Yield and water use of irrigated tropical aerobic rice, systems

Increasing water scarcity necessitates the development of irrigated rice systems that require less water than traditional flooded rice. In irrigated aerobic rice systems, rice grows in nonflooded and nonsaturated soil under supplemental irrigation. The development of such systems should start with the identification of promising varieties and the quantification of yield potential, water use, field water outflows, and water productivity. In this paper, we report on the results of growing different tropical upland and lowland rice varieties under irrigated aerobic conditions during six seasons in 2001-2003 at the International Rice Research Institute in the Philippines. The highest yields under aerobic conditions were realized in the dry season with the improved upland variety Apo (5.7 t ha(-1)) and the lowland hybrid rice Magat (6 t ha(-1)). These high yields were obtained in relatively wet soil with seasonal-average soil moisture tensions in the root zone of 1012 kPa and with maximum values of around 40 kPa. On average, the mean yield of all varieties was 32% lower under aerobic conditions than under flooded conditions in the dry,season and 22% lower in the wet season. Total water input was 1240-1880 mm in flooded fields and 790-1430 mm in aerobic fields. On average, aerobic fields used 190 mm less water in land preparation, and had 250-300 mm less seepage and percolation, 80 mm less evaporation, and 25 mm less transpiration than flooded fields. Without plastic sheets to prevent seepage in flooded fields, the water productivity of rice (with respect to rainfall and irrigation water input) under aerobic conditions was 32-88% higher than under flooded conditions. We conclude that the concept of aerobic rice holds promise for farmers that do not have access to enough water to grow flooded lowland rice. More research is needed into the development of improved varieties, the optimization of crop and water management, and the sustainability of aerobic rice under continuous cropping. (c) 2004 Elsevier B.V. All rights reserved.