Converging Paths

With the global population projected to hit 8.5 billion by 2030, we face a daunting challenge: feeding the world while remaining ecologically responsible. According to the United Nations, this estimated population growth reflects the addition of 1.2 billion people over 30 years. Faced with these rising numbers, how will we meet the increased demand for food?

Farmers, for one, will play a critical role as they strive to produce high-yielding crops. Making this possible, however, requires the use of fertilizers and pesticides, which can have adverse effects — from harming pollinators to increasing greenhouse gases that cause climate change.

Sylvie Brouder, a professor in Purdue’s Department of Agronomy, seeks to help farmers gain the most from their fields while reducing potential environmental harm. Her work explores carbon and nitrogen cycling in soil, carbon sequestration, greenhouse-gas emissions and water-quality impacts of farming.

“We’ll never have a single solution to the sustainability problem. It isn’t just about one nutrient or crop because these are agricultural systems, and they always change,” Brouder says. “There will always be new challenges, and there will always be tradeoffs. You work to understand those tradeoffs, and society will decide which are acceptable.”

Brouder’s research has led to the development of nutrient management guides and technologies that help reduce greenhouse-gas emissions and improve air and water quality. They do so by balancing the amount of nitrogen and other fertilizers applied to fields with that taken up by plants or added to the organic nitrogen reserves of healthy soils. She also focuses on modifying tile drainage systems and crop rotations to keep nutrients from entering waterways.

As part of a project funded by the U.S. Department of Agriculture, Brouder is developing models to help farmers determine where they can use marginal lands to grow bioenergy crops. Winter cover crops such as cereal rye can reduce soil erosion and take up residual soil nitrogen to prevent it from leaching into streams and rivers.

The cover crop, however, has no direct economic value, and farmers often must kill it with chemicals before planting economic crops. That’s why Brouder and her colleagues are exploring novel systems that grow winter cover crops as harvestable bioenergy crops, keeping year-round cover on the soil.

“Farmers are encouraged to grow cover crops for their ability to protect the soil and improve water quality. However, cover cropping requires significant financial investments — seed and herbicides to kill the crop in the spring — with no direct economic return on activity,” she says. “We are exploring what happens to the soil-plant system when, instead of just returning the cover crop to the field as residue, the top growth is removed as a crop — in this case as a potential feedstock for cellulosic ethanol production.”

Win-win solutions like this should impact the work of state and federal policymakers, in addition to farmers. “We take advantage of any and all opportunities to educate these stakeholders in our findings so these individuals can, in turn, develop science-based policies to promote on-farm profitability in concert with environmental stewardship,” Brouder says.