SEASONAL DYNAMICS OF THE READILY SOLUBLE- P AND SOLUBLE-K CONTENTS OFSOIL ON CALCAREOUS SANDY SOIL

In a fertilization trial set up on calcareous, slightly humic sand in rye stand in the year following the build-up by phosphorus and potassi um, soil-samples were taken during the vegetation period (March-July) generally at 10 days. In these samples the changes in the ammoniumlact ate-content and water soluble phosphorus and potassium in the ploughed layer were measured and in that located just below it. Based on the r esults the following main conclusions may be drawn: The AL-soluble P2O 5 content in the poloughed layer and in the one directly below it, wit hin the same treatment, showed also statistically proved dynamics only in the control and phosphorus-deficient treatments; The AL-soluble K2 O-content of the soil indicated in both soil-layers during the vegetat ion period in the majority of the treatments significant seasonal dyna mics; characterized by the fact that the content was in the spring sam ples in all treatments higher, while at the other dates nearly the sam e; The water-soluble P-content of the soil showed proved seasonal dyna mics only in the ploughed layer, within the N and PK treatments; The w ater soluble K-content indicated in both soil-layers in the majority o f the treatments statistically proved periodical changes. The change r eached maximums in spring; The effect of fertilization (PK) could be w ell followed both in AL-and water-soluble groups within each period an d on the average of those in both layers; Between AL- and water-solubl e P a correlation (r = 0,77) and between K (r = 0,82) was found. On li ght sandy soil in the first year after PK replenishment due to the dif ferences of various sampling dates in AL and especially in water solub le P and K parts, they can be utilized in expert advice to asses suppl y only on the basis of great number of sampling carride out periodical ly at the same time.