Sigmoid models in the description of CO₂ evolved from legumes in the soil

Abstract

The decomposition of legumes in the soil over time can be described by nonlinear sigmoid models. Thus, this study aimedto describe and to compare the fit of the nonlinear sigmoid models, Logistic and Gompertz, to the CO2 mineralization of fourlegume species over time in the soil, and indicate the most suitable model. Furthermore, it is also proposed to evaluate the CO2mineralization of legumes from two different edaphoclimatic conditions when added to the soil under controlled temperatureand humidity conditions. The following legume species used in green manure were evaluated: Arachis pintoi (forage peanut),Calopogonium mucunoides (calopo), Stylosanthes guianensis (Caribbean stylo), and Stizolobium aterrimum (mucuna). Arandomized block design with four replications was used. The soils from both areas are classified as Red-Yellow Latosol andhave a clayey texture. The mineralized carbon was measured at 48, 96, 144, 192, 240, 312, 384, and 480 hours fromthe beginning of incubation. Legumes in different locations had the same amount of potentially mineralizable carbon, andmicroorganisms had the same adaptation time to reach the maximum decomposition rate. The maximum decompositionrate occurs at the beginning of mineralization, and therefore the Gompertz model was more suitable than the Logistic modelin describing the decomposition of the four legumes in the soil.