EFFECTS OF COLOURED PLASTIC MULCH ON SOIL HYDROTHERMAL CHARACTERISTICS, GROWTH AND WATER PRODUCTIVITY OF RAINFED SOYBEAN

Abstract Soil thermal regime, a crucial factor in plant growth and development, is influenced by the colour of plastic mulch. The effects of black plastic mulch (BPM), silver plastic mulch (SPM), transparent plastic mulch (TPM) and bare soil on the soil temperature regime as well as on the growth and yield of rainfed soybean were evaluated in a field experiment. The results revealed a strong correlation ( r 2 = 0.85) between air and soil‐surface temperatures in the case of bare soil, but no correlation ( r 2 = 0.03) in the case of TPM. The coloured plastic mulching raised soil temperature by 3–7 °C compared to bare soil, with a daily fluctuation of 6–17 °C at the early growth stage, while the soil temperature increased by 1–2 °C, with a daily fluctuation of 4–8 °C in later growth stages. BPM provided 1–4 °C more temperature than SPM and TPM at 5, 15 and 25 cm depths that augmented heat accumulation by 23% and 6% compared to bare soil and TPM, respectively. The coloured mulching significantly ( p < 0.05) increased soybean growth attributes and thus augmented seed yield by 31–34% compared to bare soil. However, BPM, by maintaining the highest soil temperature, provided the highest seed yield of soybean. Therefore, BPM is recommended as a suitable mulch in the central Japan area. © 2020 John Wiley & Sons, Ltd.