Straw amendment with nitrate-N decreased N2O/(N2O+N2) ratio but increased soil N2O emission: A case study of direct soil-born N2 measurements
Straw amendment with nitrate-N decreased N2O/(N2O+N2) ratio but increased soil N2O emission: A case study of direct soil-born N2 measurements
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DOI：
10.1016/j.soilbio.2018.10.002
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发表时间：
2018-12
影响因子：
9.7
通讯作者：
Di Wu;Zhijun Wei;R. Well;J. Shan;Xiaoyuan Yan;R. Bol;M. Senbayram
中科院分区：
文献类型：
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作者：
Di Wu;Zhijun Wei;R. Well;J. Shan;Xiaoyuan Yan;R. Bol;M. Senbayram
秸秆与合成氮肥配施可提高作物产量和土壤肥力，但秸秆对土壤N2O排放的影响一直存在矛盾的观察结果。秸秆施用可以影响反硝化速率及其产物化学计量（N2O/(N2O + N2)比），而后者尚不清楚，因为该比率受其他土壤参数的强烈调节，例如反硝化微位点的硝酸盐和氧浓度。在此背景下，我们在He/ o2气氛下使用机器人连续流培养系统进行了培养实验，并测量了22天内N2O和直接N2O通量。在85%充满水的孔隙空间下，施用和不施用水稻秸秆的土壤（2.5 g kg−1soil）与施用硝酸钾（10 mM KNO3）的对照土壤和未施用秸秆的对照土壤进行培养。为了模拟短时间的土壤缺氧，设置了三种不同的o2分压相（20%、5%和10%）。此外，分析了土壤排放N2O的N2O位点偏好特征，以确定对N2O通量有贡献的过程。与未施肥对照相比，添加硝酸盐增加了累积N2O通量，减少了累积n2通量，而与仅施用硝酸盐相比，水稻秸秆改良显著增加了N2O和n2排放量。各处理N2O SP值在0.4 ~ 2.7‰之间，表明反硝化/硝化剂反硝化是主要来源。结果表明，秸秆还原剂能提高反硝化速率，而秸秆还原剂对N2O排放量和N2O/(N2O + N2)产物比的影响强烈依赖于土壤NO3−浓度。综上所述，在有利于反硝化作用的条件下，秸秆改良与硝态氮结合可以增加土壤N2O排放，尽管它可能降低总体N2O/(N2O + N2)产物比。
Straw application in combination with synthetic N fertilizer could increase crop yield and improve soil fertility, however, contradictory observations have been reported on the effects of straw addition on soil N2O emission. Straw application can affect both denitrification rate and its product stoichiometry (N2O/(N2O + N2) ratio), whereas the latter remains rather unclear since the ratio is strongly regulated by other soil parameters, e.g. nitrate and oxygen concentrations at denitrifying micro-sites. In this context, we conducted an incubation experiment with a robotized continuous flow incubation system using a He/O2atmosphere and measured N2O and direct N2fluxes over 22 days. Soil amended with and without rice straw (2.5 g kg−1soil) in conjunction with nitrate fertilizer (10 mM KNO3) and non-amended control soil were incubated under 85% water-filled pore space. To simulate a short soil anoxic period, three different O2partial pressures phases were set (20%, 5% and 10%). Additionally, N2O site preference signatures of soil-emitted N2O were analyzed to identify the processes contributing to N2O fluxes. Addition of nitrate increased cumulative N2O fluxes and decreased cumulative N2fluxes compared with non-fertilized control, while rice straw amendment increased both N2O and N2emissions drastically compared with the nitrate only treatment. The N2O SP values ranged from 0.4 to 2.7‰ among all treatments, indicating denitrification/nitrifier denitrification was the dominating source. The results suggest that straw amendment can trigger high denitrification rate, whereas the effect of straw amendment on the amount of emitted N2O and the N2O/(N2O + N2) product ratio strongly depends on soil NO3−concentration. As a conclusion, the present study suggests that straw amendment in conjunction with nitrate-N can increase soil N2O emissions under conditions favoring denitrification, even though it may decrease the overall N2O/(N2O + N2) product ratio.