Crop rotation and tillage impact on carbon sequestration in Saskatchewan soils
Six field experiments from the Brown to Black soil zones and from light- to heavy-textured soils in Saskatchewan were conducted to quantify C sequestration under different tillage and crop rotations. Continuous cropping compared with crop rotations containing various frequency of fallow sequestered soil C ranging from 0.5 to 6.7 Mg C ha-1, depending on the duration of experiments, frequency of fallow and soil texture. This increase in soil organic C under continuous cropping varied from 36 to 453 kg C ha-1yr-1. The potential for sequestering soil C with continuous cropping was greater in the Dark Brown and Black soil zones than in the Brown soil zone even through the frequency of fallow was greater in the Brown soil zone. No-tillage compared with conventional tillage also sequestered soil C ranging from 0.6 to 13.2 Mg C ha-1. This increase in soil organic C under notill varied from 50 to 528 kg C ha-1yr-1. With elimination of both tillage and fallow, the soil organic C increase was approximately 200 kg C ha-1yr-1 in the Brown soil zone regardless of soil texture, and from 600 to 800 kg C ha-1yr-1 in the Dark Brown and Black soil zones. Relative annual increase in soil organic C under no-till was approximately a linear function of clay content. This study also indicated that potential gains of soil organic C under no-till were not necessarily related to the level of soil organic C prior to adoption of no-till. Heavy-textured soils would have a greater potential for gains in soil organic C under no-till in the prairie soils.
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