Location: Soil, Water & Air Resources ResearchTitle: Partitioning carbon fluxes from a Midwestern corn and soybean rotation system using footprint analysis
|DOLD, CHRISTIAN - Orise Fellow|
|WACHA, KENNETH - Orise Fellow|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/15/2017
Publication Date: 12/15/2017
Citation: Dold, C., Hatfield, J.L., Prueger, J.H., Wacha, K.M. 2017. Partitioning carbon fluxes from a Midwestern corn and soybean rotation system using footprint analysis. In: Proceedings of American Geophysical Union Fall Meeting, December 11-15, 2017, New Orleans, LA.
Technical Abstract: Midwestern US agriculture is dominated by corn and soybean production. Corn has typically higher Net Ecosystem Exchange (NEE, that is the annual sum of CO2 fluxes, the total carbon uptake minus total carbon respired by the plants-soil-ecosystem) than soybean due to increased carbon uptake efficiency and different crop management. The NEE may be measured with eddy covariance (EC) stations covering both crops, however, it is often unclear what the contribution of each crop is, as the CO2 source area (or footprint), where the measured CO2 flux originates, remains uncertain. The aim of this study was to quantify the contribution of CO2 fluxes from each crop for a conventional corn-soybean rotation system from 2007–2015. Therefore, the combined CO2 flux of three adjacent fields with annual corn-soybean rotation was measured with a 9.1 m EC tower (Flux 30). In the center of two of these fields, additional EC towers (Flux 10 and Flux 11) were positioned above the corn and soybean canopy to validate Flux 30 NEE. For each EC system the annual 90% NEE source area was calculated, footprints were partitioned among fields, and NEE separated accordingly. The average annual 90% footprint area of Flux 30, and Flux 10/11 corn and soybean was estimated 206, 11 and 7 hectare, respectively. The annual average NEE of Flux 30 was -693 g CO2 per square meter and year, of which 83% out of 90% originated from the three adjacent fields. Corn and soybean NEE measured at Flux 10 and 11 was -1124 and 173 g CO2 per square meter and year, respectively, and 89% and 90% originated from these fields. This indicates that Flux 30 represents the combined NEE of a corn-soybean rotation, and Flux 10 and 11 measured NEE from a single crop. However, the share of Flux 30 NEE originating from corn and soybean grown on the Flux 10/11 fields was -192 and -205 CO2 per square meter and year, indicating a substantial difference to single crop NEE. While it was possible to measure the NEE of a corn-soybean rotation, footprint partitioning could not retrieve single crop NEE, probably due to differences in measurement height and footprint source area.