The researchers found that the perennial crops quickly reduced nitrate leaching in the mid-soil profile as well as from tile lines. "By year four each of the perennial crops had small losses," Smith said. "Nitrous oxide emissions also were much smaller in the perennial crops--including switchgrass, which was fertilized with nitrogen, while prairie and miscanthus were not. Overall, nitrogen levels were higher for the corn and soybean treatment as well as switchgrass, but were lower for prairie and miscanthus. Prairie and miscanthus levels were lower due to harvest of the plant biomass (and nitrogen) each winter, with no fertilizer nitrogen additions to replace it, as occurred in corn and switchgrass," she said.
David added that the miscanthus and mixed prairie also had very wide carbon-to-nitrogen ratios in the harvested material -- as much as 257 to 1 for miscanthus. "Miscanthus efficiently moved nitrogen from leaves to root and rhizome systems after the growing season, where it could be used again the next year," David said. "The lower nitrogen level suggests that the small amount of nitrogen removed by harvest in prairie and miscanthus came from the large pool of soil nitrogen and/or nitrogen fixation. If the soil is the source, this could lead to depletion of this resource without fertilization. If microbial fixation supplied the nitrogen, this would be a more sustainable input," he said.
David said that although more research is needed to fully understand the nitrogen cycle in these new and exciting biofuel crops such as miscanthus, results from this study clearly show these crops have the potential to quickly and greatly reduce nitrogen losses that have important environmental effects, while providing a large biomass harvest.'/>"/>
|Contact: Debra Levey Larson |
University of Illinois College of Agricultural, Consumer and Environmental Sciences