The effects of clear and black plastic mulch on soil temperature, weed seed viability and seedling emergence, growth and yield of tomatoes
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An experiment was carried out from 30 March to 24 August 1994 to compare the effects of clear and black plastic mulch against an uncovered control on soil temperature, weed seed viability and weed seedling emergence and height and yield of tomatoes (Lycopersicon lycopersicum L. cultivar Moneymaker). Mean weekly soil temperatures at 2 cm depth at 1400 hrs were highest under the clear plastic and were generally lowest under the black plastic covers. The plastic covers did not affect the viability of weed seeds in soil samples collected from 0-3 and 0-5 cm depths at 6 and 10 weeks after transplanting (WAT) respectively. When the plastic mulch was removed at the end of the experiment, significantly more weeds (P<0,05) had emerged under the clear plastic (324 weeds per m2;) than in the uncovered control (99 weeds per m2) and under the black plastic (6 weeds per m2). Plant height at 12 WAT, number of plants with flowers and fruits at 7 WAT and 10 WAT respectively, were similar in the black and clear plastic treatments, but were lower (P<0,05) in the uncovered control. Yield was similar among the three treatments during the first four weekly harvests but plastic mulching resulted in significantly higher yields (P<0,05) than the control in the last three weeks of harvesting. Cumulative yield over the 7-week harvesting period significantly differed (P<0,01) among the three treatments being 18,6; 14,8 and 7,82 tonnes per ha for the clear plastic, black plastic and uncovered control respectively. The plastic mulching treatments enhanced tomato plant growth and yield by changing the temperature and light micro-environment around the plants.