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为研究水稻秸秆添加对砂姜黑土水稳性团聚体分布及稳定性的影响,探索水稻秸秆腐解过程中外源新碳及原有机碳在不同粒级团聚体中的分配规律,该文通过室内模拟试验,运用δ~(13)C示踪方法,将稳定同位素碳(δ~(13)C)标记的水稻秸秆添加入砂姜黑土,利用湿筛法得到不同培养时期不同粒级的土壤水稳性团聚体,测定不同时期各粒级土壤外源新碳及原有机碳含量。结果表明:未添加水稻秸秆的砂姜黑土(对照组),水稳性微团聚体(<250μm)占主体,团聚体有机碳含量低。与对照相比,添加水稻秸秆(试验组)显著促进了>2000、2000~250μm粒级水稳性大团聚体的团聚(P<0.05);培养到120 d时,>2000、2000~250μm水稳性团聚体比对照组分别增加了265.5%、16.0%,促使水稳性大团聚体(>250μm)占主体,显著提高了砂姜黑土水稳性团聚体的平均重量直径(mean weight diameter,MWD)、几何平均直径(geometric mean diameter,GMD)、水稳性大团聚体含量(R0.25),降低了分形维数(D)值(P<0.05),土壤结构稳定性明显得到改善。试验组各粒级团聚体有机碳含量显著增加,培养到15 d时,>2000、2000~250、>250~53、<53μm粒级团聚体有机碳分别比对照组增加了21.4%、25.4%、34.7%、50.0%,其中微团聚体有机碳增加幅度大于大团聚体的增加幅度。MWD、GMD、R0.25与2000~250、>250~53μm粒级团聚体有机碳呈极显著正相关关系(P<0.01),与>2000μm粒级团聚体有机碳呈显著正相关关系(P<0.05)、与<53μm粒级团聚体有机碳关系不显著。不同粒级团聚体的δ~(13)C值明显增加,动态变化较大,表明外源新碳周转速率较快。外源新碳主要分配在>250~53、<53μm粒级微团聚体中,分配比例分别为38%、28%,外源新碳的分解速率明显快于原有机碳。研究得出添加水稻秸秆有利于增加砂姜黑土的团聚体稳定性,提高土壤及不同粒级团聚体的有机碳含量,提升土壤碳水平,改善了土壤结构,这为淮北地区土壤质量提升及有机碳循环提供了理论依据。
In order to study the effects of rice straw addition on the distribution and stability of water-stable aggregates in Shajiang black soil, and to explore the rules of distribution of new carbon and organic carbon in different size aggregates during the decomposition of rice straw, Simulated experiments were conducted by using δ ~ (13) C tracer method. Stable isotope carbon (δ ~ (13) C) -targeted rice straw was added into Shajiang black soil, and different sizes of soil water Stable aggregates, the determination of different levels of soil in different levels of new carbon and organic carbon content. The results showed that the water-stable microaggregates (<250μm) accounted for the main part of Shajiang black soil without rice straw (control group), and the organic carbon content of the aggregates was low. Compared with the control, the addition of rice straw (experimental group) significantly promoted the agglomeration of water-stable macro-aggregates> 2000 and 2000-250 μm (P <0.05) The stable aggregates increased by 265.5% and 16.0% respectively compared with the control group, which led to the main body of water-stable macroaggregates (> 250μm), significantly increasing the average weight diameter of water-stable aggregates MWD, geometric mean diameter (GMD) and water-stable macroaggregates (R0.25) decreased the value of fractal dimension (D) (P <0.05), and the soil structure stability was obviously improved. Compared with the control group, the organic carbon content of grain aggregates> 2000, 2000 ~ 250,> 250 ~ 53 and <53μm increased by 21.4% and 25.4% , 34.7% and 50.0% respectively. The increase of organic carbon in microaggregates was larger than the increase of macroaggregates. There was a significant positive correlation between MWD, GMD, R0.25 and 2000 ~ 250 and> 250 ~ 53μm aggregates of organic carbon (P <0.01) and a significant positive correlation with organic carbon of> 2000μm aggregates <0.05), but not significant with the aggregates of <53μm aggregates. The δ ~ (13) C values of aggregates with different size fractions increased obviously and showed great dynamic changes, which indicated that the turnover rate of new exogenous carbon was faster. Exogenous new carbon is mainly distributed in> 250 ~ 53, <53μm particle size microaggregates, the distribution ratio was 38%, 28%, the decomposition of new exogenous carbon was significantly faster than the original organic carbon. The results showed that adding rice straw was beneficial to increase the stability of aggregates, increasing the organic carbon content of soil and different size aggregates, increasing the soil carbon and improving the soil structure, Carbon cycle provides a theoretical basis.