Evaluation of the Potential of Using Nitrogen Fixing Legumes in Smallholder Farms of Meru South District, Kenya

Soil fertility depletion in sub-Saharan Africa is a big constraint to increased food production to feed the ever-growing human population. Use of legumes to improve soil fertility is an option in the central highlands of Kenya and this study evaluated soil characteristics on farms and screened effectiveness of five rhizobia strains on four legumes. Soils sampled from 31 farms showed that the soils were generally acidic with more than 50% of the farms having pH in the range of extremely acidic and strongly acidic (pH < 5.0). Organic carbon was low (<2%) on most farms and total nitrogen was deficient with more than 80% having <0.2% N while P ranged from 1.3 to 15.8 ppm with more than 70% of the farms being critically deficient in P. Nodulation on Mucuna pruriens and Crotalaria ochroleuca was observed to be variable within farms with individual farms having fewer nodules per plant than on-farm researcher managed trial. Consequently trials to evaluate effectiveness of rhizobia strains were conducted under glass house conditions. Results showed that KWN35 and TAL 1145 were highly effective on C. calothyrsus and L. trichandra and not on C. ochroleuca. Crotalaria ochroleuca nodulated effectively only with CP354 and NGR457. The NGR 457 was highly effective on all the legume plants while NGR185 was only effective on L. trichandra. These studies showed that performance of legumes among the smallholder farms was likely to vary due to varying soil characteristics and that there could be potential for improving legume performance within the smallholder farms through inoculation