覆膜栽培与施肥对秸秆碳氮在土壤团聚体中固持特征的影响

  目的  土壤中秸秆碳氮的分解与固定受栽培方式（包括覆膜）和施肥的影响。关于不同覆膜与施肥下秸秆碳氮在团聚体中固持特征仍不很明确。  方法  将表层土壤（0 ~ 20 cm）与13C15N双标记秸秆混合后在田间进行原位培养150 d，分析土壤团聚体有机碳中秸秆来源碳（13C-SOC）和氮中秸秆来源氮（15N-TN）的含量。  结果  施肥、栽培方式及二者交互作用显著影响（P < 0.05）> 0.25 mm团聚体中有机碳含量和 < 0.053 mm团聚体中有机碳和氮含量。不覆膜栽培下，与有机肥配施氮肥（M₂N₂）处理和不施肥（CK）处理相比，单施氮肥（N₄）处理使 > 0.25 mm团聚体中13C-SOC含量分别增加了36.36%和20.69%。覆膜栽培下，N₄与其他处理（M₂N₂和CK）相比，各级团聚体中13C-SOC含量增加了22.87% ~ 53.37%。不覆膜CK与覆膜CK处理相比，0.25 ~ 0.053 mm和 < 0.053 mm团聚体中13C-SOC含量增加了16.00%和46.15%（P < 0.05）。不覆膜栽培下，CK和M₂N₂处理与N₄处理相比，< 0.053 mm团聚体15N-TN含量分别增加了44.85%和28.60%。同一施肥处理，不覆膜栽培下秸秆来源碳氮对 < 0.053 mm团聚体中有机碳和氮的贡献率平均分别比覆膜栽培增加了55.06%和21.35%。秸秆碳氮在团聚体中的分配比例随团聚体粒径的增加而增加，其中秸秆碳和氮分配到 > 0.25 mm团聚体比例平均分别为22.22%和42.14%。  结论  土壤添加秸秆后秸秆碳氮主要固定于 > 0.25 mm团聚体，且单施氮肥促进了秸秆碳在各级团聚体中固存，不覆膜有利于 < 0.053 mm团聚体中碳氮的更新。

Effects of Plastic Film Mulching and Fertilization on Sequestration Characteristics of Straw-derived Carbon and Nitrogen in Soil Aggregates

  Objective  The decomposition and fixation of straw-derived carbon (C) and nitrogen (N) in soil were affected by cultivation measures including (plastic film mulching, PFM) and fertilization. However, the distribution and fixation characteristics of straw-derived C and N in aggregates under PFM and fertilization are still unclear.   Methods  The topsoil (0-20 cm) was mixed with 13C15N double-labeled straw and in situ incubation was carried out in the field for 150 days. The contents of straw-derived C (13C-SOC) and N (15N-TN) in soil aggregates were analyzed.  Results  Fertilizer application, cultivation measures and their interaction significantly affected organic C content in > 0.25 mm aggregates and organic C and N contents in < 0.053 mm aggregates (P < 0.05). Under the cultivation without PFM, N fertilizer treatment (N₄) had increased the 13C-SOC content in > 0.25 mm aggregate by 36.36% and 20.69% compared with the treatment of manure combined with N fertilizer (M₂N₂) and no fertilizer (CK). Under the cultivation with PFM, compared with other treatments (M₂N₂ and CK), the content of 13C-SOC in N₄ aggregates increased by 22.87%-53.37%. Compared with CK without PFM, the contents of 13C-SOC in 0.25 - 0.053 mm and < 0.053 mm aggregate were significantly increased (P < 0.05) by 16.00% and 46.15%. Under the cultivation without PFM, CK and M₂N₂ compared with N₄, the content of 15N-TN in 0.25-0.053 mm aggregate increased by 44.85% and 28.60%, respectively. Under the same fertilization treatment, the contribution percentage of straw-derived C and N to organic C and N of < 0.053 mm aggregates in no-PFM were 55.06% and 21.35% higher than those in PFM cultivation, respectively. The distribution percentage of straw-derived C and N in aggregate increased with the increase of aggregate sizes, and the proportions of straw-derived C and N in aggregates > 0.25 mm were 22.22% and 42.14%, respectively.  Conclusion  After adding straw to soil, straw-derived C and N were mainly fixed in > 0.25 mm aggregate and N fertilizer application alone promoted the C retention of straw in aggregates, the C and N regeneration in < 0.053 mm aggregate was facilitated in no-PFM cultivation.