|Graham, Peter - UNIVERSITY OF MINNESOTA|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: December 14, 1995
Publication Date: N/A
Technical Abstract: Nitrogen is the limiting nutrient for most plant species. Acquisition of nitrogen is second in importance only to photosynthesis for plant growth and development. Of the reduced nitrogen that is annually available for assimilation by plants, approximately 65% is derived from biological nitrogen fixation. Over the past 50 years, significant progress has been made in understanding the biology, ecology, and molecular genetics of biological nitrogen fixation. However, in developed countries during this same period the use of biological nitrogen fixation in cropping systems has decreased precipitously. This has been due primarily to the availability of inexpensive fixed nitrogen produced by the Haber Bosch process and the release of crop cultivars which have highly positive responses to added nitrogen fertilizer. These advances have led to the overuse of commercial nitrogen fertilizer, resulting in significant water and air pollution. By contrast, in developing countries the high potential for use of biologically fixed nitrogen to either substitute for or augment commercial fertilizer nitrogen has not been achieved due to both social and economic policies. Sustainable (renewable) agricultural practices necessitate that biological nitrogen fixation be incorporated more effectively into cropping systems in both developed and developing countries. Judicious management of biologically fixed nitrogen in agriculture can be not only environmentally prudent but also economically sound. Research priorities in biological nitrogen fixation should focus on: genetic improvement in the host; factors that contribute to rhizobial strain competition and persistence; use of biologically fixed nitrogen in cropping systems; and methods for enhancing the use of biotechnology in nitrogen fixation.