No-linear respiration dynamics in a degraded Alfisol amended with different dose of salmon sludges

Abstract

No research has been conducted regarding respiration model parameters as a consequence of the application of salmon sludge on degraded Alfisols. In order to investigate kinetic parameters representing the decomposition of salmon sludge by means of respiration rates, sediment samples from a land-farmed pisciculture and a lake-salmon facility were applied to a degraded Alfisol at the Biobío region (Chile). Soil microbiological activity was evaluated on a 60-days laboratory incubation experiment under different salmon sludge addition dose: T1: 25 t ha-1; T2: 50 t ha-1; T3: 75 t ha-1; T4: 100 t ha-1; T5: 150 t ha-1. A non-amended soil served as control. CO2-C production was determined in samples under closed incubation. A two-component firstorder regression model was applied to CO2-C curves to obtain kinetic parameter values of C mineralization. The analysis confirmed that microorganisms increased their respiratory activity with time and increased sludge concentration (p ≤ 0.05). A higher microbial activity was noted when soil was amended with land-farmed sludge at 100 and 150 t ha-1, particularly after 30 days of incubation. The model showed that microorganisms needed more time to decompose labile C compounds in the salmon sludge when dose increased above 100 t ha-1. After 60 days of incubation, land-farmed sludge amended at 25 t ha-1 accumulated 44% of CO2-C from a labile C source and 56% from a mineralized C pool, whereas at 150 t ha-1 showed a 76% of a labile C and 24% mineralized C.