Alabama grower adds to drip system

Central Alabama farmer Jay Minter has seen the future of Southeastern cotton production, and it's wet. That's why he has embarked on an ambitious project to install sub-surface drip irrigation on several hundred acres of prime cotton land. Minter, who already is running seven center pivots on 850 acres of cotton, experimented last year with drip irrigation on about 160 acres. This year, he's expanding his drip system to another 250 acres.

“I realized early on that the only way I'd be comfortable farming would be to irrigate,” says the Dallas County producer. “We gamble enough as it is in agriculture. I want to take as much risk out of the equation as possible. Irrigation helps to take the risk of drought out of farming.”

Irrigation — in its most basic form — is a risk management tool, says Minter. “I wouldn't farm without irrigation, so I look at it as just another cost of doing business. And, while pivot irrigation is a risk management tool, drip irrigation is more of a production management tool,” he says.

Sub-surface drip irrigation on row crops such as cotton is somewhat of a rarity in the Deep South, but Minter sees it as a good fit for some of his smaller fields.

“We had gone about as far as we could go economically with center pivots. So, in the fall of 2000, I traveled to Lubbock, Texas, to look at several farms where they were using drip systems. It appeared to be working for those growers, so I proceeded with plans to install my own system,” he says.

Minter's drip system is manufactured by Netafim, based in Fresno, Calif. It consists of 13-millimeter collapsible drip tape buried 14 inches deep under every other row, or every 76 inches. PVC pipe carries water from the source to pumps and filter stations. Each field is divided into zones and each zone has a valve to open or close water flow.

Some of the water will be pumped from 6-inch, 500-foot wells while other fields will be watered directly from the Alabama River. “When we really learn how to manage the drip system, it'll be a big improvement over our pivot irrigation. It might even pay us, at some point in the future, to get rid of some of the pivots and put in drip irrigation at certain locations.”

This past year, characterized as it was by plentiful rainfall, Minter used his initial drip system primarily as a means of applying fertilizer on cotton.

“In some fields, we put out all the nitrogen through the drip system. And even as wet as conditions were in 2001, we could pull up a plant at about the end of August and see that all of the feeder roots were growing toward the drip. Normally during a wet year, we'd expect to see the roots spreading out more.”

The system was used to water cotton once in late June, he adds. “We had to put out a fair amount of water to apply the fertilizer properly. By the time the fertilizer was applied — along with the water — the crop didn't require any more moisture. We even reached the point to where the ground was soaked, but we continued running the system just to apply the fertilizer.”

The drip system, he believes, allows a grower to apply fertilizer to the plant when it's most needed. “Either through preplant or early irrigation, we'll apply 40 units of nitrogen before first square. Then, from pinhead to first bloom, the cotton will get another 40 units of nitrogen. The first 40 will be done in one or two irrigation applications. The next 40 probably will be done on a weekly basis - 10 units per week for four weeks.

“After that, the cotton probably will get another 70 units from first bloom through peak bloom. The final nitrogen application probably will be done at least three times per week, with 6 units of nitrogen going out with each application. We're also applying all of our phosphorus and potassium through the drip. Putting out fertilizer through the drip system saves labor and is more effective in delivering nutrients to the plant's root system.”

Weekly petiole monitoring has proven the worth of applying fertilizer through the drip, says Minter. “When we used petiole monitoring on cotton that was watered by pivots, we could see spikes up and down whenever it needed foliar potash. The drip system takes out those spikes and applies the fertilizer when and where it's needed most.”

Drip irrigation also offers the potential for putting out other materials through the system, he says. In 2002, he'll apply Telone through the system for controlling root-knot and reniform nematodes.

“If you apply Telone through an injection method or with a ground rig, the rate will be 3 ounces per acres. At $12 per ounce, that's $36 per acre. But the rate with a drip system is 1 to 1 1/2 ounces per acre. That's a substantial savings.”

Drip systems also offer more flexibility in watering crops, says Minter. “With drip irrigation, we can meet all water needs of the cotton plant during the peak fruiting cycle. And, over the course of a season, we'll build up water in the system and use the soil as a ‘bank.’ If we don't receive rainfall, the plant can draw from this reserve.”

It's critical, he says, to have a “game plan” for irrigating cotton with the drip system.

“We combine several pieces of information to help us make the decision of when to begin watering. We look at the physiology of the plant, and at what time during the season it requires the most water. We also use pan evaporation to tell us how much moisture is leaving the soil. Then, we look at weather and humidity conditions, including expected rainfall. All of these factors together help us decide when to turn on the water.”

Minter buried his drip tape 14 inches deep with the hope of increasing its longevity. “The deeper we can put it into the ground, the longer it'll last. We shouldn't have a problem with breakdowns in the system. Our biggest risk will come from having poor filtration or from injecting some chemical or fertilizer that might damage or destroy the tape. Problems could be caused by anything, from sand to injecting a rate of Telone that would corrode the PVC pipe. The system will be flushed manually a couple of times during the year. However, the filters flush automatically on a more frequent basis. The pressure differential gauge tells the filter control when to flush itself.”

The drip system, says Minter, should pay for itself in four to five years, may be even sooner depending on cotton prices and weather conditions.

“The five center pivots I installed in 1999 paid for themselves during the 1999 and 2000 growing seasons. Our goal with all of this irrigation is to get our cotton production cost down to 40 cents per pound. I don't think we would ever make it with just center pivot irrigation. Hopefully, the drip systems will get us there. We need to be able to compete on the world market, or find another game to play.”

Minter has three pieces of advice for other farmers considering installing a drip irrigation system: 1) make sure the system is designed properly and installed according to the design; 2) don't skimp on filtration — poor filtration will reduce the life of the system; and 3) talk with other farmers who are using drip irrigation.

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