Evaluating commercial arbuscular mycorrhizal fungi (AMF) on soybean in Kenya

Mycorrhizal technologies are being developed around the world as a suitable answer to crops yields increases, lowering farmers cost inputs and modern agriculture improvement. But, many studies already pointed out products incapability to improve plants yield or, attributed increases to added ingredients. In the frame of the COMPRO project funded by Bill and Melinda Gates Foundation, we evaluated under greenhouse conditions 13 commercial Arbuscular Mycorrhizal Fungi (AMF) products on soybean using a sandy and a clay soil and two sources of Phosphorus before assessing the most promising products in different agro-ecological zones of Kenya. Results from greenhouse indicated 11 products significantly increasing plants roots colonization by mycorrhizae in both soils. However, any product was able to improve plants growth in the clay soil and only 2 products did it in the sandy soil. Assessment of most promising products from greenhouse trials in subsequent field trials in 3 agro-ecological zones of Kenya showed still good roots colonization but, any significant effects on yield compared to control and usual fertilizers. Preliminary tests under local soil context must be conducted before large-scale use of commercial AMF bio-inoculants and synergetic effects with other soil microorganisms should be looked for. (Résumé d'auteur