Potassium- (K) and water-stratification in conservation tillage, rain-fed agroecosystems may reduce soybean [Glycine max (L.) Merr.] performance. A split-pot experiment with two soil-K levels [80 mg Kg-1 (Low-K) and 164 mg Kg-1 (Optimum-K)] and two soil-water contents [insufficient (Dry): variable between 55 to 85% field capacity (FC); sufficient (Wet): constant at 85 to 95% FC] was imposed to determine the effect of synchronous and asynchronous availability of localized K and soil water on soybean roots, nutrient uptake, and shoot growth. Asynchrony of soil water and K had no impact on soybean dry matter accumulation or nutrient uptake. Optimum soil K levels were relatively more important than soil water content to increase K availability and K tissue concentration and accumulation. Shoot- and root-growth responded more to water- than to K-stress. Shoot-K accumulation increased concomitantly with sufficient water availability and greater root surface area (RSA), but RSA was more important relative to water for K accumulation. Optimum-K with sufficient-water increased K accumulation by 50% compared to the insufficient-water treatment. Since enhanced K uptake occurred with greater RSA, and roots proliferated in response to water availability and not localized K, K should be placed in the soil fraction that provides sufficient water availability.
Bibliographical noteFunding Information:
Acknowledgements Funding for this project was graciously provided by: the Mary S. Rice Farm Funds; Mosaic Company; Potash Corporation of Saskatchewan; International Plant Nutrition Institute-FAR; and United Soybean Board. In-kind support for a portion of the samples analyzed was provided by A&L Great Lakes Laboratories Incorporated.
- K stratification
- K uptake rate
- Root distribution
- Root response to localized K and water
- Soil exchangeable K
- Soil water availability, soil solution phase-K
- Split root system