ARS | Publication request: Dryland soil greenhouse gas emissions affected by cropping sequence and nitrogen fertilization

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 18, 2012
Publication Date: September 12, 2012
Repository URL: http://handle.nal.usda.gov/10113/56099
Citation: Sainju, U.M., Caesar, T., Lenssen, A.W., Barsotti, J.L. 2012. Dryland soil greenhouse gas emissions affected by cropping sequence and nitrogen fertilization. Soil Science Society of America Journal. 76(5):1741-1757.

Interpretive Summary: Agricultural practices contribute about 6% of the total greenhouse gas (CO2, N2O, and CH4) emissions in U.S. The amount of CO2 and N2O emissions contributed by agriculture account for about 25 and 70%, respectively, of the total anthropogenic emissions. Fossil fuel consumption, land conversion to cropland, lime application, and N fertilization are major sources of agriculture CO2 emissions while soil management practices contribute about 92% of the total N2O emissions. Enteric fermentation and manure management account for 96% of the total CH4 emissions from agriculture. Although emitted in small amounts, N2O and CH4 are considered as potent GHGs because of their greater global warming potential (298 and 25 times, respectively, more powerful than CO2). Little information is available about the effects of soil and crop management practices on greenhouse gas emissions. We quantified the effects of tillage and cropping sequence combination and N fertilization on dryland soil temperature and water content at the 0- to 15-cm depth and CO2, N2O, and CH4 fluxes in a Williams loam in eastern Montana. Treatments were no-tilled continuous malt barley (NTCB), no-tilled malt barley-pea (NTB-P), and conventional-tilled malt barley-fallow (CTB-F), each with 0 and 80 kg N ha-1. Soil temperature varied but water content was greater in CTB-F than in other treatments. The greenhouse gas fluxes varied with date of sampling, peaking immediately after substantial precipitation (>15 mm) and N fertilization during increased soil temperature. Total CO2 flux from March to November was greater in NTCB or NTB-P with 80 kg N ha-1 than in other treatments from 2008 to 2010. Total N2O flux was greater in NTCB with 0 kg N ha-1 or in NTB-P with 80 kg N ha-1 than in other treatments in 2008 and 2011. Total CH4 uptake was greater with 80 than with 0 kg N ha-1 in NTCB in 2009 and 2011. Mean CO2 flux was 16% greater in NTC-B and NTB-P than in CTB-F and 7% greater with N fertilization than without. Because of intermediate level of greenhouse gas emissions and known favorable effect on malt barley yield, NTB-P with 0 kg N ha-1 might sustain greenhouse gas emissions and crop yields compared to other treatments in eastern Montana. For accounting global warming potential of management practices, however, additional information on soil C dynamics and CO2 associated with production inputs and machinery use are needed.

Technical Abstract: Information is needed to mitigate dryland soil greenhouse gas (GHG) emissions by using improved management practices. We quantified the effects of tillage and cropping sequence combination and N fertilization on dryland soil temperature and water content at the 0- to 15-cm depth and CO2, N2O, and CH4 fluxes in a Williams loam in eastern Montana. Treatments were no-tilled continuous malt barley (Hordeum vulgaris L.) (NTCB), no-tilled malt barley-pea (Pisum sativum L.) (NTB-P), and conventional-tilled malt barley-fallow (CTB-F), each with 0 and 80 kg N ha-1. Gas fluxes were measured at 3 to 14 d intervals using static, vented chambers from March to November, 2008 to 2011. Soil temperature varied but water content was greater in CTB-F than in other treatments. The GHG fluxes varied with date of sampling, peaking immediately after substantial precipitation (>15 mm) and N fertilization during increased soil temperature. Total CO2 flux from March to November was greater in NTCB or NTB-P with 80 kg N ha-1 than in other treatments from 2008 to 2010. Total N2O flux was greater in NTCB with 0 kg N ha-1 or in NTB-P with 80 kg N ha-1 than in other treatments in 2008 and 2011. Total CH4 uptake was greater with 80 than with 0 kg N ha-1 in NTCB in 2009 and 2011. Mean CO2 flux was 16% greater in NTC-B and NTB-P than in CTB-F and 7% greater with N fertilization than without. Because of intermediate level of GHG emissions and known favorable effect on malt barley yield, NTB-P with 0 kg N ha-1 might sustain GHG emissions and crop yields compared to other treatments in eastern Montana. For accounting global warming potential of management practices, however, additional information on soil C dynamics and CO2 associated with production inputs and machinery use are needed (GRACEnet Publication).