Comparison of Biofuel Cropping Systems (COBS)
Title: Comparison of Biofuel Cropping Systems (COBS)
Time Period: 2008-present
Research Team: Michael Thompson, Matt Helmers, Matt Liebman, and Robert Horton
Project Description: The experiment is large-scale (24 plots, each 27 m x 61 m, four replications of each system) and compares biomass production, fossil fuel replacement value, and environmental impacts for continuous corn grown for grain and stover removal with (CCW) and without (CC) a rye cover crop; multi-species perennial crops grown for aboveground biomass with (PF) and without (P) fertilizer; and a conventional corn-soybean grain system, used as a comparison baseline.
Twelve aluminum culverts were buried vertically at the ends of the center drainage lines from pairs of individual plots. Drainage lines from the plots are directed to sumps in the culvert, and drainage is pumped through plastic plumbing fitted with a plated sprayer nozzle and a water meter. Back pressure created by the meter forces a constant fraction (~0.25%) of all drainage to be diverted to a 10-L sampling bottle. The in-line flow meter is read when water samples are taken, and the system is also set up for continuous logging of the flow meters through switch-closure logging. This configuration provides the infrastructure for continuously monitored flow-volume measurements and flow-integrated sampling of subsurface drainage from each plot.
Drainage water samples have been collected weekly from the outlets of each plot during flow periods. Concentrations and loads of nitrate (NO3-N) and phosphate (PO4-P) were determined. Drainage water samples collected from the PF and P cropping systems had the lowest flow weighted mean concentration and load of NO3-N, which means the prairie cropping systems substantially limited the leaching of NO3-N even when the prairie received nitrogen fertilizers. Additionally, the continuous corn system with cover crops had lower nitrate-N concentration and load than the continuous corn system with no cover crop. Overall, the mass loss of PO4-P is quite low -- less than 0.14 kg/ha for all treatments.
Publications: Daigh, A.L.M., U. Ghosh, J. DeJong-Hughes, and R. Horton. 2018. Spatial response of near-surface soil water contents to newly imposed soil management. Agric. Environ. Lett. 3:180032. doi:10.2134/ael2018.06.0032.
Daigh, Aaron L. M., Xiaobo Zhou, Matthew J. Helmers, Carl H. Pederson, Robert Horton, Meghann Jarchow and Matt Liebman. 2015. Subsurface drainage nitrate and total reactive phosphorus losses in bioenergy-based prairies and corn systems. Journal of Environmental Quality 44:1638-1646.
Funders: Leopold Center for Sustainable Agriculture, Iowa Nutrient Research Center, Agronomy Department, ISU, College of Agriculture and Life Sciences, ISU
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