N₂O and CH₄ emissions from soils under conventional and no-till management practices in Goiânia (Cerrados, Brazil)

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• 作者：Auré ; lie Metay ; Robert Oliver ; Eric Scopel ; Jean-Marie Douzet ; José ; Aloisio Alves Moreira ; Florent Maraux ; Brigitte J. Feigl ; Christian Feller
• 关键词：No tillage ; CH₄ ; N₂O ; Soil C sequestration ; Cerrado ; Brazil
• 刊名：Geoderma
• 出版年：2007
• 期刊代码：28_00167061
• 类别：ear
• 出版时间：15 September 2007
• 卷：141
• 期：1-2
• 页码：78-88
• 文件大小：407 K

摘要

Nitrous oxide (N₂O) and methane (CH₄) are important greenhouse gases (GHG) produced respectively by the naturally occurring microbial processes of incomplete denitrification or nitrification and methanogenesis. Tillage practices and climate affect the release of GHGs. No tillage (DMC) systems may increase CO₂–C fixation in soil but also N₂O and CH₄ emissions. The aim of this article is to question whether the positive effect of a DMC system observed on carbon storage for the topsoil layer in Cerrado soils is offset or not by the N₂O and/or CH₄ emissions. Two 5-year-old systems, tillage (disc on the first 15 cm called offset: OFF) and a direct-sowing mulch-based crop system (DMC) with an additional cover crop were studied during a cropping cycle. N₂O and CH₄ fluxes are determined using a closed-chamber, N₂O and CO₂ concentrations are measured at 3 depths (10-, 20- and 30 cm). No significant difference between treatments was observed for both gases (for emissions and concentrations). Soil N₂O contents increase from surface to depth (30 cm) and range from 300 ppbv to 3 ppm for both treatments. Total annual estimated emissions of N₂O range from 31 to 35 g N₂O–N ha^{− 1} year^{− 1} for DMC and OFF respectively which is low and corresponds only to 0.03%of the total N-fertilizer applied. Monthly means N₂O emissions were strongly correlated to monthly means of N₂O content at 10 cm depth (R² = 0.66) and seem to increase exponentially with monthly mean Water Filled Pore Space WFPS (0–10 cm layer) (R² = 0.33). CH₄ fluxes were very low as well: both treatment act as source of CH₄ (245 and 403 g CH₄–C ha^{− 1} year^{− 1} for DMC and OFF respectively. On a CO₂–C equivalent basis these results correspond to 4.1 and 4.7 kg CO₂–C ha^{− 1} year^{− 1} for N₂O and to 1.9 and 3.1 kg CO₂–C ha^{− 1} year^{− 1} for CH₄ for DMC and OFF respectively. As a result, the carbon sequestration balance taking into account the CO₂, CH₄ and N₂O on a CO₂–C equivalent basis is in favour of DMC treatment considering that this treatment increases carbon storage originated from CO₂–C for the topsoil (0–10 cm) layer (350 kg C ha^{− 1} year^{− 1}) in comparison with OFF treatment.