Straw return is a popular management strategy to improve soil organic carbon (SOC) and change soil microbial community structure in agro-ecosystems. In the North China plain, the average straw incorporation rate is 6000–10,000 kg ha⁻¹, however, effective utilization of maize straw is difficult because of its large amount and volume. A four-year (2014–2017) experiment was conducted to investigate the effects of different forms of maize straw on subsoil SOC fractions and microbial communities under deep-buried (30–40 cm) management in a typic Agrosol in Liaohe plain. Six treatments were established: no straw (CK, 0 kg ha⁻¹), whole straw (WS, 6000 kg ha⁻¹), chopped straw (CS, 6000 kg ha⁻¹), pelletized straw (PS, 6000 kg ha⁻¹), straw biochar (BC, 2010 kg ha⁻¹) and straw ash (SA, 960 kg ha⁻¹). Soil organic carbon, dissolved organic carbon (DOC), microbial biomass carbon (MBC), and bacterial and fungal diversity and abundance were analysed by chemical and molecular methods. Compared with CK, the five treatments significantly increased the SOC pool by 1.4–4.8 % in the 0–20 cm soil depth and 3.2–14.2 % in the 20–40 cm depth, with the highest increase under CS. Both CS and WS significantly increased the DOC and MBC, with higher DOC/SOC and MBC/SOC ratios. Notably, straw incorporation showed greater effects on DOC and MBC and a higher increase in SOC fractions in the 20–40 cm depth. Principal component analysis and similarity analysis showed that the different forms of straw incorporation caused significant variations in microbial community structure in the subsoil layer. The BC and SA significantly increased the diversity of soil microorganisms, while CS and WS altered the relative abundance of the dominant bacterial phyla Acidobacteria, Nitrospirae, Proteobacteria, Verrucomicrobia and dominant fungal phyla Ascomycota, Morttierellomycota, Glomeromycota, which increased with increases in SOC fractions. Our results showed that regulation of C-related microbial abundance in the subsoil was more conducive to improving SOC fractions than simply improving soil microbial diversity. Since chopped straw significantly increased the abundance of C-related microflora and SOC fractions, it should be the optimal form of incorporation in deep-buried straw management.

秸秆还田是改善农业生态系统中土壤有机碳（SOC）并改变土壤微生物群落结构的流行管理策略。在华北平原，秸秆的平均掺入量为6000–10,000 kg ha ^-1，但是，由于秸秆的数量大，体积大，难以有效利用。进行了一个为期四年（2014-2017年）的实验，研究了在辽河平原典型农用土壤中深埋（30-40 cm）管理下，不同形式的玉米秸秆对土壤SOC和微生物群落的影响。建立了六种处理方法：无秸秆（CK，0 kg ha ^-1），全秸秆（WS，6000 kg ha ^-1），切碎的秸秆（CS，6000 kg ha ^-1），粒状秸秆（PS，6000 kg ha）^-1），秸秆生物炭（BC，2010 kg ha ^-1）和秸秆灰烬（SA，960 kg ha ^-1）。通过化学和分子方法分析了土壤有机碳，溶解有机碳（DOC），微生物生物量碳（MBC）以及细菌和真菌的多样性和丰度。与CK相比，这5种处理在0–20 cm土层中使SOC池显着增加1.4–4.8％，在20–40 cm土层中使SOC池增加3.2–14.2％，在CS下增幅最大。CS和WS都显着增加了DOC和MBC，同时具有更高的DOC / SOC和MBC / SOC比。值得注意的是，秸秆掺入对DOC和MBC的影响更大，而在20–40 cm的深度中SOC分数的增加则更大。主成分分析和相似性分析表明，秸秆掺入的不同形式引起了下层土壤微生物群落结构的显着变化。酸杆菌门，硝化螺旋菌门，变形菌，疣微菌门和主导真菌门类子囊菌，Morttierellomycota，球囊菌门，其与在SOC馏分增加而增加。我们的结果表明，与简单改善土壤微生物多样性相比，调节土壤中C相关微生物的丰度更有助于提高SOC含量。由于切碎的秸秆会显着增加C相关微生物区系和SOC组分的含量，因此它应该是深埋秸秆管理中掺入的最佳形式。