Organic amendments and nitrogen fertilization are common practices in agriculture, which have complex influences on the carbon cycle. To evaluate the effects of nitrogen-organic carbon combination on CO₂ efflux, we conducted a field incubation experiment with control, N fertilization without and with straw/biochar amendments for 20 months in a typical soil of North China Plain. CO₂ efflux was measured every ~3–4 weeks, and water-extractable organic carbon and soil microbial biomass carbon were analyzed in spring, summer, and autumn. Our results showed an asymmetric seasonality (slow increase in spring but rapid decrease in fall) in the control and biochar treatments, but a symmetric seasonality under straw treatments. Organic amendments with N fertilization caused an increase of CO₂ efflux in most seasons (comparing without N fertilization), with a much greater increase in spring–summer of the first year (22%–35%) than the second year (1%–3%). Nitrogen fertilization caused a much greater increase in cumulative CO₂ efflux with biochar (7%–13%) and with straw treatment (20%) than without organic amendments (3%) over the period of 20 months. SIC content showed an increase under organic amendments, with a greater increase under biochar amendments than straw amendments. The increases of CO₂ efflux under nitrogen-biochar and nitrogen-straw combinations could be explained mainly by enhanced decomposition of SOC, biochar, and straw rather than SIC dissolution. Our study indicated that biochar amendments were more effective for carbon sequestration than straw amendments and nitrogen fertilization with organic amendments could cause changes in various processes of CO₂ production in the cropland of north China.

中文翻译：

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氮肥施用对高 pH 值土壤中 CO2 外排的影响（有和没有有机改良剂）


有机改良剂和氮肥施肥是农业中的常见做法，它们对碳循环有复杂的影响。为评价氮-有机碳组合对 CO₂ 外排的影响，我们在华北平原典型土壤中进行了为期 20 个月的田间培养试验，包括对照、无氮肥和有秸秆/生物炭改良剂。每 ~3-4 周测量一次 CO₂ 外排量，并在春季、夏季和秋季分析可水溶性有机碳和土壤微生物量碳。我们的结果表明，对照和生物炭处理的季节性不对称（春季缓慢增加，秋季迅速减少），但在秸秆处理下呈对称季节性。施用氮肥的有机改良剂在大多数季节导致 CO₂ 外排增加（与不施氮相比），第一年春夏 （22%–35%） 的增加幅度远大于第二年 （1%–3%）。在 20 个月的时间内，施氮肥导致生物炭 （7%-13%） 和秸秆处理 （20%） 的累积 CO₂ 外排增加比没有有机改良剂 （3%） 大得多。有机改良剂下 SIC 含量增加，生物炭改良剂下比秸秆改良剂增加更多。氮-生物炭和氮-秸秆组合下 CO₂ 外排的增加主要可以解释为 SOC、生物炭和秸秆分解增强，而不是 SIC 溶解。我们的研究表明，生物炭改良剂比秸秆改良剂对碳封存更有效，有机改良剂施氮肥会导致华北农田_CO2 生产的各个过程发生变化。