Nitrogen fixation in perspective: an overview of research and extension needs

Recent reports point to a decline in agricultural dependence on symbiotic nitrogen (N-2) fixation, and in the use of rhizobial inoculants. This review contrasts the potential contribution of biologically fixed N to intensive and extensive agricultural systems, and examines opportunities for continued major contributions in the latter, It identifies six research and extension areas in which in-depth efforts are still needed, and examines some opportunities for improved N-2 fixation likely to arise through advances in molecular biology. (C) 2000 Elsevier Science B.V. All rights reserved.