Abstract
Investigations were made on the growth and yield of soybean in terms of soil temperature and soil water potential under mulching with coffee residue and polyethylene film. 1) Mulching with coffee residue and polyethylene film markedly decreased weed biomass and increased the growth and pod yield of soybean in contrast to unmulched control soil. 2) After the cultivation of soybean, the soil mulched with coffee residue possessed higher contents of inorganic N and total N than the unmulched control soil and soil mulched with polyethylene film. 3) The minimum temperature was about 3℃ higher in the soil mulched with coffee residue than the unmulched control soil, and about 1℃ higher than the soil mulched with polyethylene film. However, the soil mulched with coffee residue maintained the lowest level of maximum soil temperature when compared to the other treatments. 4) The control soil and soil mulched with polyethylene film exhibited a large lowering of soil water potential during the drying period. However, the water potential in the soil mulched with coffee residue was almost constant throughout this study. 5) The decomposition of soil mulched with coffee residue was slow. Therefore, it is believed that mulching effects, such as weed control, soil temperature and soil water potential, extend the harvesting time of soybean. From these results, it is believed that mulching with coffee residue enhances the growth and pod yield of soybean by increasing the minimum soil temperature and soil water potential.
