If every soybean grower in the delta region of Mississippi could eliminate just one irrigation during the season, it could halt the overdraft of the aquifer that has been occurring in recent years — plus saving money, labor, and time, says Jason Krutz.

And he said at the Mississippi Agricultural Consultants Association at their annual meeting that preliminary research data indicate this could be done prior to soybeans’ R-3 growth stage without adversely affecting yield.

(Editor's note: Dr. Krutz and Dr. Darrin Dodds, assistant Extension professor at Mississippi State University, will present a special Irrigation Technology Seminar at the Mid-South Farm and Gin Show Friday, March 1, at 1:15 p.m. on the mezzanine level of the Cook Convention Center.)

“We’ve run the mathematics on it, and eliminating one irrigation would pretty much take care of the overdraft on the aquifer,” he says.

Aside from the water conservation aspects, says the associate Extension and research professor at the Delta Research and Extension Center, Stoneville, Miss., growers are concerned about increasing regulations on withdrawal of water from the aquifer in the years ahead.

“Right now, there are proposals on various tables suggesting that 10 percent to 20 percent of our existing irrigation wells could have meters put on them, and as early as 2015 that data could be provided to regulatory agencies for monitoring.

“Producers are concerned that there will be restrictions on water use in the future. Consequently, Mississippi State University research and Extension personnel are being proactive in developing systems that can maintain or improve yield and profitability, if permitted values are strictly enforced — 18 inches per year for corn, cotton, and soybeans, and 36 inches per year for rice.”

Krutz, who assumed his position last May, says the Mississippi Soybean Promotion board is funding the research to determine if there is a stage in soybean development when water stress can be tolerated without having an adverse effect on yield.

Studies were done last year, he says, using different irrigation initiation and termination times, “trying to identify periods during the growing season when we could potentially stress the soybean plants without having an adverse impact on yield.”

Several different irrigation scenarios were used for comparison against a standard.

Eliminating two irrigations at the R-3 growth stage resulted in a 10 percent yield loss, Krutz says, and eliminating three irrigations from R-3 to R-5 resulted in an 18 percent to 20 percent yield loss.

“But the data suggest there is a zone where we could potentially stress soybeans — perhaps all the way through R-2 — and not have an adverse yield effect. From R-3 on, however, we saw that if we put stress on the plants we were going to get a serious adverse yield effect.”

Using a scientific irrigation scheduling tool and stressing the plants through R-2, then initiating irrigation at R-3, only four irrigations were applied, but yields were equivalent to the six irrigation standard treatment.

“We’re hoping this year to have studies at 10 to 12 locations to see if these results hold up and if we can reliably eliminate irrigation through R-2 without yield loss,” Krutz says.

With the increasing use of irrigation in the Delta, he says, most growers could benefit from the use of an irrigation scheduling tool.

“I’ve asked a lot of producers, with acreages ranging from 1,000 to 16,000, how many irrigation sets they have during a season, how many fields they irrigate, and how they keep track of those irrigations. Probably 95 percent can’t tell me how many irrigation sets they have.

“In today’s technology-driven agriculture, we’re generating data galore and zapping it everywhere electronically — yet when it comes to tracking irrigation and water use, in many cases we’re still in the Stone Age.”

Irrigation scheduling tools

Producers need to know how many irrigation sets they make in a season, and have some way to keep track of that information, Krutz says. “It’s just part of basic management, and there are tools available to do this. They range from simple to complex; some are inexpensive or free, some are expensive.”

After discussing the issue with producers and consultants, he says, “We’ve developed a simple tool at Mississippi State University that can help with this.

“Basically, it’s a simple chart that’s available in three formats — one can go on a shop wall, one in a pickup truck, and one on the desktop. It makes it easy to keep up with when irrigations are initiated, and when they need to be continued; it’s just uncomplicated basic recordkeeping.”

In other areas of the U.S. where producers have used an irrigation scheduling tool, no matter which kind, they’ve had water savings of as much as 35 percent, compared to a neighbor not using a scheduling tool.

“That’s a huge savings in terms of the water we’re using now in Mississippi,” Krutz says.

In recent meetings, he says, “I’ve been talking growers about evapotranspiration values, how much water crops actually use, and ways to calculate this. Many of them have said, ‘Well, if there was something on the Web to do this, I think I would be more inclined to use it.’

“We’re moving in that direction, and before the crop season arrives, we hope to have something available. We’ll have an interactive map — click on your county, there’ll be a drop-down for cotton and soybeans, and you can see the ET value for your county for each week. If you know your soil capacity, and when you’ve had rain, you can easily calculate whether you need to irrigate.”

A tool that has been available for some time and is a proven water saver, Krutz says, is the PHAUCET program that was developed in Arkansas.

“With 80 percent of the Delta furrow irrigated, if we could get every acre on PHAUCET, that alone would pretty much make up for the existing aquifer overdraft of 300,000 acre feet per year.”

Simply using a more effective polypipe layout can result in water savings of 20 percent on regular-shaped fields, he says. “Additionally, we’ve seen a 20 percent to 25 percent savings on fuel and on time spent managing irrigation. Whether you’re using electricity, diesel, or gas, with today’s costs, think about putting that 20 percent to 25 percent savings in your pocket. With PHAUCET, you should be able to shave at least 25 percent off the time it takes you to get water across a field.”

On irregular-shaped fields, he says, the water savings from using PHAUCET can be even greater, as much as 30 percent to 50 percent, with additional savings on fuel and labor. “This is something we’re going to continue to push,” Krutz says.

Other studies this year will include evaluation of surge irrigation. “Literature from the western states indicates we might be able to cut water use by 50 percent on some soil types,” he says. “We haven’t done a lot of research on surge in Mississippi, and we want to see what kind of potential it may offer.

“I know one producer who has set up his entire farm on surge and PHAUCET, and has realized tremendous water and fuel savings. We’re going to look at surge on different soil types and different crops to determine if it could have potential for some of our producers.

“For the last few years, we’ve also been evaluating various in-field management practices to improve furrow irrigation,” Krutz says. “For the last couple of years, using furrow dike systems in both soybeans and cotton, we were able to apply 25 percent less water and still maintain yield potential.”