Interaction between iron(III)-diphosphate and iron(III)-triphosphate and Ca-form of a clayey meadow soil was followed over a period of three days using radiotracer technique and kinetic evaluation of the results performed.59Fe served to determine the quantity of iron,45Ca to measure the calcium, and phosphorus was measured spectrophotometrically. Approximately 80% of both iron chelates disappeared from the solution during the time of the experiment as a result of two well distinguishable reactions. One of them is a rapid interfacial process of about 10 minutes and the other is a slow reaction leading to the decomposition of iron(III)-polyphosphate chelates. The two processes could be separated using the Christiansen equation.
Interaction between FeEDTA and calcareous soils was followed over a period of four weeks using a radiotracer technique, and a kinetic evaluation of the results was performed.59Fe served to determine the quantity of iron,14C to assay for EDTA and45Ca to measure calcium. During the experiment, i. e. within four weeks in case of the chernozem soil 61% and in case of the clayey meadow soil 51% of the iron chelate dissapeared from the solution. The loss in soluble iron was partly due to a rapid sorption process of about an hour and partly due to the slow decomposition of FeEDTA to Fe(OH)3. The two processes could be separated using the Christiansen equation.