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AgCenter researchers are seeking irrigation alternatives to conventional delayed flooding (seen here) that use less water. LSU AgCenter photo.
With the volume of rainfall Louisiana has received over the course of 2021, rice producers may be forgiven if irrigation practices aren’t top of mind.
However, researchers must think both in the short and long term, so LSU AgCenter soil fertility specialist Manoch Kongchum is studying if large yields can be achieved with less water.
Kongchum is in the midst of a four-year study at the H. Rouse Caffey Rice Research Station that is examining water use and grain yield from four different water management practices: conventional delayed flooding, alternate wetting and drying, semiaerobic, and furrow irrigation, which is also known as row rice.
“Conventional delayed flooding is what most farmers do now,” Kongchum said. “We are trying to find more options if we can to reduce the water use, and that’s the idea of the grant.”
The study, which began in 2017, registered significantly less usage of irrigation water in 2017 and 2019, which saw 31.7 and 41.7 inches of rainfall, respectively, during those years’ growing seasons. The semiaerobic water management practice had the lowest water consumption, reducing water by 37% to 67% over delayed flooding, according to Kongchum. The alternate wetting and drying method reduced water usage by 10% to 50%. Furrow irrigation used more water than alternate wetting and drying because tailwater — water that runs off into the lower end of a field — wasn’t retained as much.
“In my trials, we didn’t see much water conservation with furrow irrigation because there was not enough tailwater saved.” Kongchum said. “By keeping the tailwater in their farms, growers could significantly reduce the amount of water use.”
Kongchum said that even though grain yield in the alternate wetting and drying management practice was not much different than that of delayed flooding, the practice hasn’t gained popularity in Louisiana as compared to furrow irrigation.
“Alternate wetting and drying is an insurable practice in the United States,” Kongchum said. “For this practice, water should be held the first three weeks after flooding to maximize nitrogen fertilizer efficiency. After that period, water can be allowed to go down until a certain predetermined irrigation trigger point is reached.”
Kongchum said water availability, land preparation and crop rotation patterns all come into play when deciding which water management practice works best in what setting.
“The research is important to understand how to use water and how much producers can save by using less while getting more benefits,” Kongchum said. “Short-term solutions today could affect farming for years to come.”
