A combination of strip tillage and irrigation timing may improve water use efficiency and yield for Southwest cotton.
Conserving water is increasingly important for cotton farmers, says Diane Rowland, Texas AgriLife researcher in plant stress physiology in Uvalde. “Texas farmers have felt the devastating effects of drought, compounded by dwindling water resources,” she said during the Texas Plant Protection Association annual conference last December in College Station.
Rowland is studying methods to improve drought tolerance and water use efficiency in Texas cotton fields and to develop “field scale management tools to manipulate the physiology of the plant to make it more drought tolerant and increase yield.”
She said several factors are involved, including the plant’s physical endurance and its ability to recover following drought stress.
“Two Texas cotton production techniques – conservation tillage and primed acclimation – have shown promise for water savings while maintaining yield,” she said.
“Conservation tillage increases soil moisture, increases root growth and changes the plant’s water use pattern. Primed acclimation involves holding off water early and allowing the plant to develop root growth to become more tolerant later in the season.
“Combining the two techniques provided the best results,” in a 2009 test in Uvalde, Rowland said. It was a good year to test for drought tolerance. “The region experienced more than 60 days of triple digit temperatures and severe drought conditions that broke a 105-year record.”
Research included plots with a combination of tillage practices (conventional and strip) and water application (100 percent – full irrigation; 70 percent – deficit irrigation; and 70 percent to first flower and then 100 percent application for the rest of the growing season – primed acclimation).
“Despite the severe growing conditions, yields for the conservation tillage treatment were consistently greater than for the conventional tillage cotton,” she said. “The highest yields were found in the treatment that combined conservation tillage with primed acclimation.”
She said mechanisms responsible for yield benefits seem to be “related to soil moisture conditions, water use patterns, and stress tolerance in the crop.”
She also added ryegrass winter grazing to the Uvalde test under a quartered irrigation system with cotton, corn and sunflowers “to add economic benefits.”
She put in another test at Lubbock that included deficit irrigation and saw “similar results.”
She’s using monitors to measure water use. “Daily water use with strip till at Uvalde and Lubbock was significantly lower and the yield increased,” she said. “We are possibly increasing the endurance of the crop.”
She said bioassays used to measure recovery again show strip till has the advantage over conventional tillage. “We are improving the recovery of a crop with management techniques,” she said. “The combination of primed acclimation and strip till offers significant benefits. Primed acclimation may program the plant to turn on genes to respond to drought.”
Scheduling irrigation for primed acclimation, she said, may change from one year to the next. “Some years it may need 60 percent of full irrigation and some years it may need 80 percent. We need to monitor crop stress to make certain. But we need enough stress to get those genes turned on.”
She said the number of hours a crop is exposed to temperatures above the stress threshold may be as important as the temperature. “A significant time above the temperature line affects the crop. Also, some irrigation events are more effective than others.”
She’s making more detailed measurements of crop stress with a SmartCrop program.
“We need two more years of research at Uvalde to develop recommendations,” Rowland said.
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