Improving Soil Fertility - through Biological Nitrogen Fixation

Improving Soil Fertility through Biological Nitrogen Fixation Biologically fixed nitrogen is an alternative source to inorganic nitrogen fertilizer for crop growth. Major grain legumes are estimated to fix approximately 11,1 million metric tons of nitrogen per annum from the atmosphere in developing countries as measured by stable isotope methodologies.

The SWMCN Subprogramme through nine Coordinated Research Programmes and several Technical Cooperation Projects in Member States (1975 to present) has contributed to the enhancement of biological nitrogen fixation (BNF) in developing countries. If the above mentioned amount of nitrogen (N) would be supplied by N fertilizers, approximately 7 billion US$ would have to be spent. It is thus reasonable to conclude that these major grain legumes contribute 30-40% of the annual N requirement of developing countries, a contribution that is of great economical and environmental value.

The contribution of BNF to crop production can be enhanced substantially in most regions, as has been done in Brazil where some 35 million metric tons of soybean are being produced annually using cultivars, which have been bred for nitrogen fixation supportive traits. These soybeans do not respond to N fertilizer and are self sufficient in N, with N fixation conservatively estimated at 100 kg N/ha. Similar type of enhancement of BNF could be implemented in other developing countries.

he potential benefit in reducing the need of inorganic nitrogen fertilisers can be enormous if BNF can be optimized with the use of soil and water management practices that are tailor made to local conditions to ensure that N-fixing plants are not constrained by the lack of available soil moisture and other essential nutrients such as sulphur and phosphorus for their growth.