Selective control of weeds in an arable crop by mulches from some multipurpose trees in Southwestern Nigeria

The use of agroforestry systems in which pruning from trees is used to mulc h the companion crops is an important area of research in the tropics. Howe ver, previous studies mostly evaluated the contribution of mulch to soil im provement and rarely examined the effect of mulch on weeds. Field experimen ts were conducted during the 1995 and 1996 growing seasons to investigate t he effects of mulch from three woody fallow species on weed composition, bi omass and maize grain yield. Treatments consisted of mulch from Leucaena le ucocephala, Gliricidia sepium, and Senna siamea applied at rates of five an d three tons dry matter ha(-1) at planting and three weeks after planting ( WAP), respectively, an unmulched treatment that received 90 kg N ha(-1) of inorganic fertiliser, and an unmulched control plot that received no fertil iser. In both years and sampling dates, plots mulched with G. sepium and S. siamea had significantly lower weed density and biomass than the control p lot in each of the sampling times and year of study. There was no significa nt difference in either weed density or biomass between the plot mulched wi th L. leucocephala and the unmulched plots. Mulches from G. sepium and S. s iamea reduced weed density and weed biomass, while L. leucocephala was less effective in reducing weed biomass and weed density. Weed reduction by the mulches was in the order G. sepium greater than or equal to S. siamea > L. leucocephala. Sedges were the dominant species in all the treatments excep t in G. sepium plots, where Talinum triangulare and other broadleaved speci es were dominant.