A simple model for quantifying change in soil organic C as influenced by tillage and crop rotations on the Canadian prairies
Simulation models are required for quantifying the impact of crop rotations and tillage on soil organic C dynamics, and for aggregating C sequestration over a relatively large area. However, most current models of soil organic C have been built based on kinetically defined discrete pools with different turnover times. Those pools of soil organic C only exist conceptually. They have not been determined experimentally, thus validation of kinetic models describing soil organic C turnover is usually difficult or not independent from actual measurements. Thus, there is a need to develop a simulation model that can be easily validated and used for estimating future projection of C sequestration under specified management practices. A simple model has been developed to quantify the impact of crop rotations and tillage on soil organic C and validated using long-term field experiments conducted on the Canadian prairies. This simple model required a few input parameters and accurately predicted the change of soil organic C with a relative error of 5% or better. Crop rotation in cereal-dominant cropping systems, affected the amount of soil organic C due to differences in the amount of crop residue inputs. Clay content of soil played a vital role in determining the soil organic C sequestered under conservation tillage compared to tilled systems. This study also showed that the rate constant of soil organic C turnover was about the same for all systems in the drier region of the Canadian prairies, regardless of soil texture and the cropping system.
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