The Q/I ratios of contrasting soils of the Saragossa Province (Spain) were studied. Samples of the soils were treated with varying quantities of a monocalcium phosphate solution to yield ranges of 0 to 400 ppm applied P. The samples were incubated at saturation for one week, after which they were placed in Buchner funnles. P was determined in water extracts obtained by suction. These quantities of P were plotted against the amounts of applied phosphorus and the resulting P-sorption curves were found to differ widely among soils. The results obtained were significantly affected by the nature and the concentration of slats present in the soils. Soils with much sodium chloride and calcium sulphate and higher P-sorption capacities than had those with calcium chloride. Those containing calcium and sodium sulphates showed positive correlations between salt concentration and phosphate sorption. Maximum P adsortion values were strongly influenced by degree and nature of salinity. A sequence was obtained according to the composition of the salt presen. That is: sodium calcium sulphates> sodium chloride + calcium sulphate> calcium chloride + sodium sulphate> sodium chloride and sodium sulphate. The range of the values was: (667 to 200 ppm P)(425 to 320 ppm P) (348 to 223 ppm P) ande 233 to 127 ppm P) resperctively.

Peer reviewed