Spraying should account for very little energy used on the farm, said Bill Casady, Extension agricultural engineer with the University of Missouri.

"Using about two-tenths of a gallon per acre, spraying is not an energy-intensive field operation," Casady said. "However, poorly managed spraying can lead to re-sprays, making spraying not only energy intensive, but economically very inefficient as well.

There are several potential obstacles to efficient application of crop protection materials, but the good news is that they all can be managed, he said.

Nearly as costly as a re-spray are the inefficiencies resulting from overlap, poor calibration and offtarget placement.

"Round these out with poor spray distribution or nozzle selection, and there potentially is a lot of room for improvement," Casady said. With little or no calibration, it is estimated that as few as 5 percent of spray events are within reasonable accuracy rates: the plus or minus 5 percent of optimum application.

"The surprising statistics from some research show that crop protection materials are often over-applied by more than 20 percent, due to overlapping and to poorly calibrated sprayers," Casady said.

A herbicide program with a projected material cost of $20 per acre may cost as much as an extra $4 per acre for the waste created by overlap. Similarly, a $50 program might cost an additional $10 per acre. Improving accuracy can save a potential $10,000 over a thousand acres.

A simple sprayer calibration can make huge differences, and it might even be worth investing in a light-bar for guiding sprayers through the field, Casady said. The least-expensive improvement is proper calibration, and the cost of calibration is almost free, and the returns are enormous.

"Calibration may very well be the best investment you ever make."

The perfect time to calibrate is while the sprayer is still clean at the beginning of the season. Start with a new set of nozzles if you covered a lot of acres last season, he said, and follow the calibration procedures found in MU publication G1270.

The chances are very high that without further calibration throughout the season, misapplication beyond the 5-percent margin is very likely. As nozzles wear, their output trends higher. Consider a re-calibration whenever you do a thorough sprayer cleanup. It doesn't need to require more than about 20 minutes.

For example, if that single re-calibration saves 5 percent on the last 500 acres sprayed at $25 per acre, then that 20 minutes worth of work would come in at about $1,875 per hour, according to Casady.

"Realistically, the actual savings for that 20-minute exercise are $625, and remember that any money saved is, as always, completely tax-free."

Casady urges growers and applicators to follow safe practices for limiting exposure whenever mixing, loading or applying crop protection materials. See MU publication G1917 for details.

SOURCE: March 17, 2006, article in University of Missouri's Integrated Pest & Crop Management newsletter.