Mississippi State University researchers and growers are changing how rice is irrigated to save groundwater and hold or improve yields. Under traditional flood systems, rice requires about 30–36 inches water annually, and in the Midsouth rice acres use a disproportionate share of the Mississippi River Valley Alluvial Aquifer, irrigation specialist Dave Spencer said. With rice markets tighter, growers and Extension specialists are testing ways to reduce pumping and costs without sacrificing yield.
Rice is typically drill-seeded, kept in upland conditions for several weeks, then flooded once seedlings are established and held with 2–4 inches of standing water through most of the season. MSU trials and other studies show rice does not require a continuous flood to reach commercial yields, prompting investigations of alternate wetting and drying (AWD) and other irrigation strategies.
In AWD, fields are not kept continuously flooded; water is allowed to fall below the surface before reflooding. MSU side-by-side trials tested standing floods, surface-level water, and regimes that let the water table drop as deep as 16 inches before reapplying water. Allowing the water table to fall that far caused measurable yield loss, but yields did not collapse, showing rice can tolerate intermittent dryness.
Alternate wetting and drying
The research found the best balance when soil water was not allowed to drop more than 4 inches below the surface. Managed that way, AWD maintained typical yields while cutting irrigation demand by 23–39% water saved, which translated to average on-farm savings of about $25 per acre. Lowering the depth needed for reflooding also lets growers capture rainfall events rather than constantly restarting pumps.
MSU has moved AWD toward automation to reduce labor and overpumping. A project led by Drew Gholson paired water-level sensors with actuated valves and pump controllers so fields are reflooded only when sensors indicate it is necessary and pumps shut off automatically when levels are reached. That system simplifies management and reduces operator time.
Automation delivered further gains in on-farm tests: automated AWD cut water use beyond manual AWD and provided yield benefits compared with a continuous flood. In MSU trials, employing automation with AWD reduced water use roughly 15% and produced a 4% yield gain relative to a continuous flood. The automated approach also lowers fuel and labor costs tied to pumping, offering growers a way to stretch groundwater and reduce per-acre production costs.
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