Pay close attention to sprayer maintenance to get the most out of your investment in pesticides this season, says Erdal Ozkan, ag engineer with Ohio State University Extension. He offers the following tips for improving sprayer performance:
Calibrate. Applying chemicals with a sprayer that is not calibrated and/or operated accurately could cause insufficient weed, insect or disease control and reduce yields. Check the sprayer’s gallon/acre application rate by doing a thorough calibration. Use clean water while calibrating to reduce the risk of contact with chemicals. Learn more about sprayer calibration.
Mind the nozzle. How the chemical is deposited on the target is as important as the amount applied. Know what kind of nozzles are on the sprayer and whether patterns need to be overlapped for complete coverage. Make sure the nozzles are not partially clogged. Clogging will change flow rate and spray pattern. Never use a pin, knife or any other metal object to unclog nozzles.
Avoid streaks. In addition to clogging, other factors 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. All cause streaks of untreated areas that result in insufficient pest control and economic loss.
Check the boom. Setting the proper boom height for a given nozzle spacing is extremely important in achieving proper overlapping. Conventional flat-fan nozzles require 30-50% overlapping of adjacent spray patterns. Check catalogs for specific recommendations for different nozzles.
Keep travel speed as steady as possible. Increasing the speed by 20% may let you cover the field more quickly, but it also cuts the application rate by 20%. Similarly, a 20% speed reduction causes a 20% over-application of pesticide – 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. High pressure will increase the number of drift-prone droplets.
Avoid drift. Spray drift wastes more chemicals than anything else. Don’t spray when the wind speed is likely to cause drift. Don’t take the risk of getting sued by your neighbors because of drift damage to their fields. Keep spray pressure low if practical, or replace conventional nozzles with low-drift nozzles. Other drift-reduction strategies include keeping the boom close to the target, using drift-retardant adjuvants and spraying in early morning and late afternoon when drift potential is less.
Be prepared. Carry extra nozzles, washers, other spare parts and tools to repair simple problems quickly in the field.
Calibrate again. 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/acre application rate.
Be safe. Follow chemical and equipment instructions. Wear protective clothing, rubber gloves and respirators when calibrating the sprayer, doing the actual spraying and cleaning the equipment.