Investigating the Link Between Drought, Cattle Management and Soil Carbon
This project studied the role of different cattle grazing systems in maximizing carbon storage and minimizing greenhouse gas (GHG) emissions throughout Alberta’s grasslands. Funded through the Biological GHG Management Program in 2015, the project aimed to better understand how grazing affects carbon storage in grasslands and the role grazing plays in mitigating drought impacts and reducing GHG emissions.
Grasslands can store twice as much soil carbon as adjacent cropland, which means they are important in the battle to reduce GHG emissions – but the relationship between grazing and carbon storage is unclear. Given this, cattle management that manipulates grassland ecosystems to increase soil carbon is beneficial for reducing GHGs. However, new management approaches must also increase the production stability of forage, the plant material eaten by grazing livestock, to ensure cattle operations are profitable. It is also necessary to understand how drought-related changes in plant quantity and quality will affect cattle and the overall carbon balance of the ecosystem. Using the variation in GHG flux and indicators of carbon change in response to grazing treatments and rainfall conditions, the researchers aimed to gain insight and suggest potential grazing scenarios that could be adopted by cow and calf producers in Alberta’s grasslands. GHG flux was measured using a gas chromatograph, which is an analytical instrument that measures the content of various components in a gas sample. Samples were collected by static chambers driven into the soil. The resulting indicators are important to informing offset programs for the conservation and sequestration of soil carbon.
The Complexity of Grassland Ecosystems Remains a Challenge
Completed in 2021, the results from this study how a complex picture of grassland ecosystems response to different simulated grazing and drought conditions. The researchers identified that more arid grasslands in Alberta are more sensitive to the combined effects of drought and grazing. Overall, the results suggest that responses are very site-specific, likely the result of local weather, climate, soil or vegetation properties at a particular site. Consequently, it is challenging to make consistent recommendations for grazing management that will lead to enhanced resistance of forage to drought or mitigation strategies for GHG reductions. Importantly, the researchers found that increased levels of organic debris such as plant matter, or agricultural litter, on the soil’s surface mitigated plant sensitivity to drought to some degree. This suggests grazing management that reduces the impacts on plant production and allows the development of an agricultural litter layer may be an important strategy in the future to combat drought sensitivity.
What’s next?
While this project determined some indicators of carbon sequestration, the researchers suggest future work should focus on working with cow-calf producers to enact and test grazing management scenarios identified here that may both increase carbon storage and provide more resilient forages under drought. Furthermore, since the implementation of this project, carbon offset protocols have made some progress. Future work should engage with organizations involved in these endeavors to ensure that not only are beneficial management practices recognized but that measurements taken in research projects align with verification protocols.