Purpose

Intensified livestock system produced large amount of bio-waste, and improper disposal of livestock manure has led to severe environmental consequences. However, knowledge about the time-dependent changes of manure-derived nitrate and soil bacterial diversity along the soil profiles is limited.

Materials and methods

Vertical variation of soil bacterial diversity and composition in a manure-amended maize field and adjacent non-manured woodland was investigated using high-throughput sequencing technique in spring and autumn along a 1-m profile depth. The soil is classified as aquic inceptisol with a bulk density of 1.31 g cm⁻³, and a sandy loam texture.

Results

The results showed that significant higher amount of nitrate (up to 172.13 mg kg⁻¹) was detected along the soil profile loaded with cattle manure compared with the adjacent non-manured woodland. Soil δ¹⁵N-NO₃⁻ composition from maize field fall between + 5 and 25‰, while those from woodland fall between − 5 and 15‰. No significant difference in bacterial richness between the two land uses was found, while clear separation of bacterial structure was detected even to the deep soil layers. Canonical correspondence analysis showed that soil organic matter, C/N ratio, nitrate content, pH, and moisture were the major factors influencing the variance of bacterial community composition. Bacterial networks in the maize field harbor more modules than those in the adjacent woodland. Negative standardized effect size measure of mean nearest taxon distance in the soils tended to be more phylogenetically clustered than expected by chance, and was more likely to be clustered along the depth.

Conclusions

These findings suggested that soil bacterial β diversity was strongly affected by multi-nutrient properties in terms of high livestock manure load, and had important implications for assessing the environmental impacts on belowground biodiversity in sandy loam soils.

中文翻译：

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粪肥处理玉米田及邻近林地土壤硝态氮和细菌多样性沿土壤剖面的变化

目的

牲畜系统集约化生产大量生物废物，牲畜粪便处理不当导致严重的环境后果。但是，关于粪便来源的硝酸盐和土壤细菌多样性沿土壤剖面随时间变化的知识是有限的。

材料和方法

使用高通量测序技术，在春季和秋季沿1 m剖面深度调查了在改良肥料的玉米田和附近非耕地林地中土壤细菌多样性和组成的垂直变化。土壤被归类为含水感受态醇，堆积密度为1.31 g cm ^-3，具有砂壤土质地。

结果

结果表明，与相邻的未耕地林地相比，沿着牛粪负载的土壤剖面中检测到的硝酸盐量明显更高（最高172.13 mg kg ^-1）。土壤δ ¹⁵ N-NO ₃ ^-玉米田的土壤成分介于+ 5和25‰之间，而林地的土壤成分介于− 5和15‰之间。两种土地利用之间细菌丰富度没有发现显着差异，而即使在深层土壤中，细菌结构也被清楚地分离出来。典型的对应分析表明，土壤有机质，碳氮比，硝酸盐含量，pH和水分是影响细菌群落组成变化的主要因素。玉米田中的细菌网络比相邻林地中的细菌网络拥有更多的模块。对土壤中平均最近分类群距离的负标准化效应大小度量往往比偶然预期的更系统地聚类，并且更有可能沿深度聚类。

结论

这些发现表明，就高牲畜粪便负荷而言，土壤细菌β多样性受到多种营养特性的强烈影响，并且对评估砂壤土中地下生物多样性的环境影响具有重要意义。