Arkansas irrigates 4.5 million to 5 million acres annually. “And we do it a lot of different ways,” said Phil Tacker, the state Extension irrigation specialist.
“For irrigated acres, we rank fourth in the nation behind Nebraska, California and Texas,” said Tacker, who spoke at the Soil and Water Conservation Conference at Arkansas State University in Jonesboro, Ark. “We're one of the few states to increase irrigated acres recently. That's encouraging. We can take up some of the slack for areas that are no longer able to irrigate. The crops those areas have lost need to be grown somewhere.”
To everyone's benefit
Not all the news is good, though. A bit over 90 percent of Arkansas' irrigation comes from groundwater.
Tacker pointed to a photo of a gushing well pipe. “If we had this problem around the state, we wouldn't have to worry about a lack of water. This is a well in early March near a river in Crittenden County. Unfortunately, this isn't what's seen everywhere.
“It's to everyone's advantage — farmers and industry — to try and conserve our water and get the most benefits out of every inch we put out. There are some things we can do to help accomplish that. The list I'm going over isn't comprehensive, but it does hit on some key practices.”
Tacker's normal approach is do more than just talk. He prefers to be on farms with growers and landowners, trying to find solutions — “looking in the toolbox — for current problems while knowing more must be done in the future.”
Producers have challenges even getting water to the root zone — whether from irrigation or rainfall.
“The ground will seal up and crust over. The intake rate changes through the season. The first water down the row goes well, but subsequent irrigations don't penetrate as much.
“We've got to do what we can to keep the soil mellow and fluffed up so water can soak in. Tillage is a big part of that with trying to keep stubble on the surface or close to it to help with water retention.”
Sometimes, he said, producers need to “open the ground back up” when the root zone and water-holding capacities are too restricted.
In terms of water capture and re-use, it doesn't take a lot to get started.
“A tailwater recovery with a re-lift pump can be great for supplementing irrigation. On-farm storage structures provide water and help reduce sediment and turbidity.”
Tacker said “most folks who have precision graded say their operations are improved: levees are straighten, surveying isn't as difficult, and water management is easier.”
The newest twist to grading — zero grade — isn't yet on many state acres. With zero grade, rice producers have a chance to save water because they're able to control a shallow, uniform flood.
“The jury is out on what happens in such a field when growing a crop other than rice. With rice, there's not as much worry about pulling the flood off quickly.”
The multiple inlet approach — using underground pipe and risers to put water onto a field at set intervals — is becoming more popular.
“Used to be, one riser in a field was thought to be adequate. Now, more producers are saying, ‘Putting another eighth of a mile of pipe down and putting in another riser make things more convenient and reduce runoff.’
“Producers don't use underground pipe in every case. Some use polypipe to pump water down the side of a field and dump it in.”
Researchers have collected much data from demonstrations using the system. “We take a multiple-inlet field beside a conventional field and keep up with the water that is placed on them.”
In 1999-2002, Tacker and colleagues had 15 sets of data for comparisons. The data fields ranged from northeast to southeast Arkansas and had soils from sandy loams to clays. Production fields involved weren't uniform.
“We had fields that were flat, fields that were steep, fields on hills.”
The data show that (by using the multiple inlet), “we saved about 26 percent of irrigation water — on average, about 10 inches of water. Last year, we didn't save that much. But, as everyone knows, we had more rainfall, so there wasn't as much need for pumping anyway.”
Another benefit of this system is labor savings. “We weren't looking for it, but it appears there are possible yield advantages to multiple-inlet. That may have something to do with a cold water injury reduction.”
The Phaucet computer program was developed by the NRCS in Missouri. “It tells a producer — after information is entered — what size hole to punch in the tubing, what pressure will be on the tubing and how best to fit the system to a given field.
“Producers can have fields anywhere from a quarter mile length of row (tapering) to 700 feet towards the end.
“Punching holes can be guesswork. When do you start punching a different size hole? Would you be better off going every other middle? Phaucet is a handy program to help evaluate and answer those questions.”
However, Tacker cautions that most producers find it difficult to take the program off the shelf and start using it effectively.
“Starting off, producers usually need a little guidance with it. But Phaucet is something we're going to support more… because it does have the potential to help reduce water usage.”
Tacker shows a typical chart that Phaucet generates. “In this case, the field went from a 1,200-foot furrow to 800 feet. The program told the producer that at 600 feet to switch from a ¾-inch hole to 11/16 inch. That's the kind of thing it does well.”
Surge irrigation has caught on in Missouri. “In fact, it's so popular that producers there can get help — cost-share — in purchasing a surge valve. Sending sheets of water across the field, surge can help get water across quicker and more uniformly than conventional furrow irrigation.”
If a producer wants to stay flat-planted in a field that lies in one direction, border irrigation is something to consider.
“With good figuring and management, you can stop the water when it's about three-quarters of the way down. Then you can start on the next set of borders and let the bottom of the set you just left fill out. There's less waste that way, unlike with furrow where you have to water all the way to the bottom before soaking begins.”
Arkansas has “quite a few” center pivots working — particularly on cotton and corn. It's a great way of irrigating, said Tacker, but there are times when it's difficult to get water to soak into the soil.
“Some Mississippi folks have tried something that we need to consider. They've put a narrow slot in every other middle — maybe an inch wide and 6 inches deep. The slots tend to stay open through the year and allow water to soak in better rather than run to low spots. The slots don't seem too intensive and yet help a lot with water penetration.”
Drip irrigation has been around a long time with vegetable farming and landscaping. The last few years, though, “we've looked at it with some row crops — cotton particularly. Typically, we're using a sub-surface drip, developed in the arid West.”
The biggest thing with drip irrigation is the hefty initial investment.
“That's the first hurdle. But it does have the potential to precisely apply water and nutrients. And not putting anything on the surface means less runoff and erosion. However, we have some things in Arkansas that others don't have to deal with.
“Most of our water has iron and high pH and that can lead to plugged pipes. So there are some precautions.”
Some farmers are beginning to use irrigation pump monitors that have recently become available. Attached to the discharge of wells they contain, “sensors that look for the presence or absence of water. The system also has a transmitter so that if water quits flowing, it will call you on your cell phone or drop an e-mail to let you know ‘Well number so-and-so has quit flowing.’”
Once alerted, a producer can check to see what's wrong. “On farms with 30, 40 or 50 irrigation wells scattered around, that's a huge labor saving.”
e-mail: [email protected]