Efficacy of organic mulches on soil water conservation, weed incidence and crop water productivity in summer rice

A field experiment was conducted to assess the impact of organic mulches on soil water status, root growth, weed incidence and crop water productivity of IET 4786 in dry season under rotational submergence (RS) against continuous submergence (CS). Bio-mulches like Azolla microphylla, rice chaff, saw dust, subabool (Leucaena leucocephala L.) green leaf and farm yard manure were applied in rotational submergence at 15 days after transplanting. Irrigation at 5 days interval (RS) decreased the soil water status in rice by >30% but application of mulches helped to maintain a higher (15.9 - 20.8%) soil water status in root zone at different stress cycles. RS saved about 30% irrigation water over CS but alternate wetting and drying under RS caused much soil cracking of puddled soil, restricted root growth and increased the weed growth. The lowest water productivity (0.35 kg m−3) was recorded under rotational stress. However, application of bio-mulches improved the field water use efficiency by 19.7% to 41.2% over continuous submergence and 20 to 54% over rotational stress control. Mulching reduced the water cost for grain production by up to 37%.