Scheduling rice irrigation using soil moisture thresholds for furrow irrigation and intermittent flooding

Abstract

Alternative methods of rice (Oryza sativa L.) irrigation are gaining increasing popularity across the U.S. Mid-South, but an allowable soil moisture deficit stress has not been defined. This study was conducted in 2018 and 2019 to determine the soil moisture threshold for furrow-irrigated rice (FIR) and alternate wetting and drying (AWD) rice production systems to minimize irrigation water use while maximizing grain and milling yield. Soil moisture thresholds of −15, −30, and −45 kPa, as determined by Watermark sensors at a 10-cm depth in the top third of the field, were compared with conventional flood rice (CFR) on a Calloway silt loam and a Sharkey clay in eastern Arkansas. Soil moisture threshold had no effect on grain or milling yield across irrigation thresholds; however, the bottom third of FIR, where a flood was held, consistently produced higher grain yield (10,652–10,965 kg ha−1) than the top third (9,442–9,722 kg ha−1). Significant differences in irrigation water use efficiency (IWUE) were achieved under AWD and FIR. The IWUE did not differ across AWD irrigation thresholds but was 58.1–103.8% greater than that of CFR. The −15 and −30 kPa FIR thresholds did not improve IWUE, but using a −45 kPa irrigation threshold resulted in a 42.7% greater IWUE than CFR and 66.0% greater than the −15 kPa threshold. Results suggest that using a −45 kPa irrigation threshold at the 10-cm depth can potentially maintain grain and milling yield while increasing IWUE under AWD and FIR.