Scitech | The dirt on dirt

A look at soil ecology research at McGill

Soil ecology is a relatively young field, having emerged in North America in the mid-1990s. The rising demands for enough food to sustain the swelling global population has given increasing importance to research in this field. Joann Whalen, a professor in the Department of Natural Resource Sciences, and her lab at McGill’s Macdonald campus, is concerned with soil ecology and, in particular, the study of nutrients in fertilizers.

Many current fertilizers release compounds such as carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) – otherwise known as greenhouse gases – into the environment. In large amounts, these greenhouse gases are harmful to the climate and cause ozone depletion. Large amounts of nutrients like nitrogen and phosphorus find their way into runoff from agricultural land masses and have been associated with eutrophication, the process where excess nutrients in water bodies stimulate excessive plant growth. Eutrophication has many ecological consequences, including toxic effects on the environment and decreased biodiversity.

Efficiency is of special concern when looking at nitrogen fertilizers. Soil systems tend to be leaky in their retention of nitrogen. Therefore, tools that enable the prediction of nitrogen release by the soil nutrient cycle would be useful in determining when, and how much, nitrogen fertilizer is needed for crops with high nitrogen demands, lowering costs as well as environmental risk.

By addressing these questions, the Whalen lab is seeking to reduce the amount of nutrients released into waterways and the atmosphere, while increasing their efficiency by finding a comprehensive solution to the drawbacks of current fertilizers.

In addition to investigating nutrient cycling in soil cycles, the lab also studies soil microbiology. While examining the reason certain soil environments are more prone to losing nitrogen than others, the Whalen lab has found that manure and inorganic sources are cycled through the soil biomass quite rapidly. This has resulted in a very significant amount of nitrogen runoff, and nitrogen loss to the atmosphere.

The lab also utilizes the earthworm to study nutrient cycles. Earthworms create a habitat suited to microbial nitrifiers (microorganisms that oxidize an ammonia compound in nitrates and nitrites) and denitrifiers (microorganisms that convert nitrogen oxides such as nitrous oxide to molecular nitrogen). This is valuable because testing the nutrient flux of an area provides more practically useful information for developing precise farming and land management techniques than testing nitrogen composition in isolation.
The lab also looks at a number of other soil-related environmental issues such as the toxicity of nanoparticles and the economic benefits of temperate tree-based intercropping systems. With their research, the Whalen lab hopes to find ways to make fertilizers more economically and environmentally efficient.