Effects of manure application timing on rice water productivity, nutrient leaching, and runoff under monsoon climate

Abstract

Improving water productivity for rice production and maintaining water quality are grave concerns in many Asian countries. Animal manure application has the potential to improve soil nutrient status and alter soil hydraulic properties, but its application timing can variably influence nutrient release to nearby water bodies and the water productivity. We quantified the water productivity, rice yield, and nutrient leaching and runoff potential in irrigated fields under different manure application scenarios, namely no manure applied (NoM), dry manure applied in winter (DMW), fresh manure applied in winter (FMW), and dry manure applied in summer (DMS). Manure application significantly increased the grain yield (31, 44, and 46% by DMW, FMW, and DMS, respectively) and straw yield compared to the NoM scenario. The DMS scenario gave the highest yield (6.8 Mg/ha) and harvesting index (44.8%). The irrigation requirement and percolation loss decreased under the DMW and DMS scenarios. The scenarios with manure application had higher water productivity (0.51–0.64 kg/m3) than the NoM scenario (0.39 kg/m3). Manure application did not influence the leaching and runoff loss potential of N; however, NoM had the highest leaching concentration of N (5.25 mg/L). The highest concentrations of P in leachate (0.52 mg/L) and ponded water (3 mg/L) were observed for DMS, followed by the FMW scenario. The DMS scenario showed higher agronomic performance with a higher risk of nutrient spreading. To reduce the nutrient spreading in the monsoon with no considerable yield loss, the DMW can be the best scenario in this study area. A long-term study could comprehensively clarify the effects of these practices on soil health and water quality.