Irrigators across much of the U.S. have moved to center-pivot sprinkler irrigation during the past 25 years, but corn and soybean growers in the Mississippi Delta have found that tweaking surface irrigation with a trio of best-management practices (BMP) allows them a cost-effective way to maintain yields and conserve water and energy.
A significant move since 2000 to flexible polypiping affords many Delta growers a relatively inexpensive method to distribute water from shallow wells. This allows them to tap the Mississippi Alluvial Aquifer without the maintenance and fixed costs of center-pivot sprinklers.
Dave Spencer, Mississippi State University (MSU) graduate student involved in irrigation efficiency studies, says three technologies have helped farmers save significant pumping energy and applied water and bump yields, as indicated from a four-year side-by-side study of more than 20 cooperator farms in the Delta.
Spencer says the demonstrations included 20 paired fields with cooperators irrigating according to their normal practices, and MSU irrigating adjacent fields using polypiping systems. The MSU systems were designed for computerized pulse characteristics and surge valves, along with in-field soil moisture monitors to aid in irrigation timing decisions. The trials ran from 2013 to 2015, with two sites compared in 2016.
LESS THIRSTY. “The results of combining better irrigation timing through moisture monitor readings and more efficient water infiltration through the use of pulse irrigation and polypipe systems specifically designed for each field showed an overall 42% decrease in total water applied in the BMP fields--including wet and dry years,” Spencer explains. After four years, the BMP fields showed a 5-bushel-per-acre corn yield increase across the whole study.”
“We know furrow irrigation is not as efficient as overhead sprinklers, but we’re trying to optimize the system in use in the Delta to conserve water and maintain profitable farming operations,” he says.
Results from the widespread study on cooperator farms in Arkansas and Mississippi have caused a significant move by area growers to adopt the BMPs, Spencer adds. Because of varying soil conditions and field elevations, he says it’s necessary to design each field’s irrigation system according to a survey of the field.
“Using NRCS’s [Natural Resources Conservation Service] PHAUCET (Pipe Hole and Universal Crown Evaluation Tool) program or Pipe Planner, software provided by Delta Plastics--the provider of much of the polypiping used in the Mid-South--a grower can design a poly system based on water availability and pump pressure, field grade and soil type,” Spencer explains. “The free programs allow growers to plug in their field dimensions and pumping capacities to design a set of irrigation runs--to take maximum advantage of the water they have.
“The programs tell you how long irrigation sets should be and the size of holes used to apply the correct amount of water along that run,” he continues. Pulsed irrigation through the use of surge valves allows computer-controlled timing of irrigation sets to prevent flooding one area of a field while leaving other rows water deficient.
“The third BMP that is vital to water conservation is improving irrigation timing through the use of in-field soil moisture monitors that provide a guide to moisture conditions at 6, 12, 24 and 36 inches in the root zone,” Spencer says. Growers tend to overwater unless they know for certain the roots in the growing zone have sufficient water, he adds. “Many producers find they can save at least one watering per season just because they know their crops aren’t stressed for moisture.”
PERSONAL EXPERIENCE. Noel Cumbaa, who irrigates 2,600 acres of corn and soybeans near Panther Burn, Mississippi, is one of those growers.
“We’d been using polypipe and land leveling since the mid-1990s, but for a long time, we’d just roll out the pipe and punch holes, and it was evident we didn’t know what we were doing,” Cumbaa says. “Our irrigation timing was based on, ‘If the crop is wilting, you water.’ ”
The first year as a cooperator in the MSU study, Cumbaa watched as the MSU fields yielded roughly the same as his fields but with one less watering cycle. That showed him the value of knowing soil moisture and timing irrigation to meet its needs. “Today, using soil moisture monitors, we save money by waiting to pump until the crop needs it and stopping the pumps at the end of the season when we know the crop is cutting out,” Cumbaa says.
He saves one watering per crop per season. At $2.50 per gallon for the price of diesel, that amounts to a $3 to $4 savings per acre. He uses the computerized pulse irrigation system and field-specific polypiping sets, along with soil moisture monitors. His yields have remained roughly the same, but his water use is much more efficient. “The surge valves really benefit us on the sandy loam soils, where water runs out of the field quickly. By surging, we allow the water to infiltrate in a ‘soak cycle’ for a more even application through the field.”
Many of Cumbaa’s irrigation runs are 12 to 16 hours, and he’d have to be out changing water at 6 a.m. or 8 p.m. “With surge valves set on a 24-hour timer, the system waters both 12-row sets automatically, which saves me time and labor,” he says.
REMOVE FRUSTRATION. Nearby, near Rolling Fork, Clark Carter also made the changes after studying the results of the MSU BMP trials.
“The biggest thing it did for us, besides cutting water use, was it ended the frustration of trying to design our own polypipe systems,” Carter recalls. “We tried to run water 2,000 feet, and by the time we put enough pressure on the pipe to move the water that far, we’d blow out the pipe. We had no idea of how to size the holes or the fact we were trying to move water too far.”
Carter is a believer in the popular PHAUCET system and says he will be adopting the Pipe Planner system in the future. “With the proper size holes and irrigation sets of reasonable length, we now water our fields without flooding parts of them and leaving the upper ends bone dry,” he explains. “The surge valves have worked well, and we have very little runoff. They are certainly a water saver.”
Like Cumbaa, Carter is impressed with his Watermark soil moisture monitors. He has placed 35 monitors on his 4,000 acres of furrow-irrigated corn and soybeans.
Carter recalls a recent corn crop that, on many acres, required no irrigation and on others, only one watering was necessary.
“In the old days, we’d have watered that corn four times,” he says. “We were into what I call recreational irrigation. If it was Monday, we were irrigating.”
Those days are gone. Carter says he drives his pickup to the turnrow standpipe where his moisture monitor leads are housed, rolls down the window and hooks up the leads to his monitor meter, and he knows immediately if and when he needs to irrigate.
Irrigation Planning Software:
> PHAUCET (Pipe Hole and Universal Crown Evaluation Tool) is a free computer software application. It was designed by engineers with the Natural Resources Conservation Service to calculate existing irrigation-system performance and define alternatives for improving irrigation efficiency. For more information, visit www.uaex.edu/environment-nature/water/irrigation.aspx.
> Pipe Planner is a free software package available through Delta Plastics of the South LLC. For more information, visit www.pipeplanner.com.
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