The steadily increasing cost of nitrogen fertilizer has resulted in more emphasis on basic and applied studies to improve nitrogen use efficiency in lowland rice. The efficiency of fertilizer nitrogen in farmers' fields is shockingly low ~ a luxury resource-scarce farmers in tropical Asia can ill afford. We believe it is critical to quantify the basic transformation processes and develop management practices for higher N use efficiency for two reasons. They are: 1. Nitrogen fertilizer together with water management is a key factor for achieving the yield potentials of modern rices. 2. Fertilizer nitrogen prices are high and most Asian rice farmers are poor. The International Rice Research Institute (IRRI), Philippines; Internation al Fertilizer Development Center (IFDC), USA; Commonwealth Scientific and Industrial Research Organization (CSIRO), Australia; U.S. Universities (Louisiana, Cornell, California, Arkansas and others); and Dr Justus Leibig University in West Germany are actively engaged in individual or collaborative research that addresses basic transformation processes on N gains and losses and management practices to maximize N use efficiency in rice. It is appropriate to update and summarize, in a double issue of Fertilizer Research, the 10 papers presented at the special symposium organized by the American Society of Agronomy (ASA) at the 75th Annual Meeting in Washington, D.C. in 1983. S.K. De Datta, Head of Agronomy Department, IRRI, was chairman of the International Agronomy Division of ASA (A-6) in 1982 and 1983.

Inhalt

1. The Chemistry and Biology of Flooded Soils in Relation to the Nitrogen Economy in Rice Fields.- 2. Nitrogen Transformations in Flooded Rice Soils.- 3. Technologies for Utilizing Biological Nitrogen Fixation in Wet-Land Rice: Potentialities, Current Usage, and Limiting Factors.- 4. Reappraisal of the Significance of Ammonia Volatilization as an N Loss Mechanism in Flooded Rice Fields.- 5. Denitrification Losses in Flooded Rice Fields.- 6. Ammonium Dynamics of Puddled Soils in Relation to Growth and Yield of Lowland Rice.- 7. The Efficacy and Loss of Fertilizer N in Lowland Rice.- 8. New developments in nitrogen fertilizers for rice.- 9. Improving Nitrogen Fertilization in Mechanized Rice Culture.- 10. Improving Nitrogen Fertilizer Efficiency in Lowland Rice in Tropical Asia.