Spatial soil-K availability for no-till soybean [Glycine max (L.) Merr.] has not been studied extensively. We characterize soybean growth- and yield-component and quantify root parameters as a function of soil depth in K-stratified soils with 1 M ammonium acetate extractable-K ranges 60-290 at 0-10 cm increment and 50-90 mg kg-1 at the 10-20 cm increment. Shoots and roots (five depth increments to 50 cm) were collected during development and grain at harvest during 2 years. Soil K at or above the critical level (104 mg K kg-1) increased early-season leaf area and root K-uptake rates early and late in reproductive development. Greater number of seeds plant-1 increased yield for soils with K near the critical level. Soil-K above the critical level increased luxury K-uptake without improving yield, seed-K concentration and accumulation, or seed oil and protein concentration. Greater root length density (>41% of the total) in surface soil coupled with previous results showing greater water content throughout the season in surface soil compared to deeper layers illustrates K stratification caused by notill may enhance soybean K-uptake.
Bibliographical noteFunding Information:
Acknowledgements Funding for this project was provided by: the Mary S. Rice Farm Funds; Mosaic Co.; Potash Corp. 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 Inc.
- Growth and yield component analysis
- K distribution in shoot
- K stratification
- K uptake rate
- Root distribution in soil
- Soil-water and nutrient uptake relations