生物质炭和秸秆长期还田对红壤团聚体和有机碳的影响

要 ：秸秆还田和施用生物炭是提高土壤有机碳含量和改良土壤团聚体结构的有效方法,但长期施用生物炭与秸秆还田改良土壤的效率研究仍然缺乏比较。本研究针对中亚热带典型的旱地红壤,基于等碳量不同碳源投入的5年野外定位试验,研究秸秆还田、秸秆-猪粪配施和生物炭还田对红壤团聚体组成、稳定性和有机碳分布的影响,为建立红壤地力快速提升的有机培肥措施提供科学依据。本试验共设置对照、单施化肥、秸秆还田、秸秆-猪粪配施和生物炭还田五个处理,采用干筛和湿筛法分析了连续施用不同碳源5年后对土壤团聚体组成、稳定性和有机碳分布的影响。研究表明,施用等碳量的不同有机碳源5年后显著增加了土壤有机碳含量,其增幅顺序为：生物炭还田>秸秆-猪粪配施>秸秆还田。干筛法分析结果表明：与单施化肥处理相比,秸秆-猪粪配施和生物炭还田处理显著增加>0.25 mm机械稳定性团聚体含量(R_0.25)、平均重量直径(mean weight diameter, MWD)和几何平均直径(geometric mean diameter, GMD)；秸秆还田和生物炭还田处理显著增加了0.25-2 mm团聚体对土壤有机碳的贡献率。湿筛法分析结果表明：与单施化肥处理相比,秸秆还田和秸秆-猪粪配施处理显著增加R_0.25、MWD和GMD,但生物炭还田处理和单施化肥处理相比差异不显著；秸秆还田和秸秆-猪粪配施处理显著降低团聚体破坏率(PAD),生物炭还田处理显著增加了PAD；秸秆配施猪粪处理和秸秆还田处理显著增加了>2mm团聚体对土壤有机碳的贡献率。总体上,秸秆配施猪粪协同提高团聚体有机质含量和团聚体稳定性的作用比秸秆还田和生物炭还田要强。

Effects of Long-term Application of Biochar and Straws on Red Soil Aggregate Compostion and Organic Carbon Distribution

The applications of straw and biochar are effective methods to improve soil organic carbon and soil aggregate structure. However, their effectiveness to improve soil quality is not clear at the long term scale. In this study, a 5-year field experiment was conducted to study the impact of organic manure and biochar with equal amount of carbon input on soil aggregate composition, stability and organic carbon contents in an upland red soil in Middle subtropical region. The study included five treatments: blank treatment (CK), fertilizer (N), straw (NS), the mixed application of pig manure and straw (NSM) and the biochar (NB). The soil aggregate size fraction was examined by dry and wet sieving methods, respectively. The results showed that soil organic carbon content increased significantly after 5-year application of different types of organic carbon sources, and the order was as follows: NB> NSM> NS. For dry sieving, the results revealed that macro-aggregate content (R_0.25), mean weight diameter (MWD) and geometric mean diameter (GMD) were significantly higher under NSM and NB treatments than the N treatment. In general, the contributing rates of macro-aggregates to SOC in 0.25-2 mm fraction increased under NS and NB treatments. For wet sieving, the results revealed that R_0.25, mean weight diameter MWD and GMD were significantly higher under NSM and NS treatments than the N treatment. The percentage of aggregate destruction (PAD) significantly reduced under NS and NSM treatments, but increased under NB treatment. The contributing rates of macro-aggregates to SOC in >2 mm fraction increased under NSM and NS treatments. In general, the mixed application of pig manure and straw had a stronger capacity to improve synergically soil aggregate stability and organic carbon content in comparison with the straw or biochar returning.