Influence of different weed categories on growth and yields of maize (Zea mays) grown in a minor (dry) season of the humid tropics

Abstract

Weed control is an important management practice in small-holder tropical upland farming systems, and manual weeding is a common feature in these units. This makes selective weeding possible, which is an essential component of integrated weed management. Field studies were initiated in Sri Lanka over a minor (dry) season to determine the impact of different weeds (grasses, broadleaves and sedges) and non-weeded conditions on the growth and yields of maize, cultivated under rainfed conditions. Weed populations were also determined, along with root distribution of the different weed management regimes at anthesis of maize. The presence of all types of weeds or grasses, which was the most dominant weed category, had the greatest adverse impact on growth and yields of maize. The reductions in seed yield due to the presence of all weeds or grasses alone were 59% and 32%, respectively. In contrast, growth and yields of maize was not affected by the small numbers of sedges present. The impact of broadleaved species was lower than that of all weeds or the grasses. Root distribution through the soil profile was greatest when maize was grown with broadleaved species or with all weeds. The roots of the maize-grass mixtures were concentrated in the upper soil layers. The beneficial impact of removing grasses and broadleaved weeds in selective manual weeding in rainfed maize cultivation which could be practiced by smallholder farming units to obtain higher yields are presented.