Oct. 2010, Volume 4, No.6 (Serial No.31) Journal of Life Sciences, ISSN 1934-7391, USA Financial Value of Nitrogen Fixation in Soybean in Africa: Increasing Benefits for Smallholder Farmers Jonas Nwankwo Chianu 1, 2 , Jeroen Huising 1 , Seth Danso 3 , Peter Okoth 1 , Justina Nwanganga Chianu 1 and Nteranya Sanginga 1 1. Tropical Soil Biology and Fertility Institute of the International Centre for Tropical Agriculture (TSBF-CIAT), Nairobi 00100, Kenya 2. Agricultural Fertilizer Financing Mechanism (AFFM), OSAN, ATR 808/B, AfDB, BP 323–1002 Belvedere, Tunis 1002, Tunisia 3. Ecological Laboratory, University of Ghana, Legon- Accra 00233, Ghana Received: February 1, 2010 / Accepted: August 16, 2010 / Published: October 30, 2010. Abstract: 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 t -1 (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. Key words: N 2 -fixation, promiscuous soybean, financial valuation, Africa. 1. Introduction Soil organisms contribute essential services to sustainable functioning of agro-ecosystems [1]. However, few studies have been undertaken to measure the financial implications of these services and their importance in the sustainable conservation and management of soils. Of specific interest are legume nodulating bacteria (LNB) that form symbiotic associations with a leguminous host plant providing nitrogen to the host for which it gets carbohydrates in return as an energy resource. In agriculture advantage Corresponding author: Jonas Nwankwo Chianu, Ph.D., research fields: agricultural commodity market development, agricultural economics and improved agricultural technology adoption. E-mail: jchianu@yahoo.com. is taken of this ability to fix nitrogen by growing legume crops like soybean (Glycine Max), cowpea (Vigna unguiculata), common bean (Phaseolus spp), groundnut (Arachis hypogea) and others, all of which generally have the ability to nodulate with a wide variety of rhizobium strains in the soils (hence are generally referred to as being promiscuous) [2-4]. A substantial portion of the world’s supply of organic nitrogen is fixed via the symbioses between root-nodulating bacteria and leguminous host plants [5]. Estimates available indicate that biologically fixed nitrogen in agricultural field is about double of the nitrogen produced industrially. For example, a mix of the legume cover crops (LCC) Pueraria phaseoloides and Calopogonuim caeruleum could supply