中文关键词激发效应秸秆分解两源区分土壤CO₂¹³C标记C/N比 英文关键词rhizosphere effectsstraw decompositiontwo-source partitioning of soil CO₂¹³C labelingC/N ratio

作者	单位	E-mail
孙昭安	潍坊学院生物与农业工程学院, 山东省高校生物化学与分子生物学重点实验室, 潍坊 261061 中国农业大学资源与环境学院, 农田土壤污染防控与修复北京市重点实验室, 北京 100094	sun.zhaoan@163.com
张轩	中国农业大学资源与环境学院, 农田土壤污染防控与修复北京市重点实验室, 北京 100094
胡正江	山东省桓台县农业农村局, 桓台 256400
王开永	山东省桓台县农业农村局, 桓台 256400
陈清	中国农业大学资源与环境学院, 农田土壤污染防控与修复北京市重点实验室, 北京 100094
孟凡乔	中国农业大学资源与环境学院, 农田土壤污染防控与修复北京市重点实验室, 北京 100094	mengfq@cau.edu.cn

中文摘要 秸秆配施氮肥调节C/N比不仅影响外源秸秆的矿化，也影响内源土壤有机碳（SOC）的分解（即激发效应），因此研究秸秆与氮肥配比对土壤内外源有机碳分解的影响，对于农田温室气体减排和土壤肥力提升具有双重意义.本研究以山东桓台农田土壤为研究对象，为了探究秸秆与氮肥的配比对秸秆与SOC分解的影响，在不同氮肥水平下，采用¹³C标记玉米秸秆进行室内土壤培养32周，设置4个处理：CK、秸秆（S）、秸秆+低量尿素（SN1）和秸秆+高量尿素（SN2）.在整个培养期进行16次动态取样，借助¹³C两元线性模型，拆分土壤释放CO₂中源于秸秆和SOC的比例.结果表明，随着培养时间的进行，SOC分解对土壤释放CO₂的贡献呈先减少后升高的趋势，相反，秸秆矿化对土壤释放CO₂的贡献呈先升高后减少的趋势，到培养期末，SOC和秸秆分解对土壤CO₂释放的贡献分别为0.84~0.86和0.14~0.16；在整个培养期，施氮对秸秆累计分解的影响呈先增加后减少的趋势，高氮和低氮施用对秸秆分解的促进程度最高分别为15.8%和7.9%，经历整个培养期，低氮抑制秸秆幅度达到7.1%，而高氮呈轻度促进秸秆分解的趋势（0.7%）.在整个培养期，秸秆配施不同氮量对SOC矿化的激发效应程度呈先升高后降低趋势，在第7 d取样达到最高为55%~148%，并且随着施氮量增加而升高，随着培养时间的进行，各处理的激发效应程度趋于相等，约为50%.因此，秸秆配施氮肥调节C：N不仅影响外源秸秆对SOC的贡献，也影响内源SOC的分解，进而影响土壤碳的固持，经过整个培养期，土壤残留秸秆碳不能完全补偿因激发效应导致SOC的损失，导致SOC库的净亏损. 英文摘要 The adjustment of the C/N ratio by straw combined with fertilizer nitrogen (N) not only affects straw decomposition but also affects soil organic carbon (SOC) decomposition, i.e. the priming effects. Therefore, it is doubly important to study how the ratios of straw to N fertilizer influence the release of endogenous and exogenous C for greenhouse gas emission reduction and soil fertility improvement. We conducted a 32-week laboratory incubation experiment with ¹³C labeled maize straw under different N levels in farmland soil collected from fields in Huantai County to investigate the effect of the ratios of straw to N fertilizer on straw decomposition and the priming effects. Four treatments were set up, including CK, corn straw (S), corn straw+low urea rates (SN1), and corn straw+high urea rates (SN2). Dynamic sampling was conducted during the early stage (0-10 d), the middle stage (11-43 d), and the later stage (44-224 d) of straw decomposition. The approach was based on using a two-source mixing model to differentiate two sources of soil CO₂ (straw and soil-derived C). With an increase in the incubation time, the contribution of SOC decomposition to soil CO₂ emissions first decreased and then increased. On the contrary, the contribution of straw mineralization to soil CO₂ emissions first increased and then decreased. By the end of the incubation time, the contribution of SOC and straw decomposition to soil CO₂ emissions was 0.84-0.86 and 0.14-0.16, respectively. Over the whole incubation period, the effects of N fertilization on straw decomposition first increased and then decreased. The promotion degree of high and low N fertilization on straw decomposition was up to 15.8% and 7.9%, respectively. Over the whole incubation period, the inhibition degree of low N fertilization reached up to 7.1%, while high N fertilization showed a slight promotion trend of 0.7%. Therefore, the regulation of C:N by straw combined with fertilizer N not only affected the contribution of exogenous straw to SOC but also influenced the decomposition of endogenous SOC, and then influenced soil C fixation. Over the whole incubation period, straw C retention could not compensate for CO₂ released by the priming effects, which led to a net loss of SOC.

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