Table_4_Effect of Tillage Treatment on the Diversity of Soil Arbuscular Mycorrhizal Fungal and Soil Aggregate-Associated Carbon Content.DOCX

No-tillage agriculture can sustain productivity and protect the environment. A comprehensive understanding of soil arbuscular mycorrhizal (AM) fungal diversity and soil carbon distribution within aggregate fractions is essential to the evaluation of no-tillage agriculture. The long-term field experiment included two tillage treatments (1) no tillage with straw returned to the soil (NTS), and (2) conventional mouldboard-plowing tillage without straw (CT), and was conducted on the Loess Plateau, north-western China, from October 2009. The soil samples were collected from the surface layer (0–20 cm depth) at the maturation stage of the summer maize (Zea mays L.) for analyzing aggregates separated by the dry-sieving method. The organic carbon content in the bulk soil and different particle size aggregates were measured using the dichromate oxidization method. The species compositions of soil AM fungi were compared by applying high-throughput sequencing of 18S rRNA. The results showed that the NTS had 9.1–12.2% higher percentage of soil macro-aggregates, resulting in 9.8% increase in mean weight diameter and 10.0% increase in bulk soil organic carbon content as compared with CT treatment. In addition, the NTS treatment had significantly higher percentages of Septoglomus and Glomus than the CT treatment. We also found some significant differences in the fungal communities of the soils of the two treatments. There was a strong positive relationship between bulk soil organic carbon and the percentages of Septoglomus and Glomus. Our results suggested that the NTS treatment had a protective effect on AM fungal community structures, which might play a key role in the development of agricultural sustainability in the Loess Plateau of China.

免耕农业能够维持生产力并保护环境。对土壤丛枝菌根（AM）真菌多样性和土壤碳在团聚体分数中的分布的全面理解，对于评估免耕农业至关重要。该长期田间试验包括了两种耕作处理：（1）将秸秆返还土壤的免耕（NTS），以及（2）无秸秆的传统犁耕（CT），该试验于2009年10月在中国西北部的黄土高原进行。在夏玉米（Zea mays L.）成熟期，从表层（0-20厘米深度）收集土壤样本，以分析通过干筛法分离的团聚体。采用重铬酸钾氧化法测量了大量土壤和不同粒径团聚体中的有机碳含量。通过18S rRNA的高通量测序比较了土壤AM真菌的物种组成。结果表明，与CT处理相比，NTS处理具有9.1-12.2%更高的土壤宏观团聚体百分比，导致平均重量直径增加了9.8%，大量土壤有机碳含量增加了10.0%。此外，NTS处理比CT处理具有显著更高的Septoglomus和Glomus百分比。我们还发现两种处理土壤的真菌群落存在一些显著差异。大量土壤有机碳与Septoglomus和Glomus的百分比之间存在强烈的正相关关系。我们的结果表明，NTS处理对AM真菌群落结构具有保护作用，这可能在促进中国黄土高原的农业可持续性发展中发挥关键作用。