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ARS Home » Research » Publications at this Location » Publication #193998


item Karlen, Douglas
item Kovar, John

Submitted to: Fluid Journal
Publication Type: Trade Journal
Publication Acceptance Date: 8/10/2005
Publication Date: 10/1/2005
Citation: Karlen, D.L., Kovar, J.L. 2005. Is K the Cinderella nutrient for reduced-till systems? Fluid Journal. 13(4):8-11.

Interpretive Summary: Nitrogen (N) and phosphorus (P) have received much attention because of their well-documented potential for causing problems with water quality. The increased attention paid to these nutrients has resulted in less attention being paid to the importance of potassium (K) in crop production in central Iowa. In a reduced-tillage field experiment, we found that K fertilizer (30 lb/acre) broadcast, banded near the row, or applied as a liquid on the soil surface increased whole-plant K content early in the growing season, leaf K concentrations later in the season, and final grain yield, compared to plots in which no K fertilizer was applied. We conclude that K fertility is being neglected and limiting yield when reduced tillage is used on these soils. Potassium fertilization is an inexpensive and environmental-friendly way to promote maximum soil productivity, which will certainly benefit those involved in corn and soybean production.

Technical Abstract: 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 postemergence (V10) rescue applications of potassium thiosulfate (KTS). In 2004, 30-lb/A broadcast, dry band, or liquid band applications were compared with a control (0 lb/A K) for both corn and soybeans. 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-till is used on these soils.