Uptake of phosphorus and other nutrients by oats from soils with various clay contents

The pot experiment was carried out to study the effect of the clay content on the uptake of phosphorus and some other nutrient elements by oats. Two different series of soil mixtures were prepared with increasing additions of clay soil up to 25 vol. % clay, the additions being made both to fines and and Sphagnum peat soils. The content of phosphorus in plants and the yield increased to some extent in fines and/clay soil mixtures with an increase in the clay content. In peat soil increasing additions of clay soil caused a decrease in the phosphorus content of the plant but had no significant effect on the amount of the yield. In fines and/clay soils the uptake of phosphorus by the oat from the fertilizer increased from3 to 10 %, in peat/clay soils it decreased from 60 to 20 % with an increasing clay content of the soils. The isotope dilution method was not applicable in the determining of the labile phosphorus of the experimental soil mixtures. This was assumed to be due to the small concentrations and concentration differences in soluble native soil phosphorus and to the strong fixing capacities of the soils. The contents of other nutrient elements in plants generally decreased with an increasing clay content. The most marked exceptions in this respect were the content of phosphorus in plants growing on fines and/clay soils and the content of potassium and manganese on peat/clay soils