Farmers ask a lot of the land: feed people, provide power, produce fiber and retain nutrients in the soil so there' s no pollution of air and water. The effort will take more research and that's what the U.S. Department of Energy's Argonne National Laboratory is working on.
Working with the farming community of the Indiana Creek Watershed in Central Illinois, these researchers are finding ways to simultaneously meet three objectives: maximize a farmer's production, grow feedstock for bioenergy, and protect the environment. The researchers found that the three goals are not necessarily mutually exclusive.
The key is a "multifunctional landscape" where resources are "allocated efficiently and crops are situated in their ideal soil and landscape position," notes a release detailing the Argonne work. For example, planting bioenergy crops like willows or switchgrass in rows where commodity crops are challenged - that provides an energy feedstock while also limiting fertilizer runoff into waterways.
Cristina Negri, principal agronomist and environmental engineer, Argonne, explains: "The issue we're working to address is how to design bioenergy systems that are sustainable. It's not idealistic. We wanted to show that its doable, if we design for specific outcomes, we'll see real results."
Negri and her team created a pilot farm site aiming to balance the priorities of economic feasibility, bioenergy and environmental health. The team found that to meet the challenge they needed a change in perspective. They divided the field into subareas and found those with lowest yield had the lowest nitrogen retention. These seconds of land are double-taxing - unprofitable and potentially harmful to the environment.
Says Negri: "Imaging pouring a nice, nutrient-rich solution through a fertile soil with plants growing in it." She says the plants would retain the nutrients with their root systems. "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 heads for 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. 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.
While scientists may be invested in energy and environment, the team recognized that farmers — the true agents of change — have to think first and foremost about their economic bottom line.
“Across the entire field your farm might be profitable, but by collecting more specific data we can identify subareas where the farmer is not recovering his or her investment,” said Argonne postdoctoral researcher Herbert Ssegane.
The money lost comes from farmers cropping and applying expensive nitrogen fertilizers to patches of the field that are just not producing enough. Inserting rows of bioenergy crops where there is low corn yield means the farmer is not sacrificing substantial profit from row crops. As a cost-saving bonus, the deep-rooted bioenergy crops naturally accumulate the lost nitrogen as a free fertilizer.
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.
The scientists are exploring how these design principles can be scaled up to the entire watershed. Eventually, they hope this research informs agricultural planning for scientists and farmers alike.
“Multifunctional landscapes: Site characterization and field-scale design to incorporate biomass production into an agricultural system,” the most recent paper analyzing data from Fairbury, was published in the journal Biomass and Bioenergy. Funding for this research comes from the DOE’s Office of Energy Efficiency and Renewable Energy, Bioenergy Technologies Office.The Department of Energy’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.
Source: U.S. Department of Energy