We know that during a dry summer applying water to Mid-South crops will increase potential yields. The key to making money on those irrigated acres, however, may be knowing when the best time is to begin irrigation efforts.

"The goal of irrigation is to prevent crop stress throughout the growing season. Many producers, though, start late, quit too soon, and have poor field drainage," irrigation specialist Earl Vories told growers attending the Delta Irrigation Workshop Nov. 9 in Delhi, La.

Vories, an Extension agricultural engineer at the University of Arkansas, recommends growers consider all of the variables involved in irrigation scheduling before deciding when to turn on the water.

Many variables - including drainage, rainfall, soil type, irrigation method, pumping capacity, and commitment - are unique to each farming operation. "Are you committed to properly irrigating or is it something you're not going to think about until you have everything else done?" he asks.

To make the job of deciding when to turn the pumps on easier, irrigation specialists in Arkansas have developed a computer irrigation scheduling program. The program uses the water balance approach, which Vories sees as most practical for the Mid-South area.

Phil Tacker, Extension agricultural engineer at the University of Arkansas in Little Rock, Ark., says the scheduler program can be incorporated easily into various crop production systems. "We've tried to make the data entry as straight-forward and quick as possible," he says.

To schedule irrigation applications using the software, a producer simply supplies the program with basic information for each crop field. The required information includes a field name, planting date, emergence date and type of irrigation system being used.

Then throughout the growing season, daily rainfall and temperature data is added by the producer to the program. At that point, the computer program takes over, identifying the dates when each crop field is in need of watering.

"When you are scheduling your irrigation, the soil may look very moist on top, causing you to think you're watering too much. However, that moisture may only go down a few inches in the soil. Proper irrigation should result in a depth of 12 inches of soil moisture," says Joe Henggeler, an agricultural engineer with the University of Missouri Delta Center in Portageville, Mo.

According to Henggeler, irrigation costs in the Missouri Bootheel averaged $15 per acre in 1999. Breaking it down, fuel costs averaged $12 per acre, and well maintenance and repair averaged just over $3 per acre.

"The biggest cost by far is the initial cost of adding irrigation capabilities, which we estimate averages between $50 and $75 per acre," says Henggeler. "So, it's not a good idea to have such a big investment and then not use it."

The Arkansas irrigation scheduling program can be downloaded free from the internet. To access the program, go to www.uaex.edu on the Internet and select agriculture from the left of the page. Then, from the table in the center of the page select agricultural engineering under the heading for agriculture and natural resources. That will pull up another web page, at which point the irrigation program can be found in the programs box on the left side of the page.