Net global warming potential and greenhouse gas intensity in a double-cropping cereal rotation as affected by nitrogen and straw management

[摘要] The effects of nitrogen and straw management on global warming potential(GWP) and greenhouse gas intensity (GHGI) in a winter wheat–summer maizedouble-cropping system on the North China Plain were investigated. Wemeasured nitrous oxide (N₂O) emissions and studied net GWP (NGWP) andGHGI by calculating the net exchange of CO₂ equivalent(CO₂-eq) from greenhouse gas emissions, agricultural inputs andmanagement practices, as well as changes in soil organic carbon (SOC), based on along-term field experiment established in 2006. The field experiment includessix treatments with three fertilizer N levels (zero N (control), optimum andconventional N) and straw removal (i.e. N₀, N_opt andN_con) or return (i.e. SN₀, SN_opt andSN_con). Optimum N management (N_opt, SN_opt)saved roughly half of the fertilizer N compared to conventional agriculturalpractice (N_con, SN_con), with no significant effect ongrain yields. Annual mean N₂O emissions reached 3.90 kgN₂O-N ha⁻¹ in N_con and SN_con, and N₂Oemissions were reduced by 46.9% by optimizing N management ofN_opt and SN_opt. Straw return increased annual meanN₂O emissions by 27.9%. Annual SOC sequestration was 0.40–1.44 MgC ha⁻¹ yr⁻¹ in plots with N application and/or straw return.Compared to the conventional N treatments the optimum N treatments reducedNGWP by 51%, comprising 25% from decreasing N₂O emissions and75% from reducing N fertilizer application rates. Straw returntreatments reduced NGWP by 30% compared to no straw return because theGWP from increments of SOC offset the GWP from higher emissions of N₂O,N fertilizer and fuel after straw return. The GHGI trends from the differentnitrogen and straw management practices were similar to the NGWP. Inconclusion, optimum N and straw return significantly reduced NGWP and GHGIand concomitantly achieved relatively high grain yields in this importantwinter wheat–summer maize double-cropping system.

[学科分类] 地球化学与岩石