Weed competition in cabbage: effect of weeds on yield and damage due to other pests
1988
Kuerschner, E. (International Rice Research Inst., Los Banos, Laguna (Philippines))
The importance of weed competition in transplanted cabbage (Brassica oleracea L. var. capitata) was investigated in field experiments conducted during the dry and wet seasons of 1984 at Nu'u Crop Development Station, Dept. of Agriculture, Western Samoa. Yields did not differ significantly between seasons. The weed flora was dominated by species common in vegetable fields, like Physalis angulata, Euphorbia hirta, Phyllanthus amarus, and Portulaca oleracea as well as Brachiaria subguadripara and Digitaria spp. Its composition changed during the experiment depending on the treatment. Marketable yields reached 13.2, 13.6, and 16.3 t/ha, in plots weeded until six WAT [weeks after treatment], weeded from two WAT, and kept weed free. Weed competition reduced biomass and marketable yields considerably if weed growth was allowed for more than two WAT or if weeding stopped before four WAT. Yield losses averaged 72% in plots weedy until four WAT and 40% if weeding was not continued beyond four WAT. Leaf damage (average disease index) due to head rot, slugs/snails as well as insects varied, depending on season and weed control, from 0 to 16%, 2 to 24%, and 0 to 17%, respectively.
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