Spray Water Quality: An Overlooked Factor in Herbicide Performance
Applied Research
Eric Yu
Farmington
Abstract
Water makes up more than 95% of most herbicide spray solutions, yet its quality is often overlooked when preparing applications. Factors such as mineral content and pH can influence herbicide performance. Minerals commonly found in groundwater, including calcium, magnesium, and iron, may interfere with certain herbicides and reduce their effectiveness. In addition, highly alkaline water can cause some herbicides to break down more quickly before reaching target weeds. Although products are available to adjust spray water pH, questions remain about how much they improve weed control under field conditions. A field study conducted in 2025 near Rochester, Minnesota evaluated whether adjusting spray water pH could improve control of waterhemp, a common and difficult-to-manage weed in corn. The study tested a water-conditioning product (AlpHa Shot) used with a standard corn herbicide program. The product was added either several days before spraying or on the same day as the herbicide application to determine whether timing affected performance. Including the water conditioner in the spray solution improved waterhemp control compared with treatments that did not adjust spray water. Early-season control increased by about 10%, and season-long control remained 7% higher. Plots treated with the water conditioner also had 64% fewer waterhemp plants and 55% less weed biomass by the end of the season. The timing of the water conditioner did not influence these results. These findings highlight the importance of spray water quality in herbicide performance. Adjusting spray water pH under alkaline conditions may improve weed control and reduce late-season weed pressure, providing a simple and low-cost step to enhance herbicide effectiveness.
Poster has NOT been presented at any previous NACAA AM/PIC
This poster is being submitted for judging. It will be displayed at the AM/PIC if not selected as a State winner. The abstract will be published in the proceedings.
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Authors: Eric Yu, Ryan Miller
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Yu, E. Extension Educator, University of Minnesota Extension, Minnesota, 55024
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Miller, R. Extension Educator, University of Minnesota Extension, Minnesota, 55901