ETUDE DU POUVOIR NUTRITIF EN PHOSPHORE DE CERTAINS SOLS DU QUEBEC A L'AIDE DU 32P

Abstract
In a pot-type experiment with ryegrass, 32P was used to label isotopically exchangeable soil phosphorus as well as a phosphate fertilizer. The tagging of both forms of phosphorus enable us to determine the pool (L) for soil reserves and the A value which is the availability of these reserves in the presence of fertilizer. The authors establish correlations between the ratio K = L/A and the assimilable phosphorus as determined by the Bray II method, and also between K and the "extra" phosphorus. The authors state that the latter was the difference between the plant phosphorus with and without fertilizer. From this study it is concluded: (1) that the K value seems to be a better criterion than the amount of assimilable phosphorus to estimate the phosphorus fertility of a soil; (2) that the study of the variation of the K value according to the soil types informs us about the reserves behavior and about the way of nutrition for the plant. The calculation of the K value is aimed toward a more adequate fertilization for given types of soil.

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