Organic compost application plays an important role in improving the fertility of Mollisol. However, the effects of different organic composts on carbon sequestration varies greatly and its internal mechanism are unclear. We conducted a field experiment to explore the residual proportion of different organic composts and their effects on carbon emissions in dryland Mollisol in Northeast China. There were a total of seven treatments, including chemical fertilizer control (SNF), organic composts from cattle excreta (CRH), sheep excreta (SHP), chicken excreta (CKN), residue after corn starch production (BCS), residue with crop straws (HRS) and mushroom residue (WMC). We monitored annual soil CO2 flux by static chamber method, as well as the changes of environmental factors and soil dissolved carbon and nitrogen. The regulatory mechanism of organic component characteristics on carbon residual porprotion of organic composts were examined by neural network analysis. The results showed that compared with the SNF treatment, soil dissolved organic carbon (DOC) and extractable organic nitrogen increased by 26.3%-103.5% and 21.4%-150.0%, respectively. The aromaticity of soil DOC was significantly reduced. Heterotrophic respiration flux was mainly affected by soil temperature and DOC content, while its temperature sensitivity was significantly reduced in the CKN treatment. Annual accumulation of heterotrophic respiration increased from 203 g·C·m-2 of the control to 234-334 g·C·m-2 under treatments with organic composts applications, with the CKN and HRS treatments showing the strongest impact. The annual carbon residual proportion of different organic composts in Mollisol was in an order of CRH (91.2%)> WMC (82.9%)> BCS (82.6%)> SHP (78.1%)> CKN (70.2%)> HRS (69.3%). Hemicellulose content and C/N of organic composts were the key factors, which explained 58.8% and 32.9% of the total variations of carbon residual proportion. Organic compost from cattle excreta had higher residual proportion due to lower C/N, hemicellulose content and soluble polyphenol content, and thus did not significantly affect Mollisol heterotrophic respiration. Therefore, the application of organic compost from cattle excreta was more efficient to improve organic carbon in dryland Mollisol.
施用有机肥对黑土肥力提升具有重要作用,但不同种类有机肥的固碳效果存在较大变异且内在机制尚不清楚。为探究不同有机肥的残留及其对土壤碳排放的影响,选取东北旱作黑土开展田间试验,设置仅施化肥对照(SNF)和施用牛粪(CRH)、羊粪(SHP)、鸡粪(CKN)、玉米淀粉渣(BCS)、秸秆(HRS)、菇渣(WMC)制成的有机肥,共7个处理。利用静态箱法监测全年土壤CO2排放通量,同步测定环境因子和土壤活性碳、氮含量,并运用神经网络分析揭示有机组分特征对有机肥碳残留率的调控机制。结果表明: 与SNF处理相比,有机肥处理使土壤溶解性有机碳(DOC)含量增加26.3%～103.5%,可浸提有机氮含量提高21.4%～150.0%,但是明显降低了土壤DOC的芳香度。土壤异养呼吸通量主要受土壤温度和DOC含量影响,且其温度敏感性在CKN处理显著降低。施用有机肥使土壤异养呼吸年累积量由对照的203 g·C·m-2增至234～334 g·C·m-2,其中CKN和HRS处理最显著。黑土中不同有机肥处理周年碳残留率为CRH(91.2%)>WMC(82.9%)>BCS(82.6%)>SHP(78.1%)>CKN(70.2%)>HRS(69.3%),有机肥半纤维素含量和碳氮比是影响其碳残留率的关键因素,解释度分别为58.8%和32.9%。低碳氮比与低半纤维素、溶解性多酚含量使牛粪有机肥具有最高的碳残留率且不显著影响黑土异养呼吸。综上所述,施用牛粪有机肥更有助于实现旱作黑土有机碳的高效提升。.
Keywords: CO2 emission; Mollisol; carbon residual proportion; organic component; organic compost.