Water Smarts

May 29, 2009 02:15 PM

With water shortages afflicting numerous areas across the U.S., it makes sense to squeeze all the good from every drop. News outlets hammer stories nearly daily about depletion of the Ogallala Aquifer, for example, which waters eight states. Rural and urban residents alike need to change their relationship with water.

For many farmers that means modifying irrigation techniques. Paying closer attention to irrigation efficiency through better management can pay off in a big way. "Crop production is so system-oriented now; you've got to take care of every little thing. Make one little error and you can take a big yield hit,” says Danny Rogers, a Kansas State University (KSU) Extension ag engineer who works on irrigation.

You can minimize those errors by inspecting center pivot systems to make sure they fit your goals. "There are so many sprinkler package options. What's best depends on what you're trying to accomplish and the field conditions,” Rogers says.

"First, if the sprinkler package is designed for a certain flow rate and pressure, you've got to have that. For an efficient system, you have to ensure there's no runoff. When increased application rates are used, such as those that occur with in-canopy sprinklers and spray-type applicators, the soil can't soak it up fast enough. Runoff losses can be much greater than evaporative losses, so the nozzle package should be designed so no runoff occurs,” he says.

Start working on that by taking care of what Rogers calls "creeping maintenance” issues. Make sure your system runs the nozzles designed for it.

"Drop nozzles are a popular package. Equipment hits them. Animals hit them. They get dragged off. The farmer may grab whatever nozzle is in the back of the truck to replace the missing nozzle because any nozzle is better than an open outlet spraying like a garden hose. If you replace one or two on a system and do that for three or four years, you have a number of nozzles that are not the right size for that sprinkler package,” Rogers says.

"The irrigator needs to walk the system and make sure it is equipped with the right nozzles. If not, then replace the incorrect nozzles with the correct ones from the on-farm inventory or with a purchase from the dealer,” he says.

Several consultants in the area can now test center pivot systems using a simple in-field measuring device called the IrriGage, developed at KSU.

"Farmers hire consultants for fertilizer, for insects and for scheduling irrigation. This would also be a good way to use them,” Rogers says.

Irrigation timing is key to getting best use of water. Freddie Lamm, KSU research irrigation engineer at the Northwest Research Extension Center in Colby, Kan., says corn typically withstands presilking water stress better than postsilking stress, and modern hybrids tend to tolerate stress better than those of several years ago. Timing early season irrigation properly helps optimize the number of kernels per acre, a key factor in maximizing yield.

"Don't use the calendar or the center pivot ruts as your guide to cut off irrigation,” Lamm says.

"Continue to use day-to-day irrigation scheduling and anticipate how much water the plant will use in the last 30-day and 15-day periods. Plan out total water use so that water is used wisely, not wastefully. At the end of the season, making the right decision on irrigation is the cheapest input cost. You've already put all the seed, fertilizer, labor and previous irrigations in the ground,” Lamm says.

Lamm also recommends growers consider using consultants to map their irrigation strategy.

"If you want to stay in business, you have to employ more management,” he says. "This is not seat-of-the-pants farming. The best farmers are pretty sophisticated about irrigation.”

Fast Facts

  • One acre-inch of water equals 27,154 gal.
  • One ear of corn requires nearly 22 gal. of water to produce.
  • It takes about 1,400 gal. of water to produce a hamburger, french fries and
    a soft drink.
  • The total water requirement (combination of soil water, in-season irrigation and precipitation) for corn in western Kansas is about 24" per acre, with as much as 16" coming from irrigation.

You can e-mail Charles Johnson at cjohnson@farmjournal.com.

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