Drought Continues to Impact Nutrient Management Decisions

 

If dry soil conditions continue, soil samples taken this fall may provide misleading results for both potassium levels and pH, presenting an added challenge for producers. Potassium levels in soil tests have been shown to vary substantially under dry conditions. Soil pH measurements can be impacted because a dry season and poor plant growth mean much of the fertilizer added this spring and last fall remains in the 8-in. sampling zone in some fields. Higher-than-normal salt (fertilizer) levels affect the way the pH electrode functions and will produce a pH reading about 0.5 to 1.0 pH units lower than the actual pH. In addition, soil moisture has been insufficient for normal amounts of limestone reaction in soils limed this spring or last fall in Indiana, for example. Therefore, soil pH measured this fall will be lower than expected. The lime remains in the soil, however, and when moisture returns it will increase soil pH as expected. Purdue agronomists say re-testing this fall and adding more lime based on a low soil pH measurement may result in excessively high pH in future years.