01848naa a2200193 a 450000100080000000500110000800800410001910000130006024500980007326000090017152013260018065000130150665000130151965000090153270000190154170000170156070000160157777300610159318273122011-10-17       1955    bl ---       0--  u    #d1 aAMER, F.  aCharacterization of soil phosphorus by anion exchange resin adsorption and P32-equilibration.  c1955  aAdsorption of phosphate by the anion-exchange resin Dowex-2 was investigated. The resin adsorbed small quantities of P from solution quantitatively. The rate of P-adsorption by resin agitated in solution was proportional to the P-concentration in solution, and was independent of the rate of diffusion of adsorbed P in the resin. When 1 g of soil was shaken continuously with 1 g of resin in 100 ml of water, the rate of P-adsorption by the resin was controlled by the rate of P-release from the soil. Quantities of P adsorbed from soil by resin after different lengths of time were less than those equilibrated with P32 during the same time intervals. The curves showing quantity of P adsorbed vs. time could be satisfactorily described by the hypothesis that there were three simultaneous reactions differing in rate, each reaction being first-order with respect to P. The same was true of the P32-equilibration data, except that the rate of the slowest reaction was apparently independent of time. In a group of 16 soils, the correlation between P adsorbed by the resin in 2 hours and P-availability to plants in the greenhouse, measured by the isotope-dilution method of Fried and Dean, was 0.95. The corresponding correlation between P extracted by the 0.25N HCl — 0.03N NH4F extractant of Bray and Kurtz was 0.91.  aAnálise  aFósforo  aSolo1 aBOULDIN, D. R.1 aBLACK, C. A.1 aDUKE, F. R.  tPlant and Soil, The Haguegv. 6, n. 4, p. 391-408, 1955.