Rice Production: Good Reasons for Using Less Water

Arkansas produces approximately 50% of the nation’s 1 million plus hectares of annual rice production. Over 99% of this production is irrigated using flood irrigation with water drawn from underground aquifers. It is estimated that annual water withdraws for rice production are 5.3 million m³. These withdraws have resulted in significant aquifer depletion and large land areas being designated at critical ground water areas by the Arkansas Natural Resources Commission. A study was initiated in 2011 to determine if known water management options for rice production would be potential candidates for improving water management while providing additional benefits to the producers and industry. This study consisted of a standard flood treatment, two alternate wetting and drying (AWD) treatments, two row-watered (RR) treatments, and one combined AWD-flood treatment. Combined data for 2011 and 2012 showed an irrigation water use of 3392 m³ in the flooded treatment. Reductions in irrigation water use ranged from 52% in the AWD treatment that was dried to a 40% of soil water capacity between flooding events and 12% for the RR treatment dried to 60% of soil water capacity between water applications.  There were no significant differences in grain yields between the flood and AWD treatments and a significant reduction in grain yield in the RR treatments. Greenhouse gas emissions measured as yield scaled global warming potential ranged from 240 kg CO₂ Mg^-1 grain in the flooded treatment to 14 kg CO₂ Mg^-1 grain in the driest AWD treatment. Arsenic content in the grain decreased as the amount of time the field was flooded decreased. In total, these results show that rice production is possible with significant reductions in irrigation water use and that producers can accomplish this at the same time they reduce the environmental impact of rice production and obtain a better quality product.