Location: Soil Management ResearchTitle: Does soil C accrual under perennial grasses managed for bioenergy offset fertilizer induced N2O emission?
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/25/2017
Publication Date: 10/25/2017
Citation: Johnson, J.M., Barbour, N.W. 2017. Does soil C accrual under perennial grasses managed for bioenergy offset fertilizer induced N2O emission? [Abstract]. ASA-CSSA-SSSA Annual Meeting Abstracts. ASA-CSSA-SSSA Annual Meeting. Oct. 22-25, 2017, Tampa, FL. Available: https://scisoc.confex.com/crops/2017am/webprogram/Paper105737.html.
Technical Abstract: Perennial grasses (e.g., switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerdardii Vitman) are often touted as being low input and as having a C-neutral foot print, but managing them as bioenergy feedstock means adding nitrogenous fertilizer or inter-cropping with legumes, which can increase emission of nitrous oxide (N2O). Increases in N2O emission may reduce greenhouse gas mitigation from soil organic carbon (SOC) accrual, which is anticipated by growing perennials instead of annuals. The objectives of this study were to compare SOC storage and N2O emission between 1) grasses with legume companion crop or with nitrogenous fertilizer, 2) two grass harvest times (Autumn, Spring), and 3) perennial systems and the a no till - corn (Zea maize L.)/soybean (Glycine max) (C/S) rotation with all residue returned. The study was conducted on an experimental site established in 2000. All crops were managed with recommended fertilizer rates. Soil was sampled for SOC in 2000, 2006 and 2011) and N2O flux was assessed between 2009 and 2012 using with closed-vented chambers. In perennial grasses, SOC accrual was only measured in the surface 0-5 cm, but in the no-till C/S rotation SOC declined. For both grasses, intercropping with a legume instead of adding nitrogen reduced annual and yield-scaled annual N2O emission compared to their respective counterpart. In the Spring treatment, which delayed grass harvest increased N2O emission 14 to 40% compared to Autumn harvest. Emission from the fertilized grasses exceeded that of C/S rotation, such that the emission factor was almost doubled from fertilized grasses compared to fertilized corn. It was concluded that SOC accrual by the grasses was not enough to compensate for the increase in N2O emission. Management strategies to improve SOC accrual, minimize N2O emission and enhance biomass production for bioenergy managed grasses are needed.