生物质炭对稻田土壤团聚体稳定性和微生物群落的影响

土壤团聚体决定着土壤功能与质量，受土壤生物与非生物因素的共同作用。本文从非生物和生物学角度解析生物质炭施用对土壤团聚体稳定性的长期影响。以句容和南京两个独立施用生物质炭3年或5年后的稻田麦季土壤为研究对象，选取常规施肥（CK）和常规施肥+生物质炭（AB）处理，利用湿筛法获得不同粒级土壤团聚体，并测定其中有机碳（SOC）、全氮、全磷含量，同时采用定量PCR技术测定土壤微生物（细菌、真菌、丛枝菌根真菌、古细菌和放线菌）丰度。结果表明：句容和南京土壤AB处理生物质炭原位老化后，大团聚体比例（R>0.25）和土壤田间持水量显著增加，平均重量直径和几何平均直径表现出增加趋势（P>0.05）；土壤团聚体养分含量（SOC、全磷）和土壤微生物丰度发生显著变化。与对照处理相比，句容和南京老化生物质炭处理的土壤大团聚体比例分别显著增加93.0%和61.5%，0.002～0.053 mm和<0.002 mm粒级团聚体均呈减少趋势；句容和南京土壤AB处理全土SOC含量分别显著增加26.3%和26.9%，大团聚体中SOC含量分别显著增加72.4%和52.3%，微团聚体中SOC含量分别显著增加20.8%和30.0%，全土真菌丰度显著增加；南京土壤全磷含量显著增加25.4%，丛枝菌根真菌和古细菌丰度也呈增加趋势（P>0.05）。由相关性分析可知，土壤团聚体平均重量直径与大团聚体比例、SOC含量、真菌和丛枝菌根真菌丰度极显著正相关（P<0.01），与全磷含量和古细菌丰度显著正相关，相关系数分别为0.641和0.646。综上所述：生物质炭可以改善土壤pH值，田间持水量等理化性质，增加稻-麦轮作麦季土壤0.25～2 mm大团聚体比例和碳、磷含量，增加土壤真菌、丛枝菌根真菌和古细菌丰度，提高土壤团聚体稳定性，具有持续性。

Effects of Biochar on Soil Aggregate Stability and Microbial Community in Paddy Field

[Objective] Soil aggregates, subjected to the joint impact of soil biological and non-biological factors, play a crucial role in determining soil functions and ecosystem services. Soil microorganisms are one of the most active biological factors that affect the formation of soil aggregates. This study is aimed to explore long-term effects of biochar application on stability of paddy soil aggregates in paddy soil at two locations from abiotic and biological perspectives.[Method] From two long-term field experiments under the wheat-rice rotation system, located in Jurong and Nanjing, separately, 3 and 5 years old in history, and consisting of two treatments each, i.e. CK (Conventional fertilization) and AB (Conventional fertilization + biochar), soil samples were collected after harvesting wheat in the annual rice-wheat rotations for particle size fractionation of soil aggregates using the wet sieve method, and for analysis of contents of organic carbon, total nitrogen and total phosphorus as well as abundance of soil microorganisms (bacteria, fungi, arbuscular mycorrhizal fungi, archaea and actinobacteria) in each fraction of soil aggregates using the quantitative PCR technique.[Result] Treatments AB in the two field experiments were significantly higher in macro aggregate ratio (R_>0.25) and field soil water holding capacity after biochar getting aged in situ, and exhibited increase trends in both mean weight diameter and geometric mean diameter (P>0.05). Soil nutrient contents (SOC, total phosphorus) and soil microbial abundance in soil aggregates changed significantly, too. Compared with Treatment CK, Treatment AB was 93.0% and 61.5% higher in content of macro aggregates, respectively, in the Jurong and Nanjing experiments, but exhibited a decreasing trend in both the 0.002-0.053 mm and <0.002 mm fractions of soil aggregates; besides, Treatment AB was significantly or 26.3% and 26.9% higher in SOC content of the bulk soil, 72.4% and 52.3% higher in SOC content of the macro aggregates, and 20.8% and 30.0% higher in SOC content of the micro aggregates, respectively, in the Jurong and Nanjing experiments, significantly higher in fungi abundance of the bulk soil in both experiments, significantly or 25.4% higher in total phosphorus in the Nanjing experiment; and also exhibited an increasing trend in abundance of the arbuscular mycorrhizal fungi and archaea(P>0.05). Correlation analysis showed that the soil aggregate mean weight diameter was very significantly and positively related to macro aggregate ratio, SOC content, abundance of fungi and arbuscular mycorrhizal fungi(P<0.01). The total phosphorus content and archaea abundance were significantly and positively correlated, with correlation coefficient being 0.641 and 0.646, respectively.[Conclusion] Aging biochar improves soil pH, field water holding capacity, other physical and chemical properties, increases the proportion of 0.25-2 mm macro aggregates, SOC and total phosphorus content, and stabilizes soil aggregates. Moreover, it increases abundance of the soil microbes in the rice fields in Jurong and Nanjing to a varying degree. Aging biochar is beneficial to the growth of soil microorganisms, increases the abundance of fungi and arbuscular mycorrhizal fungi, promotes the formation of soil aggregates, and indirectly improves the stability of soil aggregates. To sum up, biochar demonstrates sustained effects of increasing macro aggregate ratio, carbon and phosphorus contents, and fungal, arbuscular mycorrhizal fungal and archaeal abundances, and improving soil aggregate stability during the wheat season of the rice-wheat rotation system.