Weed density and biomass are reduced and plant growth and seed yield increased in common bean after solarisation with clear and black plastic

Abstract

Common bean is highly sensitive to early weed competition, which severely reduces growth and yield. An experiment was carried out in Zimbabwe in the 2002/03 and 2003/04 seasons to assess the effectiveness of solarisation in controlling weeds in beans. Four pre-planting treatments, viz. covering plots with (1) clear plastic and (2) black plastic for eight weeks from September to November, (3) fumigation with methyl bromide and (4) an untreated control, were laid out in a randomised complete block design with four replicates. Soil temperature at 5 cm depth was significantly (p < 0.05) higher in the clear plastic treatment (39–55 °C) than the black plastic (30–43 °C), fumigated (37–41 °C) and uncovered treatments (30–40 °C). Mean weed emergence and biomass significantly (p < 0.001) increased in the order clear plastic < black plastic < fumigated < uncovered in the bean crop at 5 weeks after emergence. Number of flowers and pods plant−1 (p < 0.001) increased by 30% and 44% in the black plastic and clear plastic solarised treatments. Bean seed yield (p < 0.001) increased by 13%, 68% and 86% (2002/03 season) and by 27%, 77% and 83% (2003/04 season) in the fumigated, black plastic and clear plastic solarised treatments, respectively. The increased bean growth and seed yield is a result of solarisation reducing weed density and inducing beneficial soil amendments.