ABSTRACT

FIGURE 10 The relationship of total solution phosphorus (Ps) to pH and total soil oxalate content in a typic Argixeroll of Wyoming. The multiple linear regression model is -log Ps = -2.70 + 0.70 log (soil oxalates) + 0.15 pH; r 2 = 0.925. (Unpublished data of Knight.)

hydroxyapatite equilibrium and best represents the field case. The effect of pH as a consequence of increasing PC02 is much less dramatic in the whewellite-hydroxyapatite system because of the comparatively small pH sensitivity of CaC204 as opposed to that of CaC03' Althougll unable to delineate the. stable mineral phase controlling solution P in the soil, unpublished data from the systems studied by Knight et al. (1989) yielded a strong relationship between soil oxalates, pH, and total solution P (Fig. 10).