Testing field-moist soil samples improves the assessment of potassium needs by crops
Since 1989 and until the summer of this year, all soil testing laboratories in Iowa and the USA dried soil samples at 35 to 40 ºC (95 to 104 ºF) and ground them before analysis for potassium (K), phosphorus (P), and other nutrients. Since early fall, however, a laboratory that began operations in Iowa is using testing procedures that involve no soil sample drying, and another laboratory operating in Iowa and other states is offering moist soil testing in addition to the commonly used test based on dried samples. These laboratories are using a moist sample handling procedure that the Iowa State University (ISU) Soil and Plant Analysis Laboratory used and recommended from 1963 to 1988. The re-implementation of the moist test by these laboratories has generated many questions from Iowa farmers and crop consultants.