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 aimed to describe and to compare the fit of the nonlinear sigmoid models, Logistic and Gompertz, to the CO2 mineralization of four legume species over time in the soil, and indicate the most suitable model. Furthermore, it is also proposed to evaluate the CO2 mineralization of legumes from two different edaphoclimatic conditions when added to the soil under controlled temperature and 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). A randomized block design with four replications was used. The soils from both areas are classified as Red-Yellow Latosol and have a clayey texture. The mineralized carbon was measured at 48, 96, 144, 192, 240, 312, 384, and 480 hours from the beginning of incubation. Legumes in different locations had the same amount of potentially mineralizable carbon, and microorganisms had the same adaptation time to reach the maximum decomposition rate. The maximum decomposition rate occurs at the beginning of mineralization, and therefore the Gompertz model was more suitable than the Logistic model in describing the decomposition of the four legumes in the soil.

Keywords

• Decomposition
• Mineralization
• Gompertz Model
• Logistic Model