18 and 36. Those two numbers are likely to take on increasing significance in the months ahead as farmers, farm organization leaders and regulatory officials continue to grapple with the problem of a declining alluvial aquifer beneath the Mississippi Delta.
Those are the maximum amounts of irrigation water growers can apply – 18 inches for cotton, corn, soybeans and grain sorghum and 36 inches for rice – under the irrigation well permits granted them by the Mississippi Department of Environmental Quality.
“I remember asking last year how many acre inches we can apply to corn, cotton and soybeans, and none of us knew,” says Jason Krutz, irrigation specialist with Mississippi State University and a speaker at the Mississippi Delta Irrigation Summit held at Stoneville, Miss., Dec. 10. “That number is 18, and rice is 36.”
Krutz said few producers have probably looked for that number and few cared until now even though the amounts are specified on the well permits.
“But at the end of this season, 10 percent of those wells will be metered, and the information will be given to a regulatory agency,” he said. “So somebody cares now about how much water we’re pumping out of the aquifer."
For now, participation in the metering program is voluntary and will remain so as long as growers using the meters report their information for 2014 and enough additional growers sign up in 2015 to reach the 10 percent level. But presentations at the Summit indicated a number of growers are exceeding the 18- and 36-inch maximums on their permits.
On the other hand, if the metering program doesn’t reach 10 percent participation by the June 30, 2015 deadline and the 2014 metering information isn’t reported by the Feb. 15, 2015, deadline, MDEQ officials have said the program could become mandatory.
Chris Wells, the MDEQ’s chief of staff who was pinch hitting for Gary Rickard, executive director of the agency, noted that latest estimates say farmers in the Mississippi Delta can pump up to 1.5 billion gallons of day during peak irrigation use.
”It’s an astronomical number,” he said. “I personally can’t fathom that much water, and you can imagine the impact is that over several decades there has been a decline in the levels in the aquifer and not enough recharge during winter to replace all of that.”
Wells said that’s what the Delta Sustainable Water Resources Task Force, which was created by the Department of Environmental Quality and consists of a number of farm and governmental organizations is charged with addressing.
The Mississippi Delta Irrigation Summit, which was attended by nearly 200 producers from Mississippi and Arkansas, is also part of that effort, he noted.
Krutz said he believes farmers have charged Mississippi State University with the task of making them better furrow irrigators. “That charges makes sense with 80 percent of our acres being furrow irrigated, and we need to make strides in improving how we deliver water with that system.”
Mississippi State specialists have settled on three tools they believe will help growers make better use of their furrow irrigation systems. Those are software programs like Pipe Planner, surge irrigation and using soil moisture sensors for irrigation scheduling.
“What we did on all our Extension sites and what we’re encouraging our producers to do is use Pipe Planner,” says Krutz. “It is well-based, free, fairly interactive, and it gives you a lot of information. It will tell you what size and type of polytubing you need and it will tell you the size, quantity and spacing of the holes you need to make sure all the water will hit the tail ditch at the same time which then improves our application efficiency.
“And, by default, it’s going to reduce our irrigation costs.” (Pipe Planner is a software program developed by Delta Plastics Inc., a Little Rock, Ark.-based company that provides disposable plastic tubing for irrigation. Delta Plastics is providing the software free as part of its new H2O Initiative.)
Surge irrigation, he said, “takes care of problems we have in conventional irrigation. We can have a lot of tail water runoff, which is inefficient, and what we can’t see is that we can have a lot of deep percolation loss with water moving below the rooting zone, which means the plant cannot utilize it.”
It can be especially beneficial in silt loam soils or the traditional cotton soils, which tend to “seal over” when water hits them, Krutz noted. Sending “pulses” of water across the field so that it has time to soak in before another pulse pushes down the row improves irrigation efficiency about 25 percent.
Growers can choose from a number of soil moisture sensors that all do the same thing: “They’re going to tell you when the profile is full and how much water is being utilized in the different regions of the root zone, and they can set a threshold at which point we think we will have yield loss or demonstrate a yield loss if we go beyond that,” he said.
“That’s a long ways off from just scheduling every Monday when we start turning the wells on. We’ll see when we go into our different field locations where we’ve paired up with you if this tool actually works.”
Krutz’s comments seemed to be well-received by attendees, for the most part. One grower was slightly skeptical.
“Jason has been working in relatively wet conditions the last two years,” said one producer. “We’re waiting to see how this works when we go weeks without rainfall, and the crops are begging for moisture.”
For more information on conserving irrigation water, visit http://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/national/wntsc/?cid=nrcs143_023638