ARS | Publication request: Potassium Uptake Efficiency and Dynamics in the Rhizosphere of Maize, Wheat, and Sugar Beet Evaluated with a Mechanistic Model

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 28, 2009
Publication Date: January 23, 2010
Citation: Samal, D., Kovar, J.L., Steingrobe, B., Sadana, U.S., Bhadoria, P.S., Claassen, N. 2010. Potassium Uptake Efficiency and Dynamics in the Rhizosphere of Maize, Wheat, and Sugar Beet Evaluated with a Mechanistic Model. Plant and Soil Journal. 332:105-121.

Interpretive Summary: Recent price increases of fertilizers have focused attention on nutient-use efficiency. One measure of nutrient-use efficiency is uptake efficiency, which varies greatly among different plant species. With a controlled-climate experiment, we evaluated potassium (K) uptake efficiency of corn, wheat, and sugar beet grown on a low-K soil. We found that sugar beet and wheat were more efficient than corn in acquiring K from soil. Wheat tended to produce a larger root system relative to the plant, and sugar beet roots absorbed K at a relatively faster rate. From calculations with a nutrient uptake model, we learned that length and density of root hairs produced by the three species also played an important role in plant K efficiency. The results of this research will benefit both commercial growers and the fertilizer industry by providing nutrient management information that leads to optimum crop utilization and minimizes potential nutrient losses.

Technical Abstract: Plant species differ in nutrient uptake efficiency. With a pot experiment, we evaluated potassium (K) uptake efficiency of maize (Zea mays L.), wheat (Triticum aestivum L.), and sugar beet (Beta vulgaris L.) grown on a low-K soil. Sugar beet and wheat maintained higher shoot K concentrations, indicating higher K uptake efficiency. Wheat acquired more K because of a greater root length to shoot dry weight ratio. Sugar beet accumulated more shoot K as a result of a 3- to 4-fold higher K influx as compared to wheat and maize, respectively. Nutrient uptake model NST 3.0 closely predicted K influx when 250 mg K kg-1 were added to the soil, but under-predicted K influx under low K supply. Sensitivity analysis showed that increasing soil solution K concentration (CLi) by a factor of 1.6 to 3.5 or buffer power (b) 10- to 50-fold resulted in 100% prediction of K influx. When both maximum influx (Imax) and b were increased by a factor of 2.5 in maize and wheat and 25 in sugar beet, the model could predict measured K influx 100%. In general, the changes affected K influx of root hairs, demonstrating their important role in plant K efficiency.