ChileanJAR

A model to forecast kinetic isotopic exchange was applied to ten soils fromthe tenth region of Chile with the aim to characterize the kinetic parameters and calibrate a multicompartmental model of bioavailable P. The soils were shaked up to equilibrium and then a labeled solution of ³²P was added. The analysis were made at two sampling times. The green malachite method was used to measure the concentration of P in the soil solution and the liquid scintillation method with a Beckman counter LS 5000 was used to measure the initial and the final radioactivity. The quantity, intensity and capacity factors were measured and also the kinetic parameters Fm, Km and Tm. Values less than 0.02 mgPL^-1 for the intensity factor, and between 0.07 and 2.4 mgPk^-1 for quantity factor were considered to be limiting for crops. The immediately available pool of P was slightly higher in the Crucero soil under fallow than in the other two management systems. The A, B and C pools showed a relatively homogenous distribution. In the Crucero soil under pines the unique source of P for plants comes from the pool D, which will decrease gradually as it is absorbed by plants. In the Crucero soil with wheat the major part ofP is found in the pool A coming from the recent application offertilizers.