Management impacts on soil carbon sequestration: A case study evaluating perennial and annual cereal production systems

Background/Question/Methods

Agriculture has a tremendous ‘ecological footprint’ as it is a leading contributor to carbon dioxide emissions, and other potent greenhouse gases. At the same time, innovative agricultural practices have the potential to mitigate climate change, by sequestering carbon. A transformative approach to a more sustainable agriculture has been proposed through developing perennial grain cropping systems, which produce edible grain without the need to till and replant every year. This new type of grain crop has the potential to enhance ecosystem services such as soil conservation, and soil C sequestration. In June 2012, deep soil cores (1m) were taken at the Kellogg Biological Station (KBS) in a field experiment with contrasting cereal crops, an annual winter wheat and a perennial intermediate wheatgrass. The crops are grown under a management gradient (Organic, Low N conventional, and High N conventional), providing an opportunity to test interactions of species with management.  We quantified above and belowground biomass as well as soil C (labile fraction) in each system to determine whether or not soil C increased under the perennial grain system.

Results/Conclusions

The perennial intermediate wheatgrass systems had higher total biomass across all three managements (Organic, Low N conventional, and High N conventional) compared to annual wheat. Total root biomass (fine and coarse roots) was three to four times greater in the perennial systems (P < 0.05) compared too annual rot biomass. In both annual and perennial systems, root biomass was highest in the High N management system, however, significant differences across management were not evident. The annual wheat systems tended to have higher aboveground total root biomass compared to perennial intermediate wheatgrass however, these results were not significant. Root to shoot ratios  were significantly higher (P < 0.05) in the perennial systems compared to the annual wheat systems, indicating that perennial roots invest more to belowground biomass than their annual counterparts.  Labile soil C fraction (POXC) was significantly higher in perennial intermediate wheatgrass compared to annual wheat under conventional management (P <0.05). However, under organic management, POXC values were higher in annual systems compared to perennial systems. This shows the complexity of management interactions with plant species type, and the potential of novel perennial cereals to sequester C over time.