Effect of Kill Time of Legume Green Manures on Growth and Nutrient Uptake of Succeeding Maize (Zea mays L)

Two consecutive field studies were conducted at the experimental site of the Assosa area, western Ethiopia, with the objective to determine the effects of kill time of legume green manures on growth and nutrient uptake of the succeeding maize crop. Factorial combination of four legume crops and four residue managements were laid in RCBD. Species by termination stage interaction effects were observed on legume tissue N and P concentrations. Significant effects of green manure species and residue management were also observed on leguminous dry matter (DM) production, whereby DM input was higher from cowpea and as termination was delayed from mid-vegetative to pod-setting stages of growth, respectively. These effects were also signified in the growth, nutrient uptake and yield of maize crop in the subsequent season. In this regard, plots treated with cowpea, which had the highest biomass and nutrient inputs, and the latest stage of incorporation (pod-setting) produced vigorous maize plants with higher DM and grain yields than the rest species and earlier kill times, respectively. The green manure species and growth stage effects on yield and nutrient uptake of the subsequent maize were proved by significant positive relationships observed between maize grain yield and legume DM input (r = 0.83**), leguminous N input (r = 0.85**), N uptake (r = 0.69*) and P uptake (r = 0.75**). In the present study, the N and P uptakes of maize crop were generally excelled the actual green manure accumulation, implying that cropping systems involving legumes as green manure could probably be the most efficient ones.