Nonlinear modeling of carbon dynamics in soil treated with tannery sludge

Abstract

In 2020, the Brazilian commercial cattle herd was the largest in the world, representing 14.3% of the worldwide herd, with201.7 million heads. Although this activity yields significant profits, contributing to the economic and social development ofBrazil, it has been the target of concerns, mainly due to the large production of waste/effluents associated to bovine leatherprocessing. In this scenario, mineralization is important because nutrients essential for plant growth are released duringthe process of organic waste decomposition, and the dynamics of carbon release can be described by nonlinear regressionmodels. Thus, this study aimed to model the mineralization of organic carbon in the soil for 6, 12, 24, and 36 megagramsdoses per hectare (Mg ha−1) of tannery sludge using the Stanford & Smith, Cabrera, and Juma nonlinear models. Very clayeysoil samples were used: eutroferric red nitosol (NVef). Mineralized carbon was measured in 21 observations over time untilthe 105th day of incubation. Parameters were estimated using the least squares method. Adjustments were compared usingthe corrected Akaike information criterion (AICc) and the adjusted coefficient of determination (R2aj) as selection criteria. The Cabrera model had the best adjustments for doses 6, 12, and 24 Mg ha−1 and Juma for dose 36 Mg ha−1, based on the selection criteria used. Although the Stanford & Smith model is the most widely used in the literature to model soil carbon dynamics, its use was not the most appropriate for any of the doses evaluated in this study. The higher the dose of tannerysludge, the greater the amount of potentially mineralizable carbon.