A field experiment was conducted during 1998 and 1999 at Jabalpur, Madhya Pradesh, to study the effect of different periods of soil solarization and weed-control measures on weed incidence and productivity of soybean [Glycine max (L.) Merr.]. Mean maximum soil temperature in mulching with transparent polyethylene was 56.4degreesC at surface, 53.6degreesC at 5 cm, 44.3degreesC at 10 cm, and 39.4degreesC at 15 cm soil depths which was higher than non-solarized plots by 10.2, 9.4, 5.1 and 3.4degreesC respectively. Soil solarization for 5 weeks reduced the emergence of jungle rice [Echinochloa colona (L.) Link] by 95%, wild jute (Corchorus) by 83%, common dayflower (Commelina communis L.) by 80% and gripe weed (Phyllanthus fraternus Webster; syn P. niruri Hook. f., non L.) by 58%. Solarization for 5 weeks resulted 82% and 90% reduction in weed population and weed dry weight respectively. Solarization for 5 weeks being at par with 4 weeks also produced significantly higher leaf area and crop dry matter/plant over rest of the treatments. Solarization with transparent polyethylene markedly increased the yield attributes, viz pods/plant, 1000-seed weight and seeds/pod, and seed yield of soybean. The highest seed yield of soybean (1645 kg/ha) was recorded with solarization for 5 weeks, being 110% higher than nonsolarized control. Presence of weeds throughout the growing season caused 35% loss in seed yield of soybean. Amongst the weed-control measures, the highest seed yield of soybean (1478 kg/ha) was achieved with 1 hand-weeding at 20 days crop stage.
