The Big Sandy Mountaineer -

Bare Patches in Chouteau County fields may be attributed to low pH soils

For a few years, Chouteau County producers have found bare patches in their wheat and barley fields. Patches seem to be located in water logged areas of the field, respectively. In addition, patches seem to be expanding from year to year. The problem may be low pH or high acidity in the upper 6 inches of soil. Below are a few questions and answers I have compiled from a peer reviewed article out of Washington State University Extension.

• What is pH? PH is a measure of the concentration of hydrogen ions in a system. For each whole number step down on the pH scale there are ten times more hydrogen ions, or acidity, than the previous step. Neutral pH is 7, while the neutral pH range is generally between 6 and 8. Alkaline or high pH values are above 8, while acidic or low pH conditions are typically considered to be below 6.

• How does low pH soil affect crop production? Reduced availability of certain nutrients resulting from low pH affects the growth and development of crops and weeds. Pesticides may be less effective and persist longer in low pH soil. Low pH can negatively impact the soil microbial community. Lastly, Low pH can favor fungal pathogens and certain weed species.

• Why is aluminum toxicity in plants a major problem with low pH soils? Low pH can degrade clay minerals in the soil containing aluminum releasing aluminum and promoting toxicity.

• What are the symptoms of aluminum toxicity? Symptoms include yellowing, stunting, and reduced plant vigor. Aluminum toxicity symptoms are most prominent in early growth stages.

• Why do we have low pH in Chouteau County? Use of nitrogen-based fertilizers has accelerated the rate of soil acidification on agricultural lands. Ammonium in nitrogen fertilizers is converted to nitrate by soil microbes producing acidity. • What are strategies for reducing the rate of soil acidification and restoring health to low pH soils?

1. Leave crop residues in the field to help buffer pH changes.

2. Use crop rotations that incorporate legumes. Legumes do not require supplemental nitrogen fertilizers.

3. Use alternative nitrogen fertilizers. Unfortunately, non-acidifying fertilizers, such as calcium nitrate, are not commonly used because they are not economically competitive, compared to commonly used ammonia based fertilizers.

4. Apply lime.

5. Implement practices that optimize nitrogen use efficiency in the cropping system.

Information for this article comes from Washington State University Extension. The article is called Soil pH and implications for soil management: an introduction, FS170E. Authors include Carol R. McFarland, Crop and Soil Sciences, Washington State University, David R. Huggins, USDA-ARS, and Richard T. Koenig, Associate Dean and Director of Extension, Washington State University. The article is available online. A hard copy of the article can be mailed upon request. The Chouteau County Extension office phone number is 622-3751.

Montana State University U.S. Department of Agriculture and Montana Counties Cooperating. MSU Extension is an equal opportunity/affirmative action provider of educational outreach.