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.
Highlights
Organic composts are used since ancient times in agriculture to fertilize and improve physical, chemical and biological soil properties (Blum, 1992)
The k value should not vary due to the applied dosage. The occurrence of this variability indicates the existence of interaction between applied organic material and soil matrix or with native soil organic matter, evidencing the necessity of including these variables in the carbon decomposition model
Organic compost produced using carcasses, sheepfold residues and slaughterhouse residues presented a k value equal to 0.01179 day-1 at 31 oC without water stress. Application of this compost increased in 9.8% the decomposition rate of native soil organic matter
Summary
Organic composts are used since ancient times in agriculture to fertilize and improve physical, chemical and biological soil properties (Blum, 1992). Composting consist in the transformation of fresh organic residues into more stable organic material, which is advantageous compared to the application of fresh organic materials (Zhang et al, 2012) Among these advantages, could be featured: (i) Volume reduction, facilitating the storage and transport; (ii) stabilization and homogenization allowing storage, management and scheduling of its use as fertilizer (Orrico, Lucas Júnior, & Orrico Júnior, 2007); (iii) Pests and pathogens elimination due to the high temperatures (over 60 oC) reached during the composting process (Noble & Roberts, 2004). The knowledge of the decomposition kinetics of compost in soil allows the establishment of a correct dosage and scheduling application. This planning aims the maintenance of soil organic carbon and the correct supply of nutrients, avoiding contamination and soil degradation.
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