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Title: IS POTASSIUM LIMITING NO-TILL CORN YIELDS?

Author
item Karlen, Douglas
item Kovar, John

Submitted to: Proceedings of Great Plains Soil Fertility Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/7/2006
Publication Date: 3/7/2006
Citation: Karlen, D.L., Kovar, J.L. 2006. Is potassium limiting no-till corn yields? Proceedings of Great Plains Soil Fertility Conference. 11:206-211.

Interpretive Summary:

Technical Abstract: Potassium (K) was thought to be a limiting factor for no-till and ridge-till corn (Zea mays L.) and soybean (Glycine max L. Merr.) in a long-term tillage and crop rotation study at the Iowa State University (ISU) Agronomy and Agricultural Engineering Research Center (AERC). Our objective in this study was to compare 30 lb K2O/A broadcast, dry subsurface band or liquid surface band applications with a control (0 lb/A). The treatments were applied to the same plots each year for two years, thus providing three site-years of response data for corn and one for soybean. Pre-treatment soil-test status, plant nutrient concentrations and yield were monitored. Sodium-saturated cation exchange membranes also were used to monitor positional availability of the K from the four treatments. Soil-test data confirmed K stratification after several years of reduced tillage, and that K saturation was less than 2% for both the continuous corn and rotated blocks. Although not always statistically significant, whole plant and leaf tissue K concentrations were always lower in check plots compared to those receiving K, and the concentrations for most samples were below the level considered sufficient for the various plant parts. Sodium-saturated exchange membranes were useful tools for characterizing the positional bioavailability of the K following K application. Check-plot yields were significantly lower than those in plots receiving K, except for broadcast treatments on the rotated block, although the response to K was still positive. In 2005, a 16% yield penalty for continuous corn was also observed. Overall, this study confirms that K is a limiting nutrient at this site, and that more attention must be given to K management, especially if corn residues are to be harvested for biofuels production in the future.