Soybean (Glycine max (L.) Merr) response to biofix (Bradyrhizobium japonicum), trianum (Trichordema harzianum t-22) and phosphorus in poorly responsive soils of western Kenya

Declining soybean yields in western Kenya due to low soil fertility is a threat to farmers’ goals of generating income for improved livelihoods. Though commendable success has been observed after use of both phosphate (P) fertilizers and Biofix (Rhizobium inoculant), there is still a wide gap of attaining the potential yield in poorly responsive soils. This could be an indication that other factors such as soil physiochemical properties might be limiting. A greenhouse experiment was, therefore, conducted in University of Eldoret-Kenya, using two poorly responsive soils from Busia-North and Bungoma-Southwest to assess crop performance when Trianum, a Trichoderma inoculant was added to both Biofox and P fertilizer. While both soils had generally low nutrient status, Bungoma-Southwest soils were moderately acidic (5.4) compared to almost neutral pH in Busia-North (6.2). The experiment layout was a factorial in a completely randomized design, with sixteen treatments each replicated four times. The treatments consisted of (i) absolute control (with no fertilizer application), (ii) sole application of either inoculants or P and (iii) various combination of the three. Results indicated that the use of inoculants together with the P fertlizer improved in soybean yields (biomass) and nodulation in Busia-North soils compared to Bungoma-Southwest soils. Key words: Inoculants, N-fixation, poorly responsive soils, soil pH, soybean biomass