摘要
The knowledge that soil microorganisms form an important component of below ground biodiversity, providing ecosystem services, is often not incorporated in formulation of policies to conserve and manage these microorganisms. Using the method of cost replacement or cost savings in terms of mineral nitrogen fertilizer that would have been required to attain the same level of nitrogen fixed biologically, this study contributes to awareness on the importance of these microorganisms. Applying the knowledge gained from several on-station and on-farm trials in Africa, complemented with assumptions on FAO-sourced data from 19 African countries, this study estimated the financial value of nitrogen fixation of legume nodulating bacteria （LNB） associated with promiscuous soybean varieties. Results show that the financial value of the nitrogen-fixing attribute of soybean in Africa, especially the promiscuous varieties, annually amounts to about $ 200 million US dollars across the 19 countries. With the fertilizer price of -$ 795 tl （June 2008）, this would amount to $ 375 million. The study recommends various ways of increasing the chances of smallholder farmers benefiting from the nitrogen-fixing attribute of LNB, especially since many cannot afford adequate quantities of inorganic fertilizers for increased crop productivity.
