双季稻田土壤微生物群落对连续5年施有机肥和石灰的响应差异

Response of Microbial Community in Purple Mud of Double-cropped Rice Fields to 5-year Continuous Application of Organic Amendment and Liming

    摘要
  • 摘要:
      目的  土壤微生物是土壤健康的敏感“指示器”，但不同的土壤微生物类群对连续施用有机肥和石灰的响应规律及不同指标的敏感性仍不明确。
      方法  本文选取中亚热带双季稻区的紫泥田作为研究对象，研究连续5年施用有机肥或石灰后，土壤微生物“黑箱指标”（微生物生物量碳氮、微生物熵和土壤呼吸速率）和土壤活体微生物（PLFAs）组成的响应规律与差异。
      结果  与对照相比，连续施用有机肥后，土壤微生物生物量碳（MBC）、氮（MBN）含量和土壤呼吸速率分别提高37%、28%和44% ~ 59%，微生物多样性也显著提高，土壤细菌结构发生改变，尤其是革兰氏阴性菌（G−）的PLFAs绝对量提高了100%，但真菌类群的响应不敏感。相反，连续施用石灰5年后，土壤微生物生物量碳、氮含量均呈下降趋势，微生物熵和土壤呼吸速率分别降低11%和26% ~ 52%，微生物多样性显著降低，细菌、放线菌和绝大多数真菌类群PLFAs绝对量下降30% ~ 58%。相关性分析结果表明，土壤有机质含量与土壤微生物总PLFAs和细菌PLFAs含量呈显著正相关关系；而土壤pH仅与Simpson多样性指数呈显著正相关关系。施有机肥显著提高了土壤有机质含量进而导致细菌MBC、MBN、G−和土壤呼吸速率显著增加；而施石灰后土壤微生物群落结构及活性降低与土壤pH有关。
      结论  连续5年施用有机肥、石灰后，土壤微生物指标分别表现为正面、负面响应。与“黑箱指标”相比，某些特定微生物类群（如G−）的敏感性指数值更高，在土壤健康评价中极具应用潜力。

     

    Abstract:
      Objective  Soil microorganism is a sensitive indicator of change in soil health, but how microbial groups and the sensitivity of the different indicators in paddy soils responding to continuous application of organic amendment and liming is still unknown.
      Method  The purple mud of double-cropped rice fields in mid-subtropics was selected. The “black box” indices of soil microorganism (soil microbial biomass carbon and nitrogen, microbial entropy, and soil respiration) and soil living microorganisms (PLFAs) structure of different microbial groups in response to 5-year continuous applying organic amendment or liming were studied.
      Result  Comparing to the control, the soil microbial biomass carbon (MBC), nitrogen (MBN), and soil respiration rate in organic amendment treatment were elevated by 37%, 28% and 44%-59%, respectively. Meanwhile the indices of soil microbial diversity were enhanced. The soil bacterial structure was changed, especially for the PLFAs absolute abundance of G− increased by 100%, while the fungal groups were insensitive to the organic amendment. However, the soil microbial entropy and soil respiration rate was reduced by 11% and 26%-52%, respectively, as well as the decreased indices of soil microbial diversity after the liming. The absolute abundance of bacteria, actinomycetes, and most fungal groups were reduced by 30%-58%. The correlation analysis showed that soil organic matter content was significantly and positively correlated with soil microbial total PLFAs and bacterial PLFAs. However, there was a significant positive correlation between soil pH and Simpson diversity index. This study revealed that organic fertilizer application significantly increased soil organic matter content, resulting in significantly increased bacterial MBC, MBN, G− and soil respiration rate. The decrease of soil microbial community structure and activity after lime application was related to soil pH.
      Conclusion  As a whole, the soil microbial indices revealed a positive and a negative response to 5-year continuous application of organic amendment and liming, respectively. Specific microbial groups (such as G−) were higher than those of “black box” indices, which showed great potential in soil health assessment tools.

     

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