Irrigation Management Effects on Yield and Water Productivity of Inbred and Aerobic Rice Varieties in Kaifeng

摘要

Kaifeng City and it' s surroundings face water scarcity, especially for their rice -growing areas. There is a need to reduce water inputs to rice so that water can be diverted to other users. Aerobic rice is a new way of growing rice: it grows in nonpuddled soil without flooding and can be supplementary irrigated like other crops such as maize. To achieve high yields under aerobic conditions, special "aerobic rice varieties" are being developed. Experiments conducted at two contrasting sites with respect to water table depth (WTD) were carried out in 2001 (WTD approximately 20 cm) and 2002 (WTD > 200 cm) to determine whether aerobic rice can be grown successfully at Kaifeng, and to compare the effects of water- saving irrigation technologies on yield, irrigation water input, and water productivity of aerobic and lowland rice varieties. Water treatments were continuous flooding (CF), alternate wetting and drying (AWD) , and flush irrigation (FI) . The varieties used were lowland inbred 90247 and aerobic rice HD502. All treatments were established by transplanting. The aerobic variety yielded significantly less than the lowland variety, especially in water regimes that maintained high soil water potentials. This was probably caused by reduced tillering and a shorter growth duration of the aerobic variety. In 2001, CF had the highest irrigation water inputs, followed by AWD and FI. FI had higher water productivity (per unit irrigation and per unit irrigation + rainwater) than CF and AWD. Among the FI treatments in 2002, water input declined sharply when the threshold soil water potentials (at which irrigation was applied) were reduced from - 10 to - 70 kPa. Yields of both varieties did not differ significantly among water treatments when the water table was shallow (in 2001) . When the water table was deep (2002) , yield declined with decreasing threshold soil water potentials, especially with the lowland variety. Treatments with threshold potentials of - 10 kPa had significantly lower water productivities than those with lower threshold potentials. The findings showed that the response of yield and water productivity to irrigation regimes depended on the depth of the groundwater and that aerobic rice can be grown successfully in Kaifeng. Suitable crop management practices such as direct seeding and increasing plant density can increase yield. Direct seeding also removes the need for maintaining standing water for about 20 days after transplanting (to overcome transplanting . shock), and thus reduces water input and increases water productivity.