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Pivots over soybeans: run early, often

There's an oft-heard claim that farmers can't get the same yield results from a pivot on soybeans as they can using other forms of irrigation. Sterling Owens IV and his father, who farm in Tunica County, Miss., say they've found ways to get consistent results regardless of the irrigation method.

“Our system has become very dependable. We average about 60 bushels per acre regardless of the irrigation system used,” says Sterling, who spoke at the Tri-State Soybean Forum and Southern Soybean Conference held in Dumas, Ark., on Jan. 4.

The Owens split about 2,400 acres between cotton and soybeans. Their soybeans are about 80 percent irrigated with 700 acres under pivot and 250 acres border irrigated.

The key, says Sterling, is to know what the pivot is capable of. The main pivot puts out an inch of water every 4.5 days.

“From what I understand, peak water use of soybeans is about two-tenths to a quarter inch per day. So the pivot is barely getting the crop the water it needs. So, it's simple: if it doesn't rain, keep the pivot going. This drives some of our neighbors crazy. We have one neighbor who jokes that our pivot is like a NASCAR racecar. We stop it just long enough to fuel up and change the oil. With the kind of drought years we've had lately, that's pretty much true.

“People get mad at us because we have water standing in the turn rows. But that isn't what we're watering. I watch the forecasts and my father walks around our land with a spade checking the soil 6 inches deep.”

Another thing with pivot irrigation is how varieties react. The Owens have grown both Group 4s and Group 5s under pivots and done well with each. But in their experience, the Group 5s lagged 5 to 10 bushels behind the Group 4s.

“I asked (Mississippi Extension soybean specialist) Alan Blaine why that was the case one time. Off the top of his head he came up with an explanation. Since then, I've watched and his theory appears to be true. Under pivot, you're barely keeping up with demand. The last few years we've gotten very little summer rain. During the course of a season, something will go wrong, equipment will break, and there will be delays that bring on a bit of drought stress. It appears the Group 4s are able to handle those small stresses better than the Group 5s.”

The Owens planted all Group 4s last year. This worked out well because they have all their beans custom cut. There aren't a lot of Group 4s grown in their area, so it's been easy to get a custom cutter at that time.

“All things being equal, we come out with the same number of beans and we're out of the fields a month earlier.”

The Owenses shoot for planting dates of early April to mid-April. In 1998, they were part of the SMART program with Blaine telling them when to plant.

“We planted DPL 3478 on May 14 and came away with a touch over 55 bushels. From that experience I'm not afraid to plant a Group 4 anytime.”

With 19-inch rows, the very earliest Group 4s are where the Owens tend to have weed problems. “But on the type of ground we plant soybeans on, if we can get in, I can't see not planting on April 1. I can't see waiting a couple of weeks for a few inches height.”

On when to start and stop pivot irrigating, a rule of thumb Sterling has developed is this: “People should be laughing at us. This is particularly true with Group 4s. We get questions about whether we'll be watering while the combine is in the field.”

What about cost? While saying his figures aren't comprehensive, it appears it's been taking just under 1 gallon of diesel per acre to run the biggest pivot. Adding repairs, depreciation and things like that, “we're confident it ends up costing less than $3 per acre every time the pivot goes around.”

In the recent extremely bad drought years, the pivot has probably averaged about 10 trips, says Sterling. So it's almost $30 per acre spent irrigating.

“If we can irrigate how we want, we're getting just over 60 bushels per acre. If something goes a bit wrong with broken equipment or something, we get about 50 bushels per acre. Our dryland average is typically 30 bushels. So if you factor it out, we're getting about 30 bushels at about $1 per bushel investment. I think that's a pretty good deal and I don't see how we can afford not to continue.”


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