秸秆与秸秆生物炭还田对石灰性潮土有机碳固定的影响

刘欣萌; 姜涵; 魏文良; 刘树堂

doi:10.19336/j.cnki.trtb.2022090701

秸秆与秸秆生物炭还田对石灰性潮土有机碳固定的影响

Effects of Straw and Straw Biochar Returning on Soil Organic Carbon Sequestration in Calcareous Fluvo-Aquic Soil

摘要

摘要:
目的为探明有机物料还田配合优化施氮对石灰性潮土土壤有机碳（SOC）及其活性组分、土壤团聚体的形成与稳定性的影响。
方法依托长期定位试验，设置农民习惯施氮（CF_N）、优化施氮（OF_N）、秸秆还田 + 优化施氮（S_N）和生物炭 + 优化施氮（BC_N）四个处理开展土壤有机碳固定效果与机制的研究。
结果四种施肥方式下，BC_N处理对土壤有机碳的提升效果最明显，达到18.68 g kg⁻¹，其次依次为S_N、CF_N和OF_N处理。与CF_N处理相比，有机物料还田配合优化施氮能够显著增加土壤微生物量碳（MBC）、可溶性有机碳（DOC）、颗粒态有机碳（POC）和易氧化有机碳（EOC）的含量，增幅分别为128.26%、96.62%、219.72%和45.42%；同时，> 0.25 mm团聚体的比例与土壤团聚体平均重量直径（MWD）显著提高，S_N与BC_N较CF_N处理> 0.25 mm团聚体的比例分别增加132.44%和91.45%，MWD值分别增加89.79%和66.87%。这主要得益于土壤交换性Ca^{2 +}、Mg^{2 +}、K⁺和Na⁺，以及铁铝氧化物含量的改善对大团聚体形成与稳定的驱动作用。OF_N处理较CF_N处理显著减少了氮肥投入量（261 vs. 480 kg N hm⁻² yr⁻¹），但所测定的各指标均未表现出显著差异。
结论尽管长期（12年）秸秆与秸秆生物炭等碳量还田配合优化施氮提高土壤有机碳含量、改善土壤团聚体结构的效果存在差异，但均显著优于单施氮肥处理。研究结果可为华北平原石灰性潮土农田碳氮协同调控策略促进土壤健康提供理论支撑。

Abstract:
Objective The objective of this study was to assess the effect of different organic materials coupled with optimized nitrogen (N) application on soil organic carbon (SOC) and its labile fractions, as well as the formation and stabilization mechanism of soil aggregates in calcareous aquic soil.
Method Based on a long-term experiment, the effects and mechanisms of SOC sequestration were studied in four treatments. They are conventional N application (CP_N), optimized N application (OF_N), straw combined with optimized N application (S_N) and straw biochar combined with optimized N application (BC_N).
Result BC_N enhanced SOC hugely among the four fertilization treatments, reaching 18.68 g kg^-1, followed by S_N, CF_N and OF_N treatment. Compared with CF_N treatment, organic materials combined with optimized N application could significantly increase the contents of microbial biomass carbon (MBC), dissolved organic carbon (DOC), particle organic carbon (POC) and easily oxidized organic carbon (EOC) by 128.26%, 96.62%, 219.72% and 45.42%, respectively. At the same time, the proportion of aggregates > 0.25 mm and the mean weight diameter (MWD) were significantly increased. The proportion of aggregates > 0.25 mm of S_N and BC_N were increased by 132.44% and 91.45%, and the MWD values were increased by 89.79% and 66.87%, respectively. This is mainly due to the increase in soil exchangeable Ca^{2 +}, Mg^{2 +}, K⁺ and iron-aluminum oxides content, as well as the decrease in soil exchangeable Na⁺, which were positively correlated with the formation and stability of macroaggregates. However, there was no significant difference on the measured indicators between the OF_N and CF_N treatment, but the amount of N input was significantly reduced (261 vs. 480 kg N hm^-2 yr^-1).
Conclusion Although there were differences in the effects of long-term (12-years) straw and straw biochar applied with equal carbon combined with optimized N input on the enhancement of SOC and improvement of soil aggregate structure, they were significantly better than those of N application alone. The results could provide theoretical support for co-regulation strategy of carbon and N to promote soil health in calcareous fluvo-aquic soils of the North China Plain.

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