The effect of K fertilization and K removal by ryegrass in pot experiments on the K concentration of the soil solution of various soils

Summary

The effect of K fertilization and K removal by perennial ryegrass grown in potson the K concentration of the soil solution of very different soils is described. The following results have been obtained: 1) With similar content of exchangeable K the K concentration of the soil solution varies widely according to soil properties. 2) Equal amounts of fertilizer K increase the K concentration of the soil solution to a different extent depending on soil properties. 3) The level of the K concentration of the soil solution alone does not indicate how rapidly it can be raised by K supply. A diagram based on the evaluation of both parameters (i.e. exchangeable K and K concentration of the soil solution), however, will give a good picture of the K dynamics of a soil. 4) The K desorption curves obtained by EUF and the K concentration of the soil solution show similar changes after K fertilization. 5) The highest yields were obtained with the highest K concentration in the soil solution. 6) The depressions in yield observed in the course of the four cuts differed among the various soils and were in line with the decrease in the K concentration of the soil solution. 7) With similar contents of exchangeable K, equal removals of K affected the K concentration of the soil solution to a different extent. The exchangeable K alone, therefore, cannot be considered as a reliable parameter of the buffer capacity of the K concentration in the soil solution. 8) The course of the K desorption curves gives good information on the rate of decrease in the K concentration of the soil solution due to plant removal. Thus the yield curves are in good agreement with the course of the corresponding EUF curves.