Abstract

Decomposition kinetic of applied compost in soil depends on the decomposition rate coefficient (k), environmental conditions and the interactions with soil. However, studies with the aim of determining k values for different materials rarely consider interactions with soil. The objective of the current study was to estimate k value of an organic compost, considering the interactions with the soil. Samples of soil mixed with compost were incubated in hermetic recipients for 126 days and evolved C-CO₂ was quantified. Nonlinear models proposed in the present study were fitted to evolved C-CO₂ data. Better fitting was found in a model that divided the soil organic matter in four pools (labile and recalcitrant native soil organic matter; protected and unprotected added organic matter), values of k on both native organic matter pools were multiplied by a constant denominated priming (pr) only in the cases where the compost was added to the soil and the amount of C in the protected pool is limited to the soil protection capacity. Organic compost produced using carcasses, sheepfold residues and slaughterhouse residues presented k value equal to 0.01179 day^-1 at 31 ^oC without water stress. Compost application increased in 9.8% the decomposition of the native soil organic matter.

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