紫色土氨氧化作用及氨氧化微生物对铵态氮施用量的响应

Effect of Ammonium Nitrogen Application on Ammonia Oxidation and Ammonia-Oxidizing Microorganisms in Purple Soil

    摘要
  • 摘要:
    目的 氨氧化过程是硝化作用的限速步骤，明确铵态氮肥施用量对土壤硝化过程、硝化微生物丰度及群落结构的影响。
    方法 以钙质紫色土为研究对象，采用盆栽试验方法，设置不施氮肥（CK）、低量施氮（N1，0.1 g kg−1）、常规施氮（N2，0.2 g kg−1）和高量施氮（N3，0.4 g kg−1）4个处理，通过测定土壤基本理化性质、硝化势、氨氧化微生物基因丰度及群落结构，探讨铵态氮肥施用量对钙质紫色土硝化过程及相关微生物的影响。
    结果 随着铵态氮肥施用量的增加，土壤pH值呈现显著下降趋势（P < 0.05），N1、N2和N3处理较CK分别下降了0.4、0.7和1.4个单位。土壤全氮、铵态氮和碱解氮含量显著升高（P < 0.05），施肥处理较CK分别提高20.5% ~ 180.8%、46.1% ~ 93.4%、150.2% ~ 821.6%。N2处理下土壤硝化势最高，较CK和N1处理分别提升了34.2%和66.1%（P < 0.05）。氨氧化古菌（AOA）和氨氧化细菌（AOB）的amoA基因拷贝数均随氮肥用量增加呈先升后降的趋势。群落结构分析显示，钙质紫色土中AOA的优势菌门为泉古菌门（Crenarchaeota）和奇古菌门（Thaumarchaeota）。AOB的优势菌门为变形菌门（Proteobacteria），优势菌属为亚硝化螺菌属（Nitrosospira）。施肥引起的土壤因子变化中，土壤全氮、铵态氮和硝态氮含量是影响AOA和AOB群落结构的主要因子。进一步分析表明，AOB amoA基因丰度与土壤硝化势呈极显著正相关关系，表明AOB在钙质紫色土硝化过程中具有重要的生态功能。
    结论 高氮量施肥在提高土壤养分含量的同时导致土壤pH降低，进而显著改变了氨氧化微生物的丰度和群落结构。在不同铵态氮肥用量条件下，氨氧化细菌（AOB）在钙质紫色土氨氧化过程中的作用显著大于氨氧化古菌（AOA）。

     

    Abstract:
    Objective Nitrification is a key process in soil nitrogen (N) transformation, in which ammonia oxidation serves as the rate-limiting step. Clarifying the effects of ammonium N fertilizer application on the soil nitrification process, as well as on the abundance and community structure of ammonia-oxidizing microorganisms, is essential for improving N use efficiency in farmland and optimizing N fertilizer management.
    Method In this study, calcareous purple soil was used as the test soil, and a pot experiment was conducted with four treatments: no N application (CK), low N fertilizer (N1, 0.1 g kg−1), regular N fertilizer (N2, 0.2 g kg−1), and high N fertilizer (N3, 0.4 g kg−1). Soil physicochemical properties, potential nitrification rate, and the gene abundance and community composition of ammonia-oxidizing microorganisms were analyzed to explore the effects of ammonium N fertilizer rates on the nitrification process and microbial responses in purple soil.
    Result With increasing application rates of ammonium N fertilizer, soil pH showed a significant decreasing trend (P < 0.05), with reductions of 0.4, 0.7, and 1.4 units under the N1, N2 and N3 treatments, respectively. Compared to CK. The contents of total nitrogen (TN), ammonium nitrogen (NH4+-N) and alkali-hydrolyzable N (AN) significantly increased (P < 0.05), ranging from 20.5% - 180.8%, 46.1% - 93.4%, and 150.2% - 821.6% across fertilization treatments, respectively. The highest soil nitrification potential was observed under the N2 treatment, which was 34.2% and 66.1% higher than those of the CK and N1 treatments, respectively (P < 0.05). The amoA gene copy numbers of both ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) exhibited an increasing-then-decreasing trend with rising N application rates. Community structure analysis revealed that the dominant AOA phyla in purple soil were Crenarchaeota and Thaumarchaeota, while the dominant AOB phylum was Proteobacteria, with Nitrosospira being the dominant genus. Among the soil parameters altered by fertilization, TN, NH4+-N and NO3−-N were the main factors shaping the community structures of AOA and AOB. Further correlation analysis showed a highly significant positive relationship between AOB amoA gene abundance and soil nitrification potential, indicating that AOB play a predominant role in the nitrification process of purple soil.
    Conclusion High N fertilization enhanced soil nutrient levels but also decreased pH, thereby significantly altering the abundance and community structure of ammonia-oxidizing microorganisms. Under different ammonium N fertilizer application levels, AOB contributed more significantly than AOA to the ammonia oxidation process in calcareous purple soil.

     

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