Growth and magnesium uptake of tall fescue lines at high and low potassium levels¹

Cooperative research between USDA, ARS, Soil‐Plant Interaction Research Unit and Alabama Agricultural Experiment Station, Auburn University, AL 36849.

Abstract

Five tall fescue (Festuca arundinacea Schreb.) clonal lines with diverse root and xylem diameters were grown in nutrient solutions with magnesium (Mg) concentrations of 42, 125 and 250 μM and potassium K concentrations of 133 and 333 μM. Leaf Mg concentrations increased with increasing Mg rates at both low and high K concentrations. The tall fescue line with the largest root and xylem diameters had low leaf Mg concentrations, indicating a possible increased Mg tetany potential when consumed by cattle. The response of the K/(Mg+Ca) ratio in the plant, an indicator of tetany potential, to varying solution Mg at low and high K was determined for each of the five lines. No Mg effects or interactions were significant. Line, K, and line x K effects were all significant for the K/(Mg+Ca) ratios. The line with the largest root and xylem diameters had the highest tetany potential (highest cation ratio). Higher solution K gave higher K/(Mg+Ca) ratios.

Key words:

• Root diameter
• xylem diameter
• nutrient concentration
• relative grovth rate
• nutrient solution
• mineral nutrition
• Festuca arundinacea

Notes

Cooperative research between USDA, ARS, Soil‐Plant Interaction Research Unit and Alabama Agricultural Experiment Station, Auburn University, AL 36849.

Soil Scientist, USDA‐ARS‐Soil‐Plant Interaction Research Unit, Assistant Professor, Agronomy and Soils Department, Auburn University.