Beware of Dry Conditions When Soil Sampling and Interpreting Test Results This Fall
Antonio Mallarino, Professor and Nutrient Management Extension Specialist, Department of Agronomy, Iowa State University
October 10, 2022
October began dry across most of Iowa except for some areas in southern and southeast Iowa, these conditions are allowing for rapid harvest progress. The outlook for the rest of the month calls for lower than normal rainfall. Below normal fall since August until the soil sampling time may result in lower than expected soil-test results for phosphorus (P), potassium (K), and pH. Therefore, farmers and crop consultants should interpret those soil-test results with caution.
Additionally, soil sampling with dry soils needs to be done carefully to avoid losing loose topsoil from the probe, which may result in even lower P and K values. This will be especially the case when sampling no-till fields or pastures because of the usual nutrient accumulation in the top few inches of soil. The correct 6-inch sampling depth also may be compromised with highly compacted or loose soil.