Re-evaluation of K Recommendations

The frequency of potassium (K) crop deficiency symptoms increased in Iowa during recent years. Preliminary on–farm research confirmed that corn and soybean yield responses sometimes were observed in fields that tested high according to soil-test K interpretations at the time. This early research also indicated that K placement methods for conservation tillage systems (such as no-till and ridge-till) probably were not the most effective. Therefore, an extensive research program was developed to re-evaluate Iowa K fertilizer recommendations. This effort included study of placement methods (including deep banding), soil-test calibration trials, and assessments of K removal with grain harvest. The research resulted in major changes to K recommendations that were introduced in 2003. These changes include an increase in the soil-test K level that should be maintained, a recommendation for occasional deep K placement for ridge-till and no-till systems, and an upward adjustment to K removal estimates. This talk will discuss this Iowa experience in a way that could be useful for improving K management in other regions.

Antonio Mallarino Professor of Agronomy
Iowa State University
apmallar@iastate.edu

Biography: Dr. Antonio Mallarino is Professor of Agronomy and soil scientist at Iowa State University (ISU). Since 1994 he has developed research and extension activities related to agronomic and environmental issues of soil fertility and nutrient management. Efforts have focused on improving the efficacy of phosphorus and potassium management by improving soil and plant tissue testing and fertilizer, manure placement methods for conservation tillage and use of precision agriculture technologies for nutrient management and by developing environmental phosphorus assessment tools. He has published more than 50 journal articles or book chapters and more than 150 technical and extension articles. Mallarino serves as chair the Advisory Committee of the Iowa State University Soil and Plant Analysis Laboratory, Associate Editor of Agronomy Journal, and Associate Editor of Soil Science Society of America Journal. He is member of the North-Central Regional Committee for Soil Testing and Plant Analysis (NCR-13), the committee Minimizing P Losses From Agriculture (SERA-17/IEG), and the oversight committee for the North American Proficiency Testing Program (S890). His expertise often is requested for by government or industry organizations that develop nutrient management guidelines.