Nitrogen Use To Improve Sustainable Yields In Agricultural Systems

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.

Reprinted from Plant and Soil, v.174, nos.1-2 (1995), this volume is devoted to discussions on the role of biological nitrogen fixation (BNF) in agricultural sustainability. Papers presented on BNF in crop forage and tree legumes are augmented with discussion of integrated farming systems involving BNF, soil and N management, and recycling of legume residues. BNF by non-legumes is discussed and attempts to transform cereals into nodulating plants are critically reviewed. Also described are advances in the development of new methodologies to understand symbiotic interactions and to assess N-2 fixation in the field; means of enhancing BNF through plant and soil management; breeding and selection; problems encountered in exploiting BNF under farmers' field conditions; and promising approaches to improve BNF exploitation. Lacks a subject index. Annotation copyright by Book News, Inc., Portland, OR

Most plants absorbmore nitrogen than any other nutrient. Because the amount needed is so large and easily be lost from many soils, nitrogen is usually the most limiting nutrient for plant growth. Although about 79 percent of the atmosphere is nitrogen, only nitrogen-fixingplants such as legumeswith their associated bacteria are able to use this abundant source. The nonleguminous grain crops must receive supplemental nitrogen to produce satisfactory yields. Until the last few decades the supply of available nitrogen in the soil was increased primarily by legumes and manure. These sources should be used when economically feasible, but many important grain-producing areas of the world must now rely on commercial fertilizer nitrogen. For economic reasons researchers and growers have been interested for many years in improving yields from each unit of nitrogen. Recently, however, the efficient use of nitrogen has become an environmental issue as well, because high nitrate concentrations in water may be harmful to humans, especiali infants, and to livestock. If plants absorb more of the addedfertilizer nitrogen, then less is likely to leach from fields into drinking water. Improving nitrogen efficiency has also become crucial in order to conserve dwinling supplies of natural gas, which is used in large quantities to manufacture nitrogenfertilizers.

In the last 20 years, there has been a remarkable emergence of innovations and technological advances that are generating promising changes and opportunities for sustainable agriculture, yet at the same time the agricultural sector worldwide faces numerous daunting challenges. Not only is the agricultural sector expected to produce adequate food, fiber, and feed, and contribute to biofuels to meet the needs of a rising global population, it is expected to do so under increasingly scarce natural resources and climate change. Growing awareness of the unintended impacts associated with some agricultural production practices has led to heightened societal expectations for improved environmental, community, labor, and animal welfare standards in agriculture. Toward Sustainable Agricultural Systems in the 21st Century assesses the scientific evidence for the strengths and weaknesses of different production, marketing, and policy approaches for improving and reducing the costs and unintended consequences of agricultural production. It discusses the principles underlying farming systems and practices that could improve the sustainability. It also explores how those lessons learned could be applied to agriculture in different regional and international settings, with an emphasis on sub-Saharan Africa. By focusing on a systems approach to improving the sustainability of U.S. agriculture, this book can have a profound impact on the development and implementation of sustainable farming systems. Toward Sustainable Agricultural Systems in the 21st Century serves as a valuable resource for policy makers, farmers, experts in food production and agribusiness, and federal regulatory agencies.

Nitrogen is an important agricultural input that is critical for crop production. However, the introduction of large amounts of nitrogen into the environment has a number of undesirable impacts on water, terrestrial, and atmospheric resources. This report explores the use of nitrogen in U.S. agriculture and assesses changes in nutrient management by farmers that may improve nitrogen use efficiency. It also reviews a number of policy approaches for improving nitrogen management and identifies issues affecting their potential performance.

Review of the principles and management implications related to nitrogen in the soil-plant-water system.

Sustainable agriculture embodies many concepts in its attempt to integrate all the aspects of farming systems into a holistic system. This book explores the processes that occur within the components of a sustainable system and shows where we can build upon our existing knowledge to develop the concepts of sustainable agriculture into the new conventional agriculture. Well-known researchers examine a variety of aspects, including production goals, environmental considerations, and economics, to build a knowledge base that allows readers to see where changes in agriculture must be made and how challenges can be met. They compare existing systems against definitions of sustainability and pinpoint those areas where improvements can be made in current systems to further the concepts of sustainability.