Greening up farming.

Maren Oelbermann and a grad student doing research.

School of Environment, Resources and Sustainability (SERS) professor Maren Oelbermann, right, shows graduate student Nicole Spiegelaar how to prepare soil samples for analysis. Oelbermann is an expert in soil.

Farms seem like green places. And it’s true, plants and soil store carbon, helping keep the planet cool.

But overall, nitrogen-based fertilizers, gas-guzzling tractors, and belching cows all make agriculture “a little bit of a bad boy” when it comes to greenhouse gas emissions, says environment and resource studies professor Maren Oelbermann.

Oelbermann is researching ways to make farms capture and store more greenhouse gases than they emit.

Intercropping — planting two or more different crops in the same field, at the same time — can help farms store more carbon, she says.

She and two colleagues have estimated that if 40 per cent of Canada’s marginal agricultural land were intercropped, enough carbon would be captured over eight years to represent 32 per cent of Canada’s commitment to reducing emissions under the Kyoto protocol.

One form of intercropping, agro-forestry, integrates trees with traditional crops or livestock. The trees can be a source of revenue by harvesting them occasionally or using them to grow crops such as fruit or nuts.

Trees also store carbon, prevent soil erosion, and help maintain water quality in streams. The leaves they shed help improve soil fertility.

Planting traditional crops together also has benefits. In a project of Oelbermann’s in Argentina, corn and soybeans are grown in alternating alleys. The soybeans fix nitrogen in the soil, and after the corn is harvested, plant residue is left on the ground. Both improve soil fertility.

More fertile soil stores more carbon and requires less fertilizer. Less fertilizer means lower nitrous oxide emissions, which is important because as a greenhouse gas, nitrous oxide has around 300 times the warming power of carbon dioxide.

In the long run, changing farming practices could cut fertilizer costs as well as providing services such as carbon capture, improvement of water quality, and conservation of biodiversity, says Oelbermann.

“These kinds of services not only benefit the farmer, but society as a whole.”