Mulching type-induced soil moisture and temperature regimes and water use efficiency of soybean under rain-fed condition in central Japan

Soybean (Glycine max) is a high water-demand crop and grown under moderate temperature in Japan. To protect the crop from hot summer and to utilize rainfall for its cultivation, selection of appropriate mulching material(s) is crucial. For optimum production of the crop, soil moisture and temperature regimes as well as water use efficiency (WUE) of the crop were investigated under straw, grass, paper, plastic and bare soil (control) mulching under rain-fed condition at Gifu university farm in Japan. The mulching treatments, compared to the control, lowered soil temperature by 2 °C at 5 cm depth and 0.5 °C at 15 and 25 cm depths. The plastic and straw mulching stored the highest quantity of soil moisture at 5 and 15 cm depths; the bare soil stored the lowest quantity. At 25 cm depth, soil-moisture content was the highest under paper mulch but invariable under the other mulches. Plastic mulching reduced evaporation rate from the soil surface and, consequently, the reduced soil-water consumption (SWC) from the root zone augmented WUE of soybean. The paper mulching, by conserving soil-moisture and reducing soil temperature, provided better crop growth attributes, while the plastic mulching improved WUE of green soybean. Therefore, the plastic mulch performed best in reducing soil-water consumption and increasing WUE, while the paper mulch was good for soil-moisture conservation and temperature modification that increased soybean yield.