Vertical Distribution of Soil Phosphorus and Potassium on Several Established Alfalfa Stands That Received Various Rates of Annual Fertilization
1961
Wells, K. L. | Parks, W. L.
Available soil phosphorus, available soil potassium, calcium, magnesium, and pH were determined at various depths on four soil profiles under established stands of alfalfa. Three experiments were set up in a complete factorial design using four rates of annual phosphate application and five rates of annual potash application. The fourth experiment received five annual applications of potassium and no applications of phosphate since it was on soil inherently high in phosphate. Available potassium after 4 years of annual applications of potash on three soils and 5 years on one soil was concentrated in the 0- to 6-inch layer. Only a slight movement of potassium into depths below 6 inches was noted even at high rates of annual potash fertilization. Available soil phosphorus was found to be concentrated in the 0- to 3-inch layer. It was found that annual potash and phosphate applications had little effect on soil reaction. Significant difference in yield at the 0.05 level of probability was found between the 0- and the 100-pound-peracre annual potash treatment in each experiment, and between the 0- and the 60-pound-per-acre annual phosphate treatment on those experiments receiving phosphate fertilization. No significant response to higher rates of annual todressing was obtained. Yield data were correlated with soil test potassium values of various soil layers. A poor correlation was found to exist between soil test potassium values and yield. Correlation values were increased by addition of phosphorus soil test values into the equation.
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