not provide reliable assessments of nitrogen losses or gains, especially of biological nitrogen fixation, denitrification and leaching. Accordingly, data obtainable now permit only a partial accounting of the nitrogen balance in flooded paddy soils. Accurate estimates on inputs and outputs of nitrogen are required. The problems in estimating these gains and losses are discussed, and the need for more nitrogen balance studies in the field is emphasized.