Keywords: planting densities, cowpea, green manure, maize.


A field trial was conducted in the University of Agriculture, Abeokuta, a derived savannah ecological zone of Nigeria, between April to September, 2009 and March to August, 2010 to evaluate the response of succeeding maize to planting density and application methods of preceding cowpea green manure.  The green manure was established in a 2 × 3 factorial experiment arranged in a Randomized Complete Block design RCBD. There were three populations densities/ha of cowpea: 30cm×60cm(55,555), 30cm×30cm(111,111) and 30cm×15cm(222,222) and either incorporated or left as mulched six weeks after planting. One week after, maize variety, SUWAN1-SR was planted on all plots and a control plot. Biomass from population densities of 111,111 and 222,222 were similar (p>0.05) and higher (p<0.05) than that obtained from 55,555 in 2009. In 2010, different population produced significantly different biomass from each other, with biomass from 222,222 plants/ha being 52% greater than that from 111,111 plants/ha which was also 84% greater than from 55,555 plants/ha. Grain yield of maize from all incorporated green manure treatments were similar (p>0.05) and significantly higher (p<0.05) than from all mulched applied manure and control treatments in 2009. In 2010 maize grain yield was not significantly different across all treatments and control plots (p>0.05); highest grain yield (p>0.05) were obtained from treatments with both incorporated and mulched cowpea at 222,222 plants/ha. Grain yield of maize from all green manure plots were also higher (p>0.05) than the control plots. It was concluded that 111,111 plants/ha of Oloyin was the optimum for biomass production at 6 weeks after planting, for green manuring. Incorporating preceding cowpea green manure increased grain yield of succeeding maize. Growing cowpea at higher population density cannot make up for the losses of nutrient that would occur if the green manure is not incorporated.



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