Rice Water Use Efficiency and Yield under Continuous and Intermittent Irrigation

In the Brazilian state of Rio Grande do Sul, rice (Oryza sativa L.) is predominantly grown using continuous flood irrigation, which requires large quantities of fresh water. Due to increasing scarcity and demand for water, modern agricultural systems need to produce more food with less water. The objective of this study was to evaluate the effect of different irrigation management systems on water use efficiency, quantity of water loss due to runoff, and rice grain yield. The experiments were conducted from 2007 through 2010 at an experimental station of the Plant Protection Department of the Universidade Federal de Santa Maria, Rio Grande do Sul state, Brazil, on an Albaqualf sandy‐loam soil. Treatments consisted of two irrigation management systems: continuous flooding (CF) at approximately a 10‐cm flood depth and intermittent irrigation (II) where the flood was allowed to fully subside before being re‐established to a 10‐cm depth. Intermittent irrigation increased storage of rainwater by reducing runoff water by 56% compared with CF. In addition, II reduced irrigation water use by 22 to 76% resulting in a 15 to 346% increase in water use efficiency (WUE). Rice yield was not affected by II compared with CF. Intermittent irrigation provides greater water conservation, does not reduce rice yield compared with CF, and improves the WUE of rice.