WEST LAFAYETTE, Ind., Jan. 27 (UPI) -- The quality of water used to spray herbicides can affect their efficiency and crop producers should test water sources, U.S. researchers say.

Research by Purdue University found hard water or water with pH values as low as 4 or as high as 9 can lessen the efficacy of certain common plant herbicides.


"At this point, it seems to be specific to a limited number of compounds," professor of botany and plant pathology Bill Johnson said in a university release Friday.

"It's amazing how little we know about this topic, considering the number of acres of crops planted in Indiana each year."

Some common herbicides sensitive to spray water quality included glyphosate, nicosulfuron and saflufenacil, he said.

Saflufenacil, for example, was found to be less soluble at a low pH.

"It's similar to what happens when you put too much sugar in a glass of tea," he said. "The granules are then harder for plants to absorb."

And with spray water at a high pH, he said, the molecules in saflufenacil break apart and change the herbicide into a different compound altogether.

Testing spray water for pH and hardness is especially important if producers are getting water from multiple sources because levels can vary from well to well, he said.