ARS | Publication request: Soil microbial activity under different grass species: Underground impacts of biofuel cropping

Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 2010
Publication Date: December 15, 2010
Citation: Haney, R.L., Kiniry, J.R., Johnson, M. 2010. Soil microbial activity under different grass species: Underground impacts of biofuel cropping. Agriculture, Ecosystems and Environment. 139(4):754-758.

Interpretive Summary: This paper shows that native grasses incorporate a great deal more carbon into soil than conventional farming. The study was primarily focused on the effect of different grass species and conventional corn on soil microbes. The study found that soil microbes are much more active under native grass species than conventional farming practices. Increased soil microbial activity is a healthy sign in terms of increased soil quality. This research has broad implications on our ability to manage climate change by using native grass species when and where appropriate. In addition it provides baseline data for conversion of cropping systems to native grass biofuel production for Blackland soils in central Texas.

Technical Abstract: Microbial and plant communities interact to determine local nutrient cycling rates. As lands are converted to bioenergy crops, including corn and cellulosic grasses, focus has been on changes in soil carbon sequestration. Little attention has been paid to impacts of such land conversion on the activity of belowground communities. We hypothesized that in addition to affecting soil organic carbon (SOC), monoculture species establishments have appreciable effects on microbial community activity, as evidenced by N and C mineralization rates. We compared soil microbial response in soils under long-term corn (Zea mays L.) production to soils under ten-year old monocultures of four warm-season perennial grasses (switchgrass (Panicum virgatum L.), coastal bermudagrass [Cynodon dactylon (L) Pers.], sideoats grama [Bouteloua curtipendula (Michaux) Torrey] and buffalo grass [Bouteloua dactyloides (Nutt.) Columbus]). All assayed perennial systems had higher SOC and water extractable organic C (WEOC) than the annual corn system. However, of all the perennial grasses, switchgrass soils had the lowest SOC and WEOC values, the highest 28 day mineralization C: N ratio, and the lowest 28 day C and N mineralization rates. This study indicates that microbial communities under switchgrass stands are more active than those under sideoats grama, buffalograss, coastal bermudagrass, or corn.