Phosphate fertilizers are widely applied in modern agriculture. The phosphate supplies,
however, are rather limited, so the economical application of phosphate fertilizers
Phosphate anions react with the different soil components, different interfacial and
reaction occur, a part of them sorb phosphate very tightly. The ratio of the sorbed
species can be studied by heterogeneous isotope exchange, the portion of utilized
can be determined in this way. Unfortunately, the models applied in the literature
treatment of heterogeneous isotope exchange base on incorrect principles.
The ratio of these species on some Hungarian soil types was studied by radioactive
method using 32P isotope as phosphate ion. The effect of soil type, phosphate quantity,
incubation time and plant growing was studied. The ratio of weakly sorbed phosphate
studied by heterogeneous isotope exchange; the quantity of water soluble/weakly sorbed
phosphate as well as the transport rate of phosphate in a steady state between the
soil and soil
solution was determined. The evaluation was made by a correct thermodynamic and mathematical
model for the evaluation of the heterogeneous isotope exchange.