Critical period of weed interference in pure maize and maize/pigeon pea and maize/soyabean intercrops in Malawi
1995
Kumwenda, J.D.T. | Kabambe, V.H.
An experiment was conducted at Chitedze Research Station and on a farmers' field outside the research station in the 1987/88 and 1988/89 growing seasons to determine the critical weed-free requirement and the critical duration of weed interference in pure maize. A similar experiment was conducted at Mbawa and Chitala in 1991/92 to determine the critical duration of weed interference in maize/soyabean, and maize/pigeonpea intercrops. The major weeds present in the weedy control plots in 1987/88 and 1988/89, both on the station and the farmer's field were Eleusine indica, Oxalis sp., Nicandra physalodes, Bidens pilosa L., and Complaina benghalensis. At Chitala, weeds present in the weedy control plots of the maize/pigeonpea intercrop were E. indica, Digitaria ternata, C. benghalensis, Tridax procumbens, Ocimum canum, Celosia trigyna, and Trichoderma zeylanicum. At Mbawa, the dominant weeds in the maize/soyabean intercrop were Hyparrhenia sp., B. pilosa and E. indica. Uncontrolled weed growth caused a 2-year average yield loss of 50 percent in the pure maize experiment. At Mbawa the yield loss due to uncontrolled weed growth in maize/soyabean was 27 percent for maize and 56 percent for soyabeans. At Chitala the uncontrolled weed growth resulted in a maize yield loss of 72 percent. The critical period for weed control in these experiments was found to be within the first 56 days after planting.
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