• ISSN 1008-505X
  • CN 11-3996/S

长期秸秆还田下水稻土铁氧化物形态对团聚体稳定性的贡献

Contribution of iron oxides to aggregate stability in long-term straw returned paddy soil

    摘要
  • 摘要:
    目的 铁氧化物是土壤团聚体形成和稳定过程中重要的无机胶结剂。研究长期秸秆还田下土壤团聚体中铁氧化物形态及分布的变化，以进一步阐明长期秸秆还田改善土壤结构的机理。
    方法 基于湖南祁阳红壤实验站2012年开始进行的双季稻长期定位试验，采集连续11年秸秆不还田(NPK)、仅早稻秸秆还田(NPKRS1)及早稻秸秆和晚稻秸秆均还田(NPKRS2)处理的原状土，通过干湿筛法分离土壤团聚体(粒径>2、0.25～2、0.053～0.25和<0.053 mm)，测定了团聚体中络合铁(FePP)、非晶形铁氧化物(FeHH)和晶形铁氧化物(FeDH)含量，并分析了团聚体中3种铁氧化物与团聚体稳定性的关系。
    结果 与NPK处理相比，NPKRS1和NPKRS2处理均显著提高了>2 mm团聚体质量百分含量，降低了0.25～2 mm的团聚体质量百分含量，团聚体平均重量直径(MWD)分别显著提高了41.8%和57.2%，几何平均直径(GMD)分别显著提高了32.8%和36.3% (P<0.05)。长期秸秆还田后，所有铁氧化物含量在0.053～0.25 mm团聚体中均显著提高；FeHH含量在<0.053 mm粒级团聚体中没有显著变化，在其他粒级团聚体中显著增加了13.9%～56.0%。>0.053 mm团聚体中FeHH含量和0.053～0.25 mm团聚体中FePP、FeDH含量均与团聚体MWD呈显著正相关(P<0.05)，<0.053 mm团聚体中FePP含量和0.25～2 mm团聚体中FeDH含量均与团聚体MWD呈显著负相关。>2 mm团聚体中FeHH、0.25～2 mm团聚体中FeDH、0.053～0.25 mm团聚体中FePP、0.25～2 mm团聚体中FeHH、0.053～0.25 mm团聚体中FeDH、<0.053 mm团聚体中FePP对团聚体稳定性的影响最大，分别解释了团聚体MWD变异的5.8%、5.7%、5.7%、5.4%、5.3%、4.5%。
    结论 长期秸秆还田促进络合铁和晶形铁氧化物在0.053～0.25 mm团聚体中的富集，促进非晶形铁氧化物在>0.053 mm团聚体中的富集，有利于>2 mm团聚体的形成，从而提高土壤团聚体的稳定性。

     

    Abstract:
    Objectives Iron oxides are important inorganic aggregating agents for the formation and stability of soil aggregates. We studied the change of iron oxide content in soil aggregates under long-term straw returning, to explain the beneficial roles of straw returning in improving soil textures.
    Methods A field experiment of double-cropping rice was conducted in Qiyang, Hunan Province since 2012. In 2023, soil samples were collected from the plots of NPK (no straw returning), NPKRS1 (early rice straw returning), and NPKRS2 (both early and late rice straw returning) treatments for the analysis of the contents of >2 mm, 0.25−2 mm, 0.053−0.25 mm, and <0.053 mm aggregates, and the contents of iron oxides, including complex iron (Fepp), amorphous iron oxides (FeHH), and crystalline iron oxides (FeDH) in soil aggregates, and the relationship between soil aggregates stability and the three kinds of iron oxides was discussed.
    Results Compared with the NPK, NPKRS1 and NPKRS2 treatments significantly increased the proportion of >2 mm aggregates and decreased the proportion of 0.25−2 mm aggregates, enhanced the mean weight diameter (MWD) of soil aggregates by 41.8% and 57.2%, and the geometric mean diameter (GMD) by 32.8% and 36.3%, respectively (P<0.05). After long-term straw returning, the contents of FeHH were not significantly changed in silt and clay particles, but significantly increased by 13.9%−56.0% in other particles, and the contents of all iron oxides in 0.053−0.25 mm aggregates were significantly increased. FeHH content in >0.053 mm aggregates and the FePP and FeDH contents in 0.053−0.25 mm aggregates were significantly positively correlated with MWD (P<0.05), while the FePP content in <0.053 mm aggregates and FeDH content in 0.25−2 mm aggregate were negatively correlated with aggregate MWD. The effects of FeHH in >2 mm, FeDH in 0.25−2 mm, FePP in 0.053−0.25 mm, FeHH in 0.25−2 mm, FeDH in 0.053−0.25 mm and FePP in <0.053 mm on the stability of aggregates were the highest, explaining 5.8%, 5.7%, 5.7%, 5.4%, 5.3%, and 4.5% of the variability in aggregate MWD, respectively.
    Conclusions Long-term straw returning may promote the enrichment of FePP and FeDH in 0.053−0.25 mm aggregates and FeHH in >0.053 mm aggregates, which is conducive to the formation of >2 mm aggregates and improve the stability of soil aggregates.

     

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