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Title: IS K THE CINDERELLA NUTRIENT FOR REDUCED TILLAGE SYSTEMS?

Author
item Karlen, Douglas
item Kovar, John

Submitted to: Fluid Fertilizer Foundation Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/15/2005
Publication Date: 2/15/2005
Citation: Karlen, D.L., Kovar, J.L. 2005. Is K the Cinderella nutrient for reduced tillage systems? [CD-ROM] In: Fluid Fertilizer Foundation Symposium Proceedings, Feb. 13-15, 2005, Scottsdale, Arizona.

Interpretive Summary:

Technical Abstract: Nitrogen (N) and phosphorus (P) have received an abundant amount of attention because of their well-documented potential for causing off-site effects if not managed properly. Has the increased attention on those nutrients resulted in an oversight regarding the importance of potassium (K), especially as the intensity of pre-plant tillage is reduced to cut energy costs, reduce soil erosion, and conserve or increase soil organic matter? Our objective is to review corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] response to various K fertilizer treatments applied to long-term (>30 yr) till-plant (ridge-tillage) and slot-plant (no-tillage) treatments on Clarion-Nicollet-Webster soils at the Iowa State University (ISU) Agronomy and Agricultural Engineering Research Center (AERC) located in Boone County, Iowa. A preliminary evaluation in 2003 and additional soil-testing in 2004 showed K stratification in the soil profile for the till- and slot-plant treatments. Whole-plant samples at the V6 growth stage in 2003 showed low K concentrations, but low rainfall during reproductive growth stages (grain-fill) mitigated or masked any yield response to post-emergence (V10) rescue applications of potassium thiosulfate (KTS). In 2004, 30 lb/acre broadcast, dry band, or liquid band applications were compared with a control (0 lb/ac K) for both crops. Use of sodium-saturated cation exchange membranes successfully quantified K movement and positional availability. All methods of providing additional K increased whole-plant (V6) and corn ear-leaf K concentrations as well as grain yield compared to the control. We conclude that K is being neglected and limiting yield when reduced tillage is used on these soils.