Abstract
To study Assessing the impact of tillage practices on soil carbon losses dependents it is necessary to describe the temporal variability of soil CO2 emission after tillage. It has been argued that large amounts of CO2 emitted after tillage may serve as an indicator for longer-term changes in soil carbon stocks. Here we present a two-step function model based on soil temperature and soil moisture including an exponential decay in time component that is efficient in fitting intermediate-term emission after disk plow followed by a leveling harrow (conventional), and chisel plow coupled with a roller for clod breaking (reduced) tillage. Emission after reduced tillage was described using a non-linear estimator with determination coefficient (R²) as high as 0.98. Results indicate that when emission after tillage is addressed it is important to consider an exponential decay in time in order to predict the impact of tillage in short-term emissions.
Highlights
There has been a great deal of interest in studying soil CO2 emission of agricultural areas, especially when the use and management of soils are considered
The main hypothesis is that soil CO2 emission after tillage is modulated by two components: the first directly related to soil temperature and soil moisture, and the second related to an expected rapid dynamics of the additional labile carbon induced by tillage
The exponential decay in time after tillage coupled with a model for linear dependence on soil temperature and soil moisture is a more adequate model to describe, in this case, emission after conventional and reduced tillage
Summary
There has been a great deal of interest in studying soil CO2 emission of agricultural areas, especially when the use and management of soils are considered. Due to the high spatial and temporal variability of soil CO2 emission the uncertainty on this topic is significant; it is already accepted that reductions in tillage intensity and frequency could help achieving soil carbon recovery (BRONICK & LAL, 2005). Changes in soil carbon decay rate are expected with decreases in soil bulk density and increases in soil pore volume. Based on these assumptions, conceptual models have been proposed to describe the tillage induced emission. REICOSKY & ARCHER (2007) suggested that the process is described by an initially rapid decline in CO2 flux followed by a slower flux, requiring the use of a two-step function.A new two-step model is presented in order to fit emissions after tillage.
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