Avaliação das taxas de mineralização do carbono e nitrogênio do composto orgânico proveniente de carcaça e despojo de pequenos ruminantes

Abstract

The determination of the mineralization rate of organic compost is necessary for planning the most efficient way to use them. Thus, this study aimed to determine the carbon and nitrogen mineralization rate from organic compost produced from sheep and goat carcasses and its slaughtering spoils. Chromic Inceptisol (Luvisols) samples were incubated at an average temperature of 30.5 ° C with doses of 0; 3.75; 7.5; 15 and 30 Mg ha-1 of organic compost. To evaluate the carbon mineralization were used 100 g of soil incubated with these doses arranged in a completely randomized design (CRD) distributed in a split plot scheme. Samples were kept in glass containers tightly closed and the C-CO2 measurements were performed during periods of 0; 1; 2; 3; 4; 5; 6; 7; 9; 11; 14; 17; 20; 23; 26; 29; 33; 37; 41; 48; 55; 69; 83; 97; 112 and 126 days after the start of incubation. To determine the nitrogen mineralization rate (N), the doses of compost were incubated with 100 g of soil and distributed in a CRD with a 5 x 10 factorial arrangement. The assessment of inorganic N were performed at 7; 14; 28; 42; 56; 70; 84; 98; 112 and 126 days after the incubation beginning. Both models, the simple exponential and the double exponential, were not efficient to explain the dynamics of C mineralization for not consider the interactions that occurs when the compost is applied to the soil. A model that considers the soil C labile and recalcitrant compartments (ls and rs), protected and unprotected compartments of the applied organic matter (OM) (pc and dc) and a p factor that modifies the rate of mineralization of soil organic matter (SOM) when the compost is applied (C0 = Cls e-kltp + Crs.e-krstp + Cpc .e-kpst + Coc .e-kdct) was more efficient to explain the dynamics of C, considering the interactions with the SOM and the OM added. The suggested model has demonstrated that the rate of SOM decomposition is approximately 10% greater in the presence of the compost and the compost mineralization rate is 0.012 day-1, explaining the 97.95% of the variability in the data. The N mineralization was very fast since 40% of the standard dose of 7.5 Mg h-1 was found in the mineral form 14 days after the incubation. However, due to losses of inorganic nitrogen by NH3 volatilization, it was not possible to estimate the actual N mineralization rate.