title: Initial nitrous oxide, carbon dioxide, and methane costs of converting conservation reserve program grassland to row crops under no-till vs. conventional tillage.
abstract: Around 4.4 million ha of land in USDA Conservation Reserve Program (CRP) contracts will expire between 2013 and 2018 and some will likely return to crop production. No-till (NT) management offers the potential to reduce the global warming costs of CO2 , CH4 , and N2 O emissions during CRP conversion, but to date there have been no CRP conversion tillage comparisons. In 2009, we converted portions of three 9-21 ha CRP fields in Michigan to conventional tillage (CT) or NT soybean production and reserved a fourth field for reference. Both CO2 and N2 O fluxes increased following herbicide application in all converted fields, but in the CT treatment substantial and immediate N2 O and CO2 fluxes occurred after tillage. For the initial 201-day conversion period, average daily N2 O fluxes (g N2 O-N ha(-1)  d(-1) ) were significantly different in the order: CT (47.5 ± 6.31, n = 6) ≫ NT (16.7 ± 2.45, n = 6) ≫ reference (2.51 ± 0.73, n = 4). Similarly, soil CO2 fluxes in CT were 1.2 times those in NT and 3.1 times those in the unconverted CRP reference field. All treatments were minor sinks for CH4 (-0.69 ± 0.42 to -1.86 ± 0.37 g CH4 -C ha(-1)  d(-1) ) with no significant differences among treatments. The positive global warming impact (GWI) of converted soybean fields under both CT (11.5 Mg CO2 e ha(-1) ) and NT (2.87 Mg CO2 e ha(-1) ) was in contrast to the negative GWI of the unconverted reference field (-3.5 Mg CO2 e ha(-1) ) with on-going greenhouse gas (GHG) mitigation. N2 O contributed 39.3% and 55.0% of the GWI under CT and NT systems with the remainder contributed by CO2 (60.7% and 45.0%, respectively). Including foregone mitigation, we conclude that NT management can reduce GHG costs by ~60% compared to CT during initial CRP conversion.
authors.affiliation: Department of Plant, Soil and Microbial Sciences, Michigan State University, Hickory Corners, MI 49060, USA. ruanleil@msu.edu
authors.forename: Leilei
authors.initials: L
authors.lastname: Ruan
authors.forename: G
authors.initials: G
authors.lastname: Philip Robertson
mesh_terms: D000383:Agriculture / Q000191:economics / Q000379:methods*; D002245:Carbon Dioxide / Q000378:metabolism*; D003247:Conservation of Natural Resources / Q000379:methods*; D018556:Crops, Agricultural / Q000254:growth & development; D017752:Greenhouse Effect / Q000191:economics / Q000517:prevention & control*; D008697:Methane / Q000378:metabolism*; D008824:Michigan; D009609:Nitrous Oxide / Q000378:metabolism*
chemical_list: D002245:Carbon Dioxide; D009609:Nitrous Oxide; D008697:Methane
keywords: carbon dioxide; conservation reserve program; global warming impact; greenhouse gas balance; methane; nitrous oxide; no-till; tillage
references.citation: Environ Manage. 2009 Oct;44(4):732-44
references.pmid: 19707705
references.citation: Glob Chang Biol. 2013 Jan;19(1):33-44
references.pmid: 23504719
references.citation: Proc Natl Acad Sci U S A. 2011 Aug 16;108(33):13864-9
references.pmid: 21825117
references.citation: Science. 2000 Sep 15;289(5486):1922-5
references.pmid: 10988070
references.citation: J Environ Qual. 2009 Aug 24;38(5):2023-33
references.pmid: 19704145