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.

Reports on recent research designed to help increase the productivity of scarce tropical farmland without damaging the environment by gaining a better understanding of the chemical, biological, and ecological aspects of relationships between the critical element nitrogen in plants and soils. Describes the use of isotopically- labeled nitrogen in experimentation, the impact of the tropical environment on nitrogen transformation in the soil, annual fluctuations of native available soil nitrogen, the interaction of major fertilizers with different soils, the role of micro-flora in nitrogen availability, the behavior of applied nitrogen in wet and submerged soils, and advances in nitrogen-fixing by Rhizobium- legume symbiosis. All but 10 of the 42 papers are reprinted from Fertilizer Research vol. 42 nos. 1-3 (1995). No index. Annotation copyrighted by Book News, Inc., Portland, OR

Nitrogen Economy in Tropical Soils presents an authoritative and comprehensive state-of-the-art review on soil/plant nitrogen inter-relationships, with special reference to tropical soils and crops in aerobic and anaerobic environments. Use of isotopically labelled nitrogen in experimentation, especially in tropical environments, and recently developed analytical techniques for soil and plant materials are presented. An important aspect is the emphasis placed on the impact of the tropical environment on nitrogen transformations in the soil environment. This book should be an excellent source of information for senior undergraduate and graduate students with interest in soil/plant nitrogen inter-relationships, and for all levels of research workers in these fields.

"The overall objective is to develop a commercial test to predict soil N supply to rice"--P. 3.