Soil nitrogen amendment effects on maize productivity under two different soil conditions in western Kenya.

Abstract

The effect of integrated use of urea and calliandra or maize stover on yield and N uptake of maize was assessed in a field experiment carried out on two soil types in western Kenya. Urea and calliandra or maize stover were combined in a way to supply N at 75 kg ha-1 from both sources in 0:0, 100:0, 80:20, 60:40, 40:60, 20:80, 0:100 ratios arranged in randomized complete block design (RCBD) with 12 treatments replicated four times. Maize hybrid (WS 502) was used as a test crop. Data on total biomass, grain, stover and cob yields of maize were recorded at harvest. Samples from grain, stover and cobs were analyzed for total N to determine its uptake by the crop. Overall results for the two sites in both seasons realized highly significant (p<0.05) differences between nitrogen rates for grain yield and significant (p<0.05) differences for cob yield and total biomass. A combination of 30 kg N from organic material and 45 kg N from urea (40:60%) ratio or 45 kg of N from organic material and 30 kg N from urea (60:40%) gave the highest yields. Pure maize stover as a source of N gave the lowest yields. The two sources of organic nitrogen (calliandra and stover) gave significantly different (p<0.05) results for grain yield, cob yield and total biomass, but were not significantly different (p>0.05) for stover yield. Calliandra as a source of N gave consistently higher yields than stover. These results suggested that integrated use of urea and calliandra or maize stover performed better than the urea, calliandra or maize stover alone in terms of improving crop and N yields of maize despite the fact that the levels of applied N was the same i.e. 75 kg N ha-1 either alone, from urea, stover or combinations of urea and either of the two organic sources.