Dryland Soil Greenhouse Gas Emissions Influenced by Tillage, Cropping Sequence, and Nitrogen Fertilization

Management practices are needed to reduce greenhouse gas emissions from dryland agroecosystems. The effect of tillage, cropping sequence, and N fertilization on soil CO2, N2O, and CH4 fluxes was evaluated on a dryland loam soil from March to November, 2008 to 2010 in eastern Montana. Treatments were three cropping sequences [no-tilled continuous malt barley (NTCB), no-tilled malt barley-pea (NTB-P), and conventional-tilled malt barley-fallow (CTB-F)] and two N fertilization rates (0 and 80 kg N ha-1). The CO2 and N2O fluxes increased immediately following substantial precipitation during increased temperature in the summer from May to August. During this period, CO2 flux was greater in NTCB and NTB-P than in CTB-F and greater with 80 than with 0 kg N ha-1. The N2O flux varied with tillage and cropping sequence but was greater with 80 than with 0 kg N ha-1. Total CO2 flux from March to November was greater in NTCB than in CTB-F in all years and greater with 80 than with 0 kg N ha-1 in 2009 and 2010. Total N2O flux was not influenced by tillage, cropping sequence, and N fertilization. Both CO2 and N2O fluxes were greater in 2008 than in 2010. The CH4 flux remained negative at most measurement dates in all years. Increased root respiration and biomass production due to continuous cropping and N fertilization probably increased CO2 emissions under dryland cropping systems. Similarly, increased N availability probably increased N2O emissions during active crop growth. Increased soil water content due to greater rainfall probably increased CO2 and N2O emissions in 2008 than in 2010.