Location: Dairy Forage ResearchTitle: Chemistry and microbial functional diversity differences in biofuel crop and grassland soils in multiple geographies) Author
|Lee, E. Henry|
|Collins, Harold - Hal|
|Mitchell, Robert - Rob|
Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2012
Publication Date: 11/21/2012
Publication URL: http://handle.nal.usda.gov/10113/62416
Citation: Watrud, L., Reichman, J., Bollman, M., Smith, B., Lee, E., Jastrow, J., Casler, M.D., Collins, H.P., Fransen, S., Mitchell, R., Owens, V.N., Bean, B., Rooney, W.L., Tyler, D.D., King, G.A. 2012. Chemistry and microbial functional diversity differences in biofuel crop and grassland soils in multiple geographies. BioEnergy Research. 6(2):601-619. Interpretive Summary: As crop and non-crop lands are increasingly becoming converted to biofuel feedstock production it is important to identify potential impacts of annual and perennial feedstocks on soil health. We compared sorghum (annual) and switchgrass (perennial) biofuel crop soils to nearby non-cropland soils. The non-croplands included tallgrass prairies or oak savannahs in Illinois, Wisconsin, Nebraska, and South Dakota; short grass prairie in Texas; and sagebrush steppe in Washington. We measured microbial gene diversity in soil samples as a potential indicator of soil health under the assumption that more diverse microbial communities lead to healthier soils in the long term. Sorghum crop soils had lower microbial gene diversity than nearby non-cropland soils. Sorghum sites had a more narrow range of microbial gene diversity than the switchgrass sites. Microbial gene diversity at switchgrass sites varied between geographic locations, but not with land use type. A perennial biofuel crop, such as switchgrass, appears to maintain naturally diverse microbial communities better than an annual such as sorghum. This kind of information should be useful to land managers and policy makers involved in the development of a bio-based energy economy.
Technical Abstract: As crop and non-crop lands are increasingly becoming converted to biofuel feedstock production, it is of interest to identify potential impacts of annual and perennial feedstocks on soil ecosystem services. Soil samples obtained from 6 regional sets of switchgrass (Panicum virgatum L.) and 3 regional sets of sorghum (Sorghum bicolor L.) crop and nearby non-crop grassland locations were analyzed for chemical characteristics, microbial gene diversity and abundance, active microbial biomass and nematode diversity. Sorghum crop and non-crop sites differed significantly from switchgrass sites with regard to soil chemistry; i.e., sorghum crop soils had significantly higher NO3-N, NH4-N, SO4-S, and Cu levels than non-crop soils. In contrast, few significant differences in soil chemistry were observed between switchgrass crop and non-crop soils. No significant differences were observed in nematode functional diversity or active fungal biomass between crop and non-crop soils; however, active bacterial biomass was significantly lower in sorghum soils than in switchgrass soils. Using GeoChip 4.0 functional gene arrays (FGA) to analyze soil DNA, microbial gene diversity was significantly lower in sorghum crop soils than in non-crop soils. Microbial gene diversity at switchgrass sites varied between geographic locations, but not with land use type. No significant differences in microbial gene abundance were observed between sorghum crop and non-crop soil samples. However, microbial gene abundance in switchgrass crop soil samples was significantly lower than in non-crop soils. Gene diversity at sorghum locations was significantly correlated with pH, NO3-N, NH4-N and % silt in the majority of 15 FGA categories. Gene abundance at switchgrass locations was correlated with pH, Cu, Mn, Fe, % soil moisture, % sand, % silt, % clay and active bacterial biomass. Our results suggest that cultivation of a perennial biofuel crop such as switchgrass influences soil ecosystem services less than cultivation of an annual biofuel crop such as sorghum.