摘要:土壤有机碳和团聚体对土壤肥力、作物产量、农业和环境发挥着重要作用，是土壤肥力的核心和可持续农业的基础。本研究依托中国科学院栾城农业生态系统试验站18年野外长期有机质物料和矿质肥料配施试验，开展不同施肥模式对土壤团聚体组成以及各组分有机碳在团聚体中分布影响的研究，为阐明不同农业管理措施下土壤有机碳的物理保护机制提供依据。试验共设6个处理：对照（CK）、单施秸秆（S）、单施有机粪肥（M）、单施化肥（NPK）、化肥配施秸秆（SNPK）和化肥配施有机粪肥（MNPK）。利用干筛法将全土筛分为大团聚体（> 2 mm）、小团聚体（0.25~2 mm）和微团聚体（< 0.25 mm）3种粒径团聚体，分别测定不同处理下全土及3种粒级团聚体中总有机碳（TOC）、可溶性有机碳（DOC）、酸解活性有机碳（AC）、惰性有机碳（ROC）和易氧化有机碳（LOC）含量。结果表明：施肥对土壤团聚体分布及稳定性有显著影响，SNPK显著提高了粒径> 0.25 mm团聚体含量和团聚体稳定性；DOC和ROC含量与粒径> 2 mm团聚体含量显著正相关，其对促进大团聚体形成至关重要。不同施肥处理下土壤团聚体各有机碳组分含量存在差异，与传统的单独施用化肥处理（NPK）相比，SNPK和MNPK均显著提高了全土和团聚体各组分有机碳含量，SNPK对土壤有机碳的提升效果优于MNPK。各有机碳组分在团聚体中的含量均为小团聚体>大团聚体>微团聚体，其中，70%以上的各组分有机碳来自于粒径> 0.25 mm的团聚体。在施用化肥基础上增施有机肥（MNPK）和实施秸秆还田（SNPK）提高了LOC在TOC中的占比，使LOC/TOC由CK的11.94%分别增加到14.95%和15.70%。MNPK利于LOC保存在大团聚体中，提高了土壤供肥能力；而SNPK促进了LOC向较小粒径团聚体迁移，增强了其在团聚体中的稳定性，提高了土壤的保肥能力。由此可见，长期实施有机无机肥料配合可以提高土壤碳储量和稳定性，这为全面实施秸秆还田的基础上推行有机粪肥部分替代化肥的养分管理策略提供了理论依据。
关键词:长期施肥/
土壤团聚体/
有机碳组分/
化肥/
秸秆/
有机粪肥
Abstract:Soil organic carbon and aggregates play an important role in soil fertility, crop yield, and the farmland environment, all of which are key components for sustainable agriculture. A wild long-term organic material and mineral fertilizer field experiment was initiated in 2003 at the Luancheng Agroecosystem Experimental Station of the Chinese Academy of Sciences. The experiment sought to investigate how different fertilization patterns affect the soil aggregate composition and the levels of organic carbon in the aggregates to better understand how different agricultural management practices serve as physical protection mechanisms. There were six treatments: no fertilization (i.e., conventional, CK), straw application alone (S), organic manure application alone (M), mineral fertilizer application (NPK), NPK plus straw (SNPK), and NPK plus organic manure (MNPK). The contents of total organic carbon (TOC), soluble organic carbon (DOC), acidolytic active organic carbon (AC), resistant organic carbon (ROC), and labile organic carbon (LOC) were examined within the aggregate fractions, including the total soil, large aggregates (>2 mm), small aggregates (0.25-2 mm), and microaggregates (< 0.25 mm). The results showed that fertilization had a significant effect on the distribution and stability of soil aggregates. SNPK significantly increased the amount of >0.25 mm aggregates. The contents of DOC and ROC were positively correlated with the amount of large aggregates and promoted the formation of large aggregates. Compared with NPK, SNPK and MNPK significantly increased the contents of SOC components in the aggregate fractions, and SNPK addition improved the SOC content compared to MNPK. In the aggregate fractions, the content of each organic carbon component was in the order of small aggregates > large aggregates > microaggregates, and more than 70% of the organic carbon came from the >0.25 mm aggregates. The LOC/TOC ratio in the MNPK and SNPK treatments increased to 14.95% and 15.70%, respectively, which was 11.94% under CK treatment. MNPK was conducive to LOC storage in large aggregates, which improved the soil fertilizer supply capacity; while SNPK promoted LOC migration to the small-sized aggregates, enhanced its stability in the aggregates, and improved the soil fertilizer retention capacity. In conclusion, long-term organic and inorganic fertilizer combined application improved soil carbon storage and stability. The study provides a theoretical basis for a nutrient management strategy with partial substitution of chemical fertilizer by organic manure and straw.
Key words:Long-term fertilization/
Soil aggregates/
Organic carbon fractions/
Chemical fertilizers/
Straw/
Organic manure
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