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Corn+Soybean Digest

Take Steps Now to Prepare Spray Equipment

It's a good time to get sprayers in shape for field use. Jim Wilson, South Dakota State University (SDSU) Extension pesticide applicator training /certification specialist, says doing a thorough inspection can save time and trouble in the field.

Start with a visual inspection. Replace any parts that show signs of wear. Thoroughly check screens and strainers to be sure they don't restrict flow. Double-check hoses to be sure that they are in good shape, especially if the unit is stored outside. Also be sure hoses are not running over sharp edges where they are prone to wear. "A failed hose may mean a chemical spill or at a minimum, substantial downtime," Wilson says.

Flush the system with water. Take the unit out of the farmyard to flush it, preferably into a field. But make sure any residue from last year's spraying is labeled for whatever crop you plan to grow in that field.

After flushing thoroughly, put clean water in the unit once more to inspect and calibrate the unit while it is in operation.

"Do a thorough calibration this spring before you do any spraying and recalibrate whenever making major rate changes, or replacing pumps, gauges, or nozzles," Wilson says. "Periodically spot-check your calibration by determining how much water and chemical you should have used on a field and compare it which what was actually used."

Start the sprayer and check the nozzle output and pattern to be sure you don't have plugged or worn nozzles.

A simple technique to evaluate output is to hold a cup under each spray nozzle for the same length of time, anywhere from 30 seconds to one minute. The level in the cup will allow you to see whether each nozzle is releasing spray at the same rate.

To evaluate spray pattern, it's sometimes helpful to drive forward with the sprayer in operation spraying clean water onto a surface such as gravel. By watching to see whether the surface dries uniformly, the operator can evaluate whether the unit is applying spray evenly.

Many newer sprayers have rate controllers which work very well when they're functioning properly. But Wilson says such units still need to be checked to see that flow monitors and other sensors are working properly. Since calibration methods vary with the manufacturer, refer to the owner's manual for proper procedures.

Improperly calibrated spraying equipment may cause reduced control or an excess use of a pesticide, both of which may be expensive. Spending a couple hours tuning up your sprayer may be time well spent.

Call SDSU Extension Pesticide Education Coordinator Jim Wilson with any questions. Reach him at (605) 688-4752, or

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