This symposium organised by the International Rice Institute concentrate on the P requirement to optimize food and fiber production in the main rice-growing areas of the world using Asia and Oceanic data in a regional case study. Research gaps and needs are discussed

Rice ecosystems; Nutrient management; Mineral deficiencies; Mineral toxicities; Tools and information.

This book summarise advanced knowledge and methods to recycle waste and fertilise soils in agriculture. In the near future, waste recycling will no longer be an option because natural resources become rare and costly, urbanisation is blooming and population is growing. In theory, most waste could be recycled. In practice, most waste is wasted. Remarkable aspects include the concepts of waste hierarchy eco-houses in smart cities, microbes and fungi for plant nutrition, and benefits of legume cultivation, biochar application and agropastoralism.

Selected papers from a symposium held as part of the 1992 International Rice Research Conference.

Chemical fertilizers have had a significant impact on food production in the recent past, and are today an indispensable part of modern agriculture. On the other hand, the oil crisis of the 1970s and the current Middle East problems are constant reminders of the vulnerability of our fossil fuel dependent agriculture. There are vast areas of the developing world where N fertilizers are neither available nor affordable and, in most of these countries, balance of payment problems have resulted in the removal of N fertilizer subsidies. The external costs of environmental degradation and human health far exceed economic concerns. Input efficiency of N fertilizer is one of the lowest and, in turn, contributes substantially to environmental pollution. Nitrate in ground and surface waters and the threat to the stability of the ozone layer from gaseous oxides of nitrogen are major health and environmental concerns. The removal of large quantities of crop produce from the land also depletes soil of its native N reserves. Another concern is the decline in crop yields under continuous use of N fertilizers. These economic, environmental and production considerations dictate that biological alternatives which can augment, and in some cases replace, N fertilizers must be exploited. Long-term sustainability of agricultural systems must rely on the use and effective management of internal resources. The process of biological nitrogen fixation offers and economically attractive and ecologically sound means of reducing external nitrogen input and improving the quality and quantity of internal resources. In this book, we outline sustainability issues that dictate an increased use of biological nitrogen fixation and the constraints on its optimal use in agriculture.

The book deals with agroecological aspects of nutrients essential to crop production. A new concept termed 'AGROSPHERE' has been introduced in the book. A brief description about agrosphere, its expanse, contrasting features and interactions with other ecospheres, global nutrient dynamics and food production trends within various agro ecosystems fo