|Ontl, Todd -|
|Hofmockel, Kirsten -|
|Schulte, Lisa -|
|Kolka, Randall -|
Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 31, 2013
Publication Date: August 1, 2013
Citation: Ontl, T.A., Hofmockel, K.S., Cambardella, C.A., Schulte, L.A., Kolka, R.K. 2013. Topographic and soil influences on root productivity of three bioenergy cropping systems. New Phytologist. 199(3):727-737. DOI:10.1111/nph.12302. Interpretive Summary: Agricultural management may substantially influence regional carbon (C) cycling, particularly with anticipated shifts to cellulosic bioenergy production, including switchgrass, in the north central Midwest. Carbon cycling is also influenced by topography, through spatial variation in soil properties which can influence belowground ecological processes, including C distribution into soil organic matter and into roots. This study provides field data on the response of root production of bioenergy crops planted across a topographic gradient. Our results show that root productivity did not differ across landscape positions in corn and sorghum-triticale bioenergy cropping systems, although switchgrass root production was impacted by location on the landscape. We found that switchgrass root production was greater in heavier soils with higher sand contents. Using available variables, such as soil texture, delineated in geospatial soil databases may aid in predicting root productivity of perennial bioenergy crops. These results will provide information to land managers for development and implementation of cellulosic bioenergy production systems.
Technical Abstract: Successful modeling of the carbon (C) cycle requires empirical data regarding species-specific root responses to edaphic characteristics. We address this challenge by quantifying annual root production of three bioenergy cropping systems (continuous corn, sorghum-triticale, switchgrass) arrayed across a toposequence within a Midwestern agroecosystem. Using ingrowth cores to measure species-specific responses in root production, we tested for the effects of topography and 11 soil characteristics on root productivity. Root production significantly differed among all cropping systems. Topography had distinct impacts on switchgrass root productivity, but did not significantly influence root productivity of annual crops. High switchgrass root production was associated with low soil C and nitrogen levels, and high percent sand and bulk density. Percent sand content was the best predictor of switchgrass root production, explaining 44% of the variation. Our results suggest that crop type can be used as a predictor of root productivity and easily measured soil parameters can be used to improve model predictions of bioenergy switchgrass root productivity, but the soil factors we measured cannot be used to predict root productivity in annual cropping systems. These results can improve C cycle modeling efforts by revealing the influence of cropping system and topography on root productivity.