Location: Agroecosystem Management ResearchTitle: Management controls the net greenhouse gas outcomes of growing bioenergy feedstocks on marginally productive croplands
|Mitchell, Robert - Rob|
|KIMBLE, JOHN - Natural Resources Conservation Service (NRCS, USDA)|
Submitted to: Science Advances
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2019
Publication Date: 12/18/2019
Citation: Jin, V.L., Schmer, M.R., Stewart, C.E., Mitchell, R., Williams, C.O., Wienhold, B.J., Varvel, G.E., Follett, R.F., Vogel, K.P., Kimble, J. 2019. Management controls the net greenhouse gas outcomes of growing bioenergy feedstocks on marginally productive croplands. Science Advances. 5(12):1-6. https://doi.org/10.1126/sciadv.aav9318.
Interpretive Summary: Renewable energy from biomass plays a significant role in limiting global warming, and management decisions are key to biofuel sustainability. Although many modeling studies have evaluated the impact of biofuel production systems, field-based data is required to ground-truth simulated outcomes. Our research incorporated measured soil organic carbon changes, field-scale biomass yields, and direct greenhouse gas (GHG) emissions from agricultural soils from one of the longest running systems-level field experiments conducted at an operationally-relevant management scale. We show that long-term switchgrass (Panicum virgatum L.) systems are greenhouse gas (GHG) sinks and have greater climate mitigation potential than continuous corn (Zea mays L.) systems, which are GHG neutral. Our findings confer greater management flexibility in the selection of crops to use on marginally-productive landscapes. Using conservation practices (i.e. no-till) and rotating annual and perennial systems could provide near-term GHG-neutral options, with stronger longer-term climate mitigation possibilities when cellulosic feedstocks become a viable revenue source for producers.
Technical Abstract: Bio-based energy is key to developing a globally sustainable low-carbon economy. Lignocellulosic feedstock production on marginally productive croplands is expected to provide substantial climate mitigation benefits, but long-term field research comparing greenhouse gas (GHG) outcomes during the production of annual versus perennial crop-based feedstocks is lacking. Here, we show that long-term (16 years) switchgrass (Panicum virgatum L.) systems mitigate GHG emissions during the feedstock production phase compared to GHG-neutral continuous corn (Zea mays L.) under conservation management on marginally productive cropland. Increased soil organic carbon was the major GHG sink in all feedstock systems, but net agronomic GHG outcomes hinged on soil nitrous oxide emissions controlled by nitrogen (N) fertilizer rate. This long-term field study is the first to demonstrate that annual crop and perennial grass systems respectively maintain or mitigate atmospheric GHG contributions during the agronomic phase of bioenergy production, providing flexibility for land-use decisions on marginally productive croplands.