With spraying season is just around the corner, Erdal Ozkan, Ohio State University ag engineer, reviews some common-sense ideas to get the most out of crop-protection products.
- Applying chemicals with a sprayer that is not calibrated and operated accurately could cause insufficient weed, insect or disease control, which can lead to reduced yields. Check the gallon-per-acre application rate of the sprayer. This can only be determined by a thorough calibration of the sprayer. Use clean water while calibrating to reduce the risk of contact with chemicals. Read OSU Extension Publication AEX-520 for an easy calibration method.
- How the chemical is deposited on the target is as important as the amount applied. Know what kind of nozzles are on your sprayer and whether or not their patterns need to be overlapped for complete coverage. "Make sure the nozzles are not partially clogged," Ozkan says. "Clogging will not only change the flow rate, it also changes the spray pattern. Never use a pin, knife or any other metal object to unclog nozzles."
- In addition to clogging, other issues, such as nozzle tips with different fan angles on the boom and uneven boom height, are the most common causes of non-uniform spray patterns. "They can all cause streaks of untreated areas that result in insufficient pest control and economic loss," Ozkan adds.
- Setting the proper boom height for a given nozzle spacing is extremely important in achieving proper overlapping. Conventional flat-fan nozzles require 30% to 50% overlapping of adjacent spray patterns. Check nozzle catalogs for specific recommendations for different nozzles.
- Know your actual travel speed and keep it as steady as possible. "Increasing the speed by 20% may let you cover the field quicker, but it also cuts the application rate by 20%," Ozkan says. "Similarly, a reduction of speed by 20% causes an overapplication of pesticide by 20% — an unnecessary waste of pesticides and money."
- Pay attention to spray pressure. Variations in pressure will cause changes in application rate, droplet size and spray pattern. "At very low pressures, the spray angle will be noticeably narrowed, causing insufficient overlap between nozzle patterns and streaks of untreated areas," he says. "High pressure will increase the number of drift-prone droplets."
- Don’t waste your chemical. After all, you have paid for it. "Spray drift wastes more chemicals than anything else," Ozkan says. "Don’t spray when the wind speed is likely to cause drift." Ozkan adds that you don’t want take the risk of getting sued by neighbors because of drift damage to their fields. Keep the spray pressure low if it's practical to do so, or replace conventional nozzles with low-drift nozzles. "Use other drift reduction strategies," he adds. "Keep the boom close to the target, use drift retardant adjuvants and spray in early morning and late afternoon when drift potential is less."
- Carry extra nozzles, washers, other spare parts and tools to repair simple problems quickly in the field.
- Calibrate your sprayer periodically during spraying season to keep it at peak performance. One calibration per season is never enough. For example, when switching fields, ground conditions (tilled, firm, grassy) will affect travel speed, which directly affects gallon-per-acre application rate.
- Read the chemical and equipment instructions and follow them. Wear protective clothing, rubber gloves and respirators when calibrating the sprayer, doing the actual spraying and cleaning the equipment.
