Recycling deep percolated water in continuously flooding irrigated rice fields to mitigate water scarcity

摘要

Rice is critical to maintaining nutritional demand and food security of many Asian and African nations. The high water demanding rice is traditionally cultivated with continuous flooding (CF) irrigation practices where 60-90 of applied water can be lost as deep percolation. Burgeoning pressures from other sectoral water demands often challenge flooding rice culture. Existing water conserving rice irrigation approaches are not widely accepted at farmers' level because of compromising yield and/or high operating cost. This study presents the efficacy of a subsurface interceptor system in recycling percolated water for re-irrigating rice fields. The system comprises a pump and filter PVC pipes buried one meter below an experimental rice plot (A) to intercept, store and recycle percolating water. Rice was cultivated in two other adjacent plots (B and C) without an interceptor arrangement where any lateral seepage was restricted in plot B, as did for plot A. There was no such measure for plot C representing a conventional rice field. It was found that plot A produced the highest yield (6.5 t/ha) using the lowest amount of water (650 mm). This could save similar to 50 of water needed for CF irrigated plot C where percolation was the main pathway of water loss (65). Additional energy requirement for recycling intercepted water was overshadowed by the energy burden of pumping larger amount of water against higher system head for plot C. This led the recycling system to produce the highest irrigation water productivity (3.19 kg/m(3)) and energy productivity (8.86 kg/kWh).