The Effect of Organic-Based Nutrient Management Strategies on Soil Nutrient Availability and Maize Performance in Njoro, Kenya

Abstract

A field experiment based on the concept of organic nutrient management was conducted in Njoro, Kenya, to test the effect of improved legume fallows, crotalaria (CR), lablab (LB), garden pea (GP) and natural fallow (NF, as control) on available soil N and P and maize performance. The experimental design was a split plot fitted to a randomized complete block. The main plots were two cropping systems involving the improved legume fallows and NF preceding sole maize and maize–bean (M/B) intercrop. The sub-plots were two residue management types: residue incorporation and residue removal with farm yard manure (FYM) incorporated instead. Residue incorporation resulted in higher concentrations of N and P in soil than FYM in both cropping systems. Under sole maize, grain yield following LB was significantly higher than after CR, GP and NF. In the M/B intercrop, maize grain yield following LB was significantly higher than after GP and NF, with no significant differences in yields following CR and LB. Maize dry matter (DM) yields followed a similar trend. Overall, maize grain and DM yields were higher in sole maize cropping system than in M/B intercrop but an additional 0.5–0.6 kg ha–1 of bean grain yield was realized in the latter cropping system. The improved fallow legumes enhanced soil productivity, besides the seeds providing ancillary protein in diet locally, with resultant higher yields of the succeeding crop.