作物残体与其生物炭配施对土壤有机碳及其自身矿化率的提升

【目的】本研究通过探讨小麦和玉米残体与其生物炭配施对土壤各组分有机碳及其自身有机碳矿化的影响,揭示其在土壤固碳和培肥方面的效应,为农田有机物资源合理利用提供理论支撑。【方法】采用室内恒温培养试验,共设置小麦或玉米残体(根茬、秸秆)和秸秆制成的生物炭单施(WS、WR、WB、MS、MR、MB),配施(WS+WB、WR+WB、MS+MB、MR+MB)以及对照(CK)构成的11个处理,培养期间测定土壤CO2释放量,培养结束后测定土壤总有机碳(TOC)、可溶性有机碳(DOC)、微生物量碳(MBC)、颗粒有机碳(POC)以及粗细颗粒有机碳含量(CPOC、FPOC)。【结果】添加玉米有机物料对土壤TOC、MBC、POC、CPOC和FPOC含量的增加作用普遍高于添加小麦有机物料。添加小麦或玉米秸秆对土壤TOC、POC、CPOC、FPOC含量的增加作用均高于添加根茬。单独添加生物炭,作物残体与生物炭配施和单独添加作物残体处理分别在培养的第4、8、21 d有机碳矿化速率最大,为有机碳矿化快速期,之后矿化速率减缓并逐渐趋于稳定。单独添加作物残体其有机碳累积矿化率最大,达到30%~46%;与对照相比,添加有机物料的各处理均显著增加了土壤TOC含量,其中添加生物炭处理土壤TOC含量增幅最大;单独添加小麦和玉米生物炭处理,土壤TOC含量分别显著增加34.4%和36.5%,但其有机碳累积矿化率仅为3%左右,土壤FPOC含量及敏感性指数在单独添加生物炭处理最高;小麦和玉米残体与其生物炭配施处理,土壤MBC和CPOC含量分别显著增加80.2%~199.2%,且其有机碳累积矿化率为12%~19%,介于生物炭和残体单施之间,土壤CPOC含量及敏感性指数均表现为配施处理最高。【结论】单独添加作物残体能够较好地补充土壤养分,但CO2释放量显著高于单施生物炭及配施处理;单独添加生物炭其有机碳累积矿化率较低,短期内对土壤养分的补充作用较小。作物残体与其生物炭配施可以较好地克服各自单独施用的弊端,尤其是玉米秸秆与其生物炭配施,在保证作物养分供应的同时能增加土壤碳库储量,对土壤肥力提升效果更好。

Combined addition of crop residues and their biocharincrease soil organic C content and mineralization rate

【Objectives】This study investigated effects of single or combined addition of crop residues and straw biochar on the contents of soil organic carbon components and their mineralization, and revealed their effects in terms of soil carbon sequestration and fertility improvement, therefore provided theoretical support for reasonable utilization of farmland organic resources.【Methods】 An incubation experiment was carried out for 83 days with totally 11 treatments, control soil (CK), single addition (WS, WR, WB, MS, MR and MB) and combined addition (WS+WB, WR+WB, MS+MB and MR+MB) of wheat or maize residues (root, straw) and straw biochar. The experiment measured soil CO2 emission during cultivation, at the end of the experiment, soil total organic carbon (TOC), dissolved organic carbon (DOC), microbial biomass carbon (MBC), particulate organic carbon (POC) and coarse, fine particulate organic carbon (CPOC and FPOC) were also determined.【Results】 The contents of soil TOC, MBC, POC, CPOC and FPOC under the adding maize residue are higher than those of adding wheat residue, and the addition of shoots increases the contents of soil TOC, POC, CPOC and FPOC more obviously compared to the addition of roots. The organic carbon mineralization rates are rapid at the beginning of 4, 8, 21 d under treatments of single addition biochar, combination of crop residues and biochar and single addition crop residues respectively, then slow down and gradually stabilize. The single addition of crop residues has the maximum cumulative mineralization rate of organic carbon (up to from 30% to 46%). Compared with the control, the treatments of adding organic materials all significantly increase the content of soil TOC, and the single addition of biochar has the largest increase (by 34.4% and 36.5% under the single addition of wheat or maize straw biochar respectively), but the cumulative mineralization rate of organic carbon is only 3%. The soil FPOC content and sensitivity index of the single addition biochar treatments are higher than those of the others. The treatments with mixed wheat or maize residue and their biochar significantly increase the contents of soil MBC and CPOC by 102.2%, 109.3% and 199.2%, 80.2% respectively and the cumulative mineralization rate of organic carbon is between 12% to 19%. The treatments of combining addition crop residues and biochar also have the highest soil CPOC contents and sensitivity indices.【Conclusions】 The complementary role of soil nutrients is obvious in adding crop residues alone treatments, while the CO2 released rates of the adding crop residues alone treatments are higher than those of the other treatments, and the single addition of biochar has the lowest cumulative mineralization rate, therefore, the supply of soil nutrients is limited. Over all, the combined addition of crop residues and their biochar can better overcome their drawbacks, especially for maize straw and its biochar mixture, which can both increase soil carbon reservoir and ensure the supply of soil nutrients, have significant effect on soil fertility enhancement.