1.Sichuan Agricultural University;2.Agricultural and Rural Bureau of Zhongjiang County
the National Key R&D Program of China (No. 2017YFD0301701), the Key R&D Program of Sichuan (No. 2021YFN0127).
【目的】土壤团聚体有机碳和胞外酶对于改善土壤结构和提高土壤碳固存能力至关重要，且受农艺生产措施显著影响。为探讨秸秆还田下有机碳组分及胞外酶活性变化，开展了35年水稻-小麦轮作定位试验。【方法】本试验设置了无肥区(CK)、化肥区(NPK)和秸秆还田+化肥区(NPKS)，研究了不同处理对土壤团聚体有机碳(SOC)及其活性组分[可溶性有机碳(DOC)、易氧化有机碳(EOC)、微生物生物量碳(MBC)]含量与碳循环相关胞外酶[β-1,4-葡萄糖苷酶(BG)、β-1,4-木糖苷酶(BX)、β-D-纤维二糖水解酶(CBH)]活性的影响。【结果】大于0.25 mm团聚体中SOC、DOC和MBC含量显著高于小于0.25 mm粒级，且均以NPKS处理的效果最优，促进了土壤大团聚体有机碳组分更新。各粒级团聚体中MBC/SOC和DOC/SOC比值相对稳定，这表明MBC和DOC与SOC的动态变化趋势较为一致，可作为评价土壤有机碳的敏感指标。2~0.25 mm粒级是团聚体胞外酶主要载体，均以NPKS处理活性最高；但大于2 mm团聚体酶活性在不同农艺措施之间差异不显著。土壤团聚体中有机碳组分与胞外酶表现为互相促进的关系，其中SOC、DOC和MBC分配差异的主要影响因子为CBH，次要影响因子是BG；而EOC仅受到CBH的正向影响。CBH和BG可促进土壤有机碳周转，且在2~0.25 mm大团聚体中互促作用更剧烈。【结论】长期秸秆还田配施化肥不仅有利于提升大团聚体碳的更新和周转速率，还提高了SOC含量，是稻田土壤可持续固碳的重要农艺途径。
【Objective】Soil aggregate organic carbon and extracellular enzymes play an important role in improving soil structure and carbon sequestration, which are easily affected by agronomic management practices. In order to study the effects of long-term straw returning combined with chemical fertilization on organic carbon components and extracellular enzymes in soil aggregates, a 35-year field positioning experiment was carried out. 【Method】The field experiment was designed to have three treatments in a rice-wheat rotation system: no chemical fertilizer (CK), chemical fertilizer only (NPK), and straw plus chemical fertilizer (NPKS). The contents of soil organic carbon (SOC) and its labile components [dissolved organic carbon (DOC), easily oxidizable organic carbon (EOC) and microbial biomass carbon (MBC)] in soil aggregate were analyzed, as well as the activities of extracellular enzymes related to carbon cycle [β-1,4-Glucosidase (BG), β-1,4-Xylosidase (BX) and β-D-Cellobiohydrolase (CBH)]. 【Result】The contents of SOC, DOC and MBC in >0.25 mm aggregates were significantly higher than those in <0.25 mm aggregates, and their contents of NPKS treatment were the highest. This showed that NPKS promoted soil macro-aggregates organic carbon regeneration. The values of MBC/SOC and DOC/SOC in each particle size aggregate were relatively stable, which indicated that dynamic change trends of MBC and DOC were consistent with that of SOC. Thus, MBC and DOC could be used as sensitive indexes to evaluate soil organic carbon. The 2-0.25 mm aggregates were the main carriers of extracellular enzymes, and their activities in NPKS treatment were the highest. However, the enzymes activities in >2 mm aggregates had no significant difference among treatments. The soil organic carbon components and extracellular enzymes in soil aggregates promoted each other, in which the contents of SOC, DOC and MBC in aggregates were mainly affected by CBH, followed by BG; while EOC was only positively affected by CBH. These two extracellular enzymes (CBH and BG) could promote soil organic carbon turnover and the interaction was enhanced in 2-0.25 mm aggregate. 【Conclusion】Long-term application of straw returning combined with chemical fertilizer could increase organic carbon regeneration and turnover rate, and increase soil organic carbon content, which is an important agronomic way for sustainable carbon sequestration in paddy soil.
Lixinyue, LiBing, Wangchangquan, Xieningyi, Motaixiang, Wangnanxi, Zhangqingwei. Effects of Long-term Straw Returning on Organic Carbon and Extracellular Enzymes in Paddy Soil Aggregates[J]. Acta Pedologica Sinica,,[In Press]