Fitting of decomposition of sewage sludge and oat straw by nonlinear models

Abstract

An economic and environmentally feasible way to recycle sewage sludge is its use in agriculture. Information on carbon mineralization curves allows us to seek improvements in soil quality and crop productivity. The objective of this work was to evaluate the nonlinear models that describe carbon mineralization in the soil. The experiment was conducted in laboratory and the design was completely randomized, with four replicates and three treatments. The following treatments were evaluated: sewage sludge, black oat straw and sewage sludge + oat straw, incorporated into the soil. Pots with soil and the applied treatment were incubated for 110 days. The Stanford and Smith and Cabrera models were used, considering structure of autoregressive errors AR (1) when necessary. The fittings were compared using the Akaike Information Criterion (AIC). The evaluated nonlinear models described the carbon decomposition dynamics of the treatments satisfactorily. The Stanford and Smith model is suitable for describing the carbon decomposition in the soil + sludge and soil + oat straw treatments. The Cabrera model is suitable to describe the carbon decomposition of the soil + sludge + straw treatment.