Physiological differences among populations of Anthoxanthum ordoratum L. collected from the Park Grass experiment, Rothamsted. IV. Response to potassium and magnesium.
In pot experiments, populations of Anthoxanthum odoratum collected from acid soils (both natural and Park Grass), which had not been fertilized with K, responded to K up to 9 mg K l-1 in the culture solution; above this level yeild declined. In contrast, populations from calcareous soils, not fertilized with K, responded to K up to the highest level used, 81 mg K l-1. Populations from unlimed plots of the Park Grass Experiment, fertilized with K, responded more than all other populations up to 81 mg K 1-1. One population, collected from a limed soil also fertilized with K, responded least to K. If this latter population was disregarded, there was a close correlation (r=0.92) between response to K, over the range 1-81 mg K 1-1, and the extractable K content of the native soil of each population. Differences between populations in shoot concentrations of K were not correlated with yield response to K, but populations from limed soils generally achieved maximum yield at lower shoot K concentrations than did those from unlimed soils. The yield of all populations was little affected by the Mg concentration applied and populations did not differ in response to Mg. The abundance of A. odoratum is not affected by Mg supply on the Park Grass Experiment and it is concluded that no population differentiation has occurred in response to this nutrient.