Effect of Biochar and Vermicompost Soil Amendments on Fungal Root Rot Disease of Common Bean in Western Kenya.

Common bean (Phaseolus vulgaris L.) is a grain legume grown on more than four million ha annually in Africa and provides dietary protein for over 100 million people in rural and poor urban communities. Soil borne pests and diseases are a serious challenge in agricultural production systems, especially if crops are grown repeatedly in the same field without crop rotation. Root rot diseases are often considered the major constraint to bean production, reducing both yield and quality leading to as much as a 70% reduction in yields of some popular commercial bean cultivars in Kenya. We sought to establish the incidence and severity of fungal root rot disease on beans grown on small-holder farms in Western Kenya and to use organic matter amendments (vermicompost and biochar) to reduce their incidence and severity. Farms are located in three regions of western Kenya, representing four agro-ecological zones. Disease incidence was recorded during plant growth and pathogens isolated from the diseased roots to establish the cause of the disease as well as to identify the pathogens. Pathogen propagule populations in soils sampled as well as disease severity varied across the different regions and at different stages of plant growth. Two years of field data indicate that both biochar and vermicompost soil amendments reduced disease incidence and improved bean yields when used separately and in combination, relative to control plots. The use of these organic soil amendments can help small scale farmers achieve greater agronomic success, higher yields and more reliable return on their investments in bean cropping as well as address constraints to bean production sustainably.