Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/25/2016
Publication Date: N/A
Technical Abstract: Perennial grasses like switchgrass or big bluestem when managed as bioenergy feedstock require nitrogenous inputs. Nitrogen fertilizer frequently cause nitrous oxide emission. Therefore, managing grasses as feedstock may reduce the greenhouse gas (GHG) mitigation potential expected from perennial. Few studies have measured N2O emission from perennial grasses managed as feedstock. The objectives of this study were to compare GHG emission and mitigation by via sequestering soil organic carbon between 1) grasses with legume companion crop or with nitrogenous fertilizer, 2) two grass harvest times (Autumn, Spring), and 3) perennial systems and corn (Zea maize L.)/soybean (Glycine max) (C/S) rotation, all without tillage. Nitrous oxide flux was measured from for three years and SOC was measured in three times over the course of eleven years. Both grass species grown with a legume companion had dramatically reduced annual N2O emission and yield-scaled emission compared to their respective urea fertilized counterpart. Harvest timing also impacted cumulative N2O emission, such that there was 14 to 40% greater emission when harvest was delayed until spring compared to harvesting the grasses in autumn following a killing frost. Unexpectedly, emission from the fertilized grassed exceeded that of C/S rotation/ Emission factor for fertilized grasses averaged 2.5%, corn averaged 1.05%. Carbon stored under the grasses was measurable only in the soil surface, and may not may not be adequate to offset fertilizer induced N2O emission. Best nitrogen management is recommended for herbaceous perennials to optimize biomass production but minimize N2O emission.