Iowa State University (ISU) potassium (K) soil-test interpretations and fertilizer recommendations were updated in November 2002. These recommendations are contained in publication A General Guide for Crop Nutrient and Limestone Recommendations in Iowa (PM 1688), which is available at through any Iowa State University Extension office or at http://www.extension.iastate.edu/pubs. Major changes included new soil-test K interpretations for all crops and K fertilizer placement recommendations for corn and soybeans grown with no-till and ridge-till systems.
Iowa State University
Mallarino, Antonio P. and Sawyer, John E., "Use new potassium soil test and fertilizer recommendations" (2003). Integrated Crop Management News. 1688.
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