Soil Solarization for Managing Weeds in Cabbage Brassica Oleraceae var Capitata in Trinidad and Tobago

A study was conducted to evaluate the effectiveness of soil solarization at the University Field Station (UFS), Trinidad and Tobago, in a cabbage (Brassica oleraceae var. capitata) field naturally infested with weeds. Well prepared pre-irrigated plots 2.4m × 5.4m were covered with 4mm thick clear polyethylene sheeting for the duration of seven weeks from the14th February to 3rd April, 2007. Cow manure was incorporated at a rate of 500m3/ ha in some solarized plots. Non-solarized plots were either treated with pre-emergent pendimethalin at a rate of 4.2L /ha three days after transplanting; treated with glyphosate two weeks before transplanting at a rate of 5L/ha in a stale seedbed preparation or were hand weeded. The cabbage variety salvation was transplanted on the 4th April, 2007. At the end of 10 weeks solarized plots were more effective in controlling weeds. Clear plastic give the best weed control (97.6%) followed by clear plastic + manure (96%) with pendimethalin giving 85.6% control. However, pendimethalin gave a more consistent control of weeds for the duration of the crop. At all stages of assessment of the soil weed seed bank there was no significant difference in the weed count. Clear plastic had the highest yield of 36.45 t/ha and was significantly different from all other treatments. This yield was almost twice that of stale seedbed which gave the next best result of 18.75 t/ha. Pendimethalin had the lowest yield of 4.563 t/ha and seemed to have an adverse effect on the growth of cabbage. Cabbage grew more vigorously on solarized plots. Clear plastic yielded the highest dry matter up to week eight, followed by clear plastic + manure and stale seedbed. At week 10 however stale seedbed produced the highest dry matter of 1.695 kg/m2 but did not differ significantly from clear plastic (1.655 kg/m2). Ten weeks after transplanting there was no significant difference in the weed dry matter among treatments although clear plastic had the lowest dry matter of 0.5g/m2. Soil temperature during solarization was generally higher in plots with only clear plastic than those with manure, averaging 38.86 °C and 37.69 °C respectively between the 43rd and 48th day. Soil solarization with clear plastic can be used as an effective means of managing weeds in cabbage and to increase crop yield.