Moisture On Command

May 15, 2009 02:08 PM

What is one of the primary factors that prevent farmers in the heart of the Corn Belt from raising 300 bu. per acre corn? Water. More precisely, the timing of when plants get water.

Farmers in western Kansas and Nebraska often harvest 300 bu. per acre corn simply because their dry climate and light soils require irrigation. Relying on irrigation allows them to provide optimum moisture to their crop at just the right times.

Farmers in parts of the country where Mother Nature provides moisture haphazardly know thirsty crops will fall short of their potential. The notion that they are not doing all they can to maximize yields has spurred a growing interest in irrigation among farmers, says Mark Stumpenhorst of Hook's Point Irrigation in Stratford, Iowa.

"In central Iowa, guys have been getting 200 bu. corn even if they get a little dry in July or August,” Stumpenhorst says. "They're assuming that they're getting the highest yields possible. Irrigation might bump those 200 bu. yields up to 250 bu. simply by never allowing the corn to feel stress from lack of moisture.”

Even though drought is infrequent in north-central Iowa, pockets of sandy soil undermine Steve Prohaska's yields every summer. After careful analysis, he invested in a
center pivot irrigation system in 2002. Meticulous record keeping has proven it to be a sound investment.

"On the farm where I have a center pivot irrigation rig, for the four years prior to installing the rig I averaged 158.5 bu. per acre,” says Prohaska, who farms near Garner, Iowa. "With irrigation I've averaged 211.25 bu. per acre. I'm averaging almost 53 bu. better, simply by being able to provide moisture when my crop needs it.”

A little water makes a big difference.
Prohaska puts on an average of 3.5" of water a year. "I water at night to reduce evaporation and only put on ½" to ¾" [of water] at a time,” he says. "My records indicate that with $4 corn I need 34 extra bushels per acre to cover my irrigation costs. With $5 corn I only need 28 extra bushels. I've been averaging more than 50 extra bushels, so irrigation makes me money.”

The only stumbling block to irrigating where irrigation isn't a tradition is water availability. A center pivot irrigation rig that spans 160 acres can gulp 900 gal. to 1,000 gal. of water per minute. Few farm ponds can supply adequate water. Wells are preferred, but some areas of the Midwest have difficulty tapping high-capacity aquifers.

"My well is 380' deep, and that's close to the limit of being cost-effective,” Prohaska says. "I had it calculated that if we didn't hit adequate water by 400', irrigation wasn't going to work for me.”

Steve Bitner of Central Illinois Irrigation in Havana, Ill., says local well drillers should know the location and capacity of regional aquifers. Bitner says some farmers find ample water at only 100', while others can't drill deep enough to find an aquifer adequate to feed an irrigation rig.

"The depth of a well affects the price of the initial investment as well as the cost of running the rig,” Bitner says.

"In general, the average irrigation system around here, including a well, costs around $800 per acre. Break that down over the 20- or 30-year lifespan of a rig, and you're looking at $26 to $27 per acre [per year] cost, against an annual increase in yield of 50 or more bushels. Irrigation pencils out pretty good.”

Neil Parr of Mason City, Ill., had to drill only a 200' well to find adequate water to supply his 1,300' center pivot, which covers 160 acres. This past year was the first year that he decided to irrigate.

"It was a wet year, and I only ran it a little in June to test it, some more in July to sidedress 28% nitrogen and then I put on half an inch every week in August,” Parr says. "Corn on my unirrigated ground right beside it topped out at 175 bu. per acre. My irrigated corn yielded 247 bu. acre.

"I should've installed irrigation 20 years ago,” he says.

You can e-mail Dan Anderson at

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