[font face=Serif][font size=5]Scientists study ways to integrate biofuels and food crops on farms[/font]

By Payal Marathe • July 7, 2015

[font size=3]We ask a lot of the land: feed the world with crops, power the world with bioenergy, retain nutrients so they don’t pollute our water and air. To help landscapes answer these high demands, scientists from the U.S. Department of Energy’s Argonne National Laboratory are designing ways to improve—and hopefully optimize—land use.

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Meeting this challenge called for a change in perspective. Rather than looking at whole fields as the unit of planting decisions, researchers analyzed subareas of the cornfield. They found that subareas with the lowest yield also had the lowest nitrogen retention. These sections of land are doubly taxing — unprofitable for the farmer and damaging to the environment.

Negri explained what happens in the underproductive land: “Imagine pouring a nice, nutrient-rich solution through a fertile soil with plants growing in it,” she said. These nutrients would be retained by the soil long enough to be taken up by plants, minimizing any leakage. “Now imagine pouring this same solution through a colander: If nutrients filter through the soil too quickly, they’re no longer available for plants. The corn grows less, and more nitrogen is leached into groundwater.”

But planting bioenergy crops in the colander-like soil could solve both problems — environmental and economic — as the Argonne team showed with the Denitrification Decomposition simulation.

Willows and switchgrass are perennial bioenergy crops, meaning their life cycle spans multiple years. These plants have a more extensive root system than annual plants, which start their growth from scratch every year. Deeper roots are better able to absorb nitrogen as it seeps deeper into the soil.

The loss of nitrogen from agricultural land is a major environmental concern. If not retained by soil or taken up by plants, nitrogen escapes into air or water. It is released into the atmosphere as nitrous oxide, a greenhouse gas with 310 times the warming potential of carbon dioxide. Nitrate leaking into water spurs oxygen depletion that harms aquatic ecosystems and can lead to toxic algal blooms, as seen in Lake Erie. The Fairbury cornfield is located within the Indian Creek Watershed, draining to the Vermilion River and eventually to the Gulf of Mexico, which for years has been suffering from oxygen depletion caused by nutrient runoff.

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Argonne scientists planted willows at the Fairbury site in 2013 and will continue collecting data through next year to see how results compare to their predictions. “We’ve already reached a 28 percent reduction in nitrate, even with two full growing seasons still ahead of us,” Ssegane said. Willow growth has also been good, without the researchers applying any fertilizer.

According to Ssegane, this project is about proving a concept. It shows farmers that strategic planting of bioenergy crops can increase productivity and save money, while demonstrating to the scientific community that bioenergy will be sustainable if we match plants to their optimal position within a landscape.

“Before this work, the popular idea was ‘dedicated fields,’ where you might convert a large area from corn to switchgrass,” Ssegane said. “But dedicated fields of bioenergy crops are currently inviable in an agricultural setting where the economy is tied to grain. What does pass the cost-benefit test is converting underproductive subareas to an alternative crop.”

A multifunctional landscape finds the happy, efficient medium between a dedicated bioenergy field and a farm growing continuous acres of the same cash crop.

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