Herbicide carryover field research near Pullman, Wash.

Source: Washington State University Extension

Decreasing soil pH, also called soil acidification, is a growing concern in eastern Washington and northern Idaho. Researchers and farmers have measured soil pH values below 5.0 throughout the Palouse region, in particular.

Decreasing soil pH has serious implications for the cropping systems of the Palouse. A new publication in the Soil Acidification Series has been published. 

How Soil pH Affects the Activity and Persistence of Herbicides discusses how decreasing soil pH contributes to increased instances of herbicide persistence.

The publication categorizes commonly used herbicides as either a weak acid, weak base, cationic, nonionic polar, or nonpolar and briefly explains how the soil/herbicide interactions within each category can be affected by pH.

The Soil Acidification series begins with An Introduction, covering the fundamentals of soil pH and acidification, and continues with other fact sheets on more specific topics such as the influence of pH on pathogens and microbes, recommended varieties of specific crops, crop nutrition, and liming. Contact Drew Lyon for further information.