Hold the water: Expert says wait until cotton flowering stage to irrigate

Writer: Kay Ledbetter, 806-677-5608, skledbetter@ag.tamu.edu
Contact: Dr. Paul DeLaune, 940-552-9941, pbdelaune@ag.tamu.edu

CHILLICOTHE – Almost five years of data indicate producers can save as much as 40 percent of their water on a cotton crop by better timing their irrigation, according to a Texas A&M AgriLife Research scientist.

The bottom forefront shows irrigation after flowering compared to the top portion where early water promoted more plant growth but not necessarily greater yields. (Texas A&M AgriLife photo by Kay Ledbetter)

Dr. Paul DeLaune, an AgriLife Research environmental soil scientist at Vernon, has conducted long-term conservation tillage and irrigation studies at the AgriLife Research-Chillicothe station since 2008.

He discussed these studies during the Rolling Plains Summer  Field Day Aug. 30 in Chillicothe.

The tillage treatments included four treatments: conventional tillage, strip tillage, no-till and no-till with a terminated wheat cover crop. In the last five years, DeLaune also began looking at irrigation timing and amounts to determine: “Should we start watering soon after planting, or should we wait until a critical growth stage?”

He said with the growing concern over declining water resources and availability and competing water users, it is critical to determine the best time to apply that water, especially in areas of a declining aquifer.

The study compared early season irrigation, starting with 0.2 inch per day applied beginning after planting when the stand is established and continuing on, to waiting until the crop reached a critical growing stage – in this case flowering. The two treatments tested after flowering were 0.2 inch per day after flowering and 0.25 inch per day after.

These all provided a nice range of low, medium and high irrigation regimes, he said.

“What we’ve found over the last five years is the early irrigation, the banking of water, is not paying off and is a waste of water resources that has not shown up in improved yields or increased soil water profile,” DeLaune said.

He said Jim Bordovsky, AgriLife Research senior research scientist and engineer, Lubbock/Halfway, has observed similar results at Halfway and has conducted more extensive research dealing with irrigation rates and timings.

“On a four-year average, the high irrigation treatment has resulted in 27 percent more water use compared to the medium treatment and 42 percent more water use compared to the low treatment,” he said. “Yet, we have observed no statistical differences in lint yields among irrigation treatments, with yields within 10 percent of each other among treatments.”

Additionally, he said, they have noticed more water is conserved, and fields have higher irrigation water-use efficiencies under no-tillage and no-till with a cover crop regime.

“Our yields over a four-year average have been statistically higher for those no-till systems than both strip tillage and conventional tillage, at least 9 percent higher,” DeLaune said.

“So combining conservation tillage with proper irrigation management and timing can conserve water resources and improve your yields and economic returns.”

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