CARBON MINERALIZATION KINETICS AS INFLUENCED BY SOIL PROPERTIES

In a short-term laboratory study C mineralization potentials were dete rmined on soil samples obtained from some representative agricultural soils in Tuscany, Italy. All the kinetic models tested to describe the mineralization process provided a good fit to the experimental data. A modified first-order model best described C mineralization in the so il. Both potentially mineralizable C and the mineralization rate (k) v aried considerably among soils, reflecting the differences in soil pro perties. Potentially mineralizable C was positively related to C evolv ed as CO2 and to the exchange capacity. Normalized values (potentially mineralizable C divided by organic C), representing on average about 2% of the total soil C, was positively correlated to soil pH and negat ively to the soil C pool, the soil N pool, and total microbial activit y. Values for k ranged between 0.050 and 0.104 day(-1), being higher i n fine-textured soils and in soils with a large free Fe content. A low C:N ratio was indicative of a high k value. Turnover times for minera lized C were relatively rapid, ranging from 10 to 20 days.