When was the last time you pulled a water sample on that water you fill the spray rig with? Do you have any idea what the pH is of the water you put in the spray tank? Most likely the well at “the shop” has a very different pH than the deep well for the center pivot. Why is all of this important?
The pH of your water carrier when spraying, affects the efficacy of the pesticide being applied. Did you know that according to Mississippi State Extension, the pesticide Paraquat, is not a stable pesticide at a pH of 8 or higher? How about Dicamba is unstable at a pH of 7.0 or higher, or Malathion is good for 8 days at a pH of 6 but is only good for 19 hours at a pH of 8?
According to Dr. Eric Prostko, UGA Extension Weed Specialist, Sicklepod control using Cadre 2AS drops by 7-10% when we move out of the pH range from 6-8. Palmer Amaranth (Pigweed) biomass reduction using Liberty, the percent is highest at a 4.0 pH drops slight at a 6.5 and has a significant drop by a 9.0. By not having the highest efficacy possible, we could be increasing the resistance amongst many of these common weeds.
A simple water test either using a pool kit or bringing a sample to your UGA Extension Office would tell you the pH of the water and if there are some adjustments needed. As always, if you have any questions stop by the Burke County Extension Office or call Cliff Collins at 706-554-2119 or email cliff.collins@uga.edu.