SIDNEY, Mont. – Irrigation water use will be especially important this year due to a mostly dry spring.
From 2017-2020, researchers from Montana State University’s Eastern Ag Research Center (EARC) conducted a four-year study looking at how pea yield is affected by irrigation.
“We tried to find out if too much irrigation at the wrong stage (with peas) could cause disease, or affect yield and/or protein percentage,” said Chengci Chen, MSU cropping systems agronomist and superintendent of EARC, at the MonDak Ag Research Summit.
With the first experiment, Chen worked with Bart Stevens, USDA ARS, on applying irrigation at three treatment stages: no irrigation (dryland farming); irrigation stopped early at flowering; and irrigation stopped late at pod filling.
In 2017, the greatest yield occurred when irrigation was stopped at the late stage, with yields about 4,125 pounds per acre.
Stopping irrigation early yielded around 3,378 pounds per acre, while no irrigation yielded about 3,000 pounds per acre.
In 2018, the greatest yield occurred when irrigation was stopped at the late stage, with yields about 3,380 pounds per acre. Stopping irrigation early yielded around 2,631 pounds per acre, while no irrigation yielded about the same as stopping irrigation early.
“In 2017 and 2018, we saw the same trend, with higher yields when irrigation was stopped later at pod filling,” he said.
In 2019, the greatest yield occurred when irrigation was stopped at the late stage, with yields halfway between 3,378 pounds per acre and 4,125 pounds. Stopping irrigation early yielded slightly less, while no irrigation yielded about 3,000 pounds per acre.
In 2020, all three treatments yielded about the same, at around 4,125 pounds per acre.
With the second experiment, Chen worked with Bill Franck, EARC research scientist, on the pea protein treatments.
Those treatments included: applying no irrigation or dryland farming; applying 1 inch irrigation at the vegetative stage; applying 2 inches of irrigation (1 inch at the vegetative stage and 1 inch at the flowering stage); and applying 4 inches of irrigation (1 inch at the vegetative stage, 1 inch at the flowering stage, and 2 inches at pod filling.)
“We wanted to find out which stage you should apply irrigation at and how irrigation would affect yield and protein,” Chen said.
With protein, similar trends among treatments were seen in 2018 and 2020.
“Interestingly, the highest protein in 2017 occurred when irrigation was stopped early (18 percent),” he said.
In 2017: early, 18 percent; late 17 percent; and no irrigation, 17 percent.
In 2019: early, 18; late, 18.5; and no irrigation was 15 percent protein.
“Without irrigation, protein was much lower in 2019,” Chen said.
In 2020: early, 19.5; late, 19.75; and no irrigation was 19 percent protein.
“It is good news that with irrigation you can produce both higher protein and higher grain yields,” he added. “With supplemental irrigation, protein did not increase with supplemental irrigation, but protein did not decrease either. You can produce consistent protein with supplemental irrigation.”