Denitrification Loss of Fertilizer Nitrogen in Paddy Soils--Its Recognition and Impact

摘要

After a large nitrogen loss by denitrification in paddy soils, first recognized in (1941), many field studies to minimize this loss have been conducted in Japan and in all rice-growing countries. The first part of this paper deals with a historical review in Japan of: (a) the discovery of loss of surface-applied nitrogen by denitrification in flooded rice soils, (b) recommendation of deep placement of fertilizer as a measure to minimize loss, (c) innovation of manual and mechanical fertilizer applicators or forms of fertilizers to make deep placement practical, and (d) responses of farmers to the recommendation. The second part describes the international and national efforts in other rice-growing countries to minimize nitrogen loss by deep placement.