Growing legumes to reduce greenhouse gases

Grazing animals like cattle, sheep and horses need forage from pastures — and pastures need to be reseeded and fertilized from time to time. Traditional fertilizers like nitrogen and carbon can rejuvenate grass pastures and boost their nutritional value, but they also drive up the production of greenhouse gases (GHGs) like nitrous oxide, methane and carbon dioxide.

J. Diane Knight, a professor of soil science at the University of Saskatchewan’s College of Agriculture and Bioresources, may have found a solution. Knight is studying how seeding grass pastures with nitrogen-fixing legumes can rejuvenate them and help them last longer while also reducing the GHGs they emit.

The impact of forage composition on greenhouse gases

In pastures, GHGs can originate from urine and dung patches, cattle belches, mechanical management and soil carbon changes — and some of these causes can be addressed by changing the forage. Prof. Knight’s study investigated how two non-bloat legumes, cicer milkvetch and sainfoin, affected the nitrogen and carbon balance in a grazed pasture system compared to more traditionally managed meadow bromegrass.

She and her team found that per unit of cattle weight gain (or per amount of meat produced), pastures rejuvenated with these two legumes emitted 17% fewer emissions than pastures composed mainly of bromegrass. The researchers also found that the cicer milkvetch and sainfoin were easier for the cattle to digest.

Choosing the most persistent legume

Between sainfoin and cicer milkvetch, the latter was ultimately deemed best for the job, mainly because it persisted longer in the pasture.

This study sheds light on how providing Canadian producers with the latest research can help them make informed agricultural decisions — and how these decisions can benefit farmers, animals and our environment alike.

Want to learn about more research projects carried out under this program? Follow our Good News Grows and The First Sixteen Podcasts initiatives for other examples of how the AGGP helped give producers a better understanding of greenhouse gas emissions and nutrient losses from agricultural systems.