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Ltd Irrigation: 'Flowers Fit Well into Drought-Hit Rotations

Friday, January 3, 2003
filed under: Irrigation/Water Use

It’s hard to find silver linings in the drought that has plagued much of the High Plains in recent years—and especially in 2002. But one of the few has to be the experiences of producers who have inserted sunflower into a limited-irrigation plan, either in combination with or instead of corn.

For a number of them—particularly those whose wells could not keep up with the needs of a full circle of corn—the result has been good sunflower yields and still-respectable corn crops.

Bruce Unruh and Barry Hinkhouse, both of whom farm near Burlington, Colo., are two producers who reacted to the drought and some lower-producing wells by plugging in more sunflower acres under their center pivots.

How dry were they in 2002? Unruh says his farm received 1.5” of rainfall in September of 2001—and no other precipitation during the entire winter. Through mid-September 2002, his rainfall amounts totaled perhaps 4.5”. So in an already semi-arid locale whose annual precipitation averages 16 to 17”, that's 10” below normal.

Hinkhouse, who irrigates about one-third of his cropland, faced similar conditions. Actually, he points out, the Burlington area entered its fourth year of drought as of August ‘02. August of 1999 was dry, reducing yields of what had been a promising corn crop. “In 2000 we had no (dryland) fields make under 20 bushels; but the top was 45 bushels. In 2001 we harvested a handful of (dryland corn) fields that made 15 bushels; the rest were not worth combining. Then, in 2002, our dryland corn crop was pretty well done by the end of June,” Hinkhouse relates.

Dryland fields weren’t the only ones suffering in 2002. Unless a well was capable of delivering 750 to 850 gallons of water per minute, irrigated corn also suffered. Hinkhouse, whose well capacities range from 150 to 850 gpm, says he tore up some irrigated corn fields last year on which the center pivots had run continuously throughout much of the spring and summer.

The lower-end wells simply could not provide enough water to overcome the extreme rates of evapo-transpiration generated by the heat and drought. Unruh watered one circle of corn continuously last summer from a 650-gallon well, but still ended up with a poor yield. “Too much heat,” he summarizes.

So where and how does limited-irrigation sunflower fit into this picture? For Barry Hinkhouse, there are four basic irrigation scenarios. Sunflower fits prominently into three of them.

First, with a high-producing well (800 to 850 gallons/minute), he sticks strictly with corn and doesn't even consider planting sunflower on that field. A well of that capacity should be able to meet the corn crop’s water needs regardless of rainfall levels.

Second, there’s the case of a 240-acre field with two circles, one corn and one sunflower, being fed from a 400- or 500-gallon well. Hinkhouse expects the corn (old sunflower) ground to be very dry, so he’ll apply 8 to 10” of water either in the fall after the ‘flower harvest or in early spring. At least another 8”, be it in the form of irrigation water or natural precipitation, are needed on both circles during the March-May period.

With a 500-gpm well, applying 8” across 240 acres will take about two and a half months, he indicates; so if it’s a bone-dry winter, that means the center pivots will be running for most of the March-May period. He cites the year when he had three locations with the above situation. In one case, Hinkhouse pre-watered both the corn and sunflower. Prior to bud stage, he cut the water to the corn on one of the fields and applied 2” to the ‘flowers. On adjacent corn/sunflower acreage, he simply left the water on the corn. In both cases, the flowers yielded identically, but the corn yield where he removed the water in order to irrigate the sunflower was 20 to 25 bushels below the yield of the other corn. The third scenario for Barry Hinkhouse would be a single center-pivot (120 acres) fed by a 250- to 350-gpm well. He¹ll plant half of the circle to corn and half to sunflower, having prewatered the entire field (8 to 10”). But again, once he’s into the prime period (mid-June to the end of August), he wants as much of that water going to the corn as possible. So he’ll set his center pivot to run slowly across the corn half; then speed it up to move as rapidly as possible across the 60 acres of sunflower. Once it returns to the corn ground, it again slows down. Hinkhouse calculates he’s applying only about 0.07” of water on the ‘flowers during each pass.

The fourth scenario is one Hinkhouse has not yet faced, but may in the future. That’s where the well capacity is less than 200 gallons per minute. “If I was under 200 gallons, I’d probably just raise ‘flowers and wheat,” he says. A corn/sunflower split might work, depending on rainfall levels, but would be risky, he suggests.

Bruce Unruh worked with a range of confection sunflower situations in 2002: from dryland fields to limited irrigation to ‘flowers under full irrigation. His full-irrigation sunflower, fed by a 400-gpm well, was prewatered in May with about 3”, planted in early June, and then watered throughout most of July and August.

These ‘flowers showed no stress and ended up yielding an impressive 2,000 pounds per acre. For Unruh, one limited-irrigation program consists of a prewater application of about 4”, after which the center pivot is taken off and not turned back on the confections until prebud stage. A 1.5” application at that time is all the ‘flowers receive until postbloom, when he applies another 1.5” and stops.

In 2002, Unruh had another confection sunflower field where his entire irrigation program consisted of the prewatering prior to planting. Supplemented by just a single inch of rainfall in August, the field yielded about 450 pounds per acre. Corn under that 650-gpm circle was watered consistently during its growing season, but still showed significant stress.

Not surprisingly, Unruh’s ‘02 dryland ‘flowers were generally very poor. (About 80% of his overall crop acreage is dryland.) The best field was no-tilled behind corn; others went in on no-till wheat ground. He didn’t even bother to harvest a couple of the fields. Though he didn’t split fields (half corn, half sunflower) under a single center pivot in 2002, Unruh anticipates doing so in 2003. Also, on one of his lower-producing wells where two center pivots have in the past irrigated corn and sunflower, he expects to drop the corn and go strictly with ‘flowers. “I think I can end up netting more dollars with two circles of ‘flowers rather than one corn and one sunflower,” he indicates.

Unruh plans to cut back on his corn acreage this coming season and go with more sunflower (precisely because of the drought conditions and his own limited-capacity wells. Lower overall input costs for sunflower also factor into his decision.

“I wish I had done it this past year,” he adds. “But I was an optimist. I thought we’d have more rainfall. ‘Flowers respond a lot better to limited irrigation,” this eastern Colorado producer affirms. “If you pull (irrigation water) off corn at the wrong time, it’s done. With sunflower, even if you pull off the water and they don’t get rain, they¹ll hang on longer.” – Don Lilleboe
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