|NICHOLS, VIRGINIA - Washington State University|
|MIGUEZ, FERNANDO - Iowa State University|
|Sauer, Thomas - Tom|
|DIETZEL, RANAE - Iowa State University|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2016
Publication Date: 7/28/2016
Citation: Nichols, V.A., Miguez, F.E., Sauer, T.J., Dietzel, R.N. 2016. Maize and prairie root contributions to soil CO2 emissions in the field. Crop Science. 56:1-11. doi: 10.2135/cropsci2016.01.0048.
Interpretive Summary: Decomposition of organic matter like dead plants produces carbon dioxide, a greenhouse gas. Plant roots also emit carbon dioxide. When measuring carbon dioxide transport from soils, the gas can come from either of these sources. It is important to know how much carbon dioxide comes from each source so accurate estimates of net greenhouse gas production can be made. This research tested a new technique to separate the sources of carbon dioxide from soils. Prairie and crop sites were subjected to two different levels of shading from the sun. Shading reduced soil carbon dioxide transport and this reduction was attributed to lower root-derived carbon dioxide. The results of this study are of interest to scientists and land managers interested in improving estimates of greenhouse gas production.
Technical Abstract: Background and aims: A major hurdle in closing carbon budgets is partitioning soil-surface CO2 fluxes by source. This study aims to estimate CO2 resulting from root growth (RG) in the field. Methods: We used periodic 48-hour shading over two seasons to estimate and compare RG-derived CO2 in one annual and two perennial biofuel systems: continuously grown maize (CC) with grain and 50% stover harvest, unfertilized reconstructed tallgrass prairie (P), and the same prairie grown with spring nitrogen fertilization (PF), both with post-frost biomass harvest. Results in CC, P, and PF RG-derived CO2 contributed to 28, 31, and 30% of growing season cumulative CO2 emissions in 2012, and 19, 24, and 28% in 2013, respectively. Contrary to our hypothesis, total RG-derived CO2 flux was not proportional to end-of-season belowground biomass (BGB): P contained nearly twice the BGB of PF, but their cumulative RG-derived CO2 fluxes were not significantly different in either year. Conclusion: significant proportion of soil CO2 emissions is from root growth, making it a critical process to consider when comparing or modeling soil emissions of cropped or prairie soils. Unfortunately, BGB alone may not be a useful proxy for estimating root growth contributions.