INTEGRATED IRRIGATION AND DRAINAGE PRACTICES TO ENHANCE WATER PRODUCTIVITY AND REDUCE POLLUTION IN A RICE PRODUCTION SYSTEM

Water-saving irrigation and controlled drainage have been separately practised in many countries to increase water use efficiency and reduce non-point source pollution while maintaining crop yields. In a two-year field experiment in the Gaoyou Irrigation District of South China, water use, crop yield, and pollution loads were monitored in an integrated water-saving irrigation and controlled drainage (WSI-CD) system and an unregulated system. For both 2007 and 2008, irrigation water productivity (WPI) and gross water productivity (WPG) of the WSI-CD were 45.3 and 31.6% higher than those of the unregulated system. While evapotranspiration water productivity (WPET) of the WSI-CD was similar to or even less than that of the unregulated system, this indicated that a reduction in irrigation water did not cause water stress and the WSI-CD only reduced non-productive water use. In 2008, the amount of drainage water from WSI-CD (1956 m(3) ha(-1)) was far less than the unregulated system (4255 m(3) ha(-1)), and TN and TP loads were significantly reduced by 50.9 and 52.3%.The water-saving irrigation practice contributed to lower drainage potential, while the controlled drainage reduced irrigation requirements. The integrated WSI-CD practices seemed to have the desirable functions of water saving and pollutant reduction. Copyright (c) 2011 John Wiley & Sons, Ltd.