原生类有机覆盖物的不同施氮处理对绿地土壤肥力和细菌群落的影响

Effects of Different Nitrogen Treatments with Natural Organic Mulch on the Fertility and BacterialCommunities in Green Soils

关键词:  风景园林  园林绿化垃圾  原生类有机覆盖物  施氮处理  土壤肥力  细菌群落  绿地土壤健康

Key words:  landscape architecture  green-wast  natural organic mulch  nitrogen treatment  soil fertility  bacterial community  health of green soi

摘要:

为了解高碳氮比的园林绿化垃圾直接粉碎后用作原生类有机覆盖物对绿地土壤覆盖效果的影响，以香樟枝条粉碎木片作为原生类有机覆盖物，研究不同 施氮处理覆盖后对上海辰山植物园土壤肥力和细菌群落的影响，结果表明：木片直接覆盖提高了土壤的碳氮比、肥力及细菌群落多样性和物种丰富度。覆盖一个 月后，土壤有机质、有效磷和速效钾含量与对照差异显著(P<0.05)，但覆盖对水解性氮含量影响不显著。与木片直接覆盖相比，施氮处理降低了土壤碳氮比、有 机质和有效磷含量，且该趋势随施氮量的增加而增大，但在覆盖前期施氮处理均显著提高了土壤水解性氮和速效钾含量(P<0.05)，在覆盖后期差异变小。在施氮 量为0.5~2.0 kg/m3范围内，施氮量为0.5 kg/m3对提高土壤肥力和细菌物种丰富度的效果最好。在同等施氮量时，仅在覆盖前期氮肥表施比混施能显著降低 土壤碳氮比，显著提高土壤水解性氮含量(P<0.05)，但在覆盖后期差异不显著；对于其他土壤性质，表施与混施差异不显著，但混施更有利于提高土壤有效磷含 量和细菌物种丰富度。土壤细菌群落的优势菌门是放线菌门、变形菌门和酸杆菌门，不同施氮处理均提高了土壤变形菌门的物种丰度，但对土壤细菌优势物种组 成无显著影响。冗余分析(RDA)表明有机质含量是影响细菌群落结构的主要环境因子。鉴于中国城市绿地土壤有机质含量普遍偏低的情况，将园林绿化垃圾直接 粉碎后用作原生类有机覆盖物引起土壤碳氮比失衡的潜在风险小，能有效提高绿化土壤质量和园林绿化垃圾利用率，以在覆盖前期混施不超过0.5 kg/m3的氮肥 最有利于绿

Abstract:

Organic mulch treatment, as one of the primary methods for the resource utilization of green waste, mainly has three disposal methods, including natural, fermented, and dyed mulch. The natural organic mulch crushed from green waste can be covered directly on the soil. This method is simple and easy to implement. It may greatly improve the resource-utilization efficiency of green waste. However, natural organic mulch generally has a high carbon-tonitrogen (C/N) ratio, leading to some doubts about whether direct mulching affects the mulching efficiency. The crop straw returning to the field with a high C/N ratio often adopts the method of supplementing nitrogen fertilizer to improve the coverage efficiency, but there is still a lack of relevant research on the utilization of the organic mulch in green spaces. For this purpose, in this study, crushed wood chips from camphor branches with a high C/N ratio were selected as natural organic mulch. Then, these wood chips with different nitrogen treatments were covered on the soil of Shanghai Chenshan Botanical Garden to investigate the effects of different nitrogen treatments on soil fertility and bacterial communities. The results showed that direct coverage with wood chips increased the soil C/N ratio and fertility, as well as the diversity of the bacterial community and species richness. After one month of coverage, the contents of soil organic matter, available phosphorus, and available potassium reached significant differences (P<0.05) compared with the control, but the content of hydrolyzable nitrogen did not change significantly. Compared with the direct coverage of wood chips, the treatment with nitrogen application caused a reduction of the soil C/N ratio and the contents of organic matter and available phosphorus, while the decreasing effect was enhanced with the increase of nitrogen application rate. However, the treatment with nitrogen application significantly increased the contents of hydrolytic nitrogen and available potassium in the early stage of coverage (P<0.05), while the difference decreased in the later stage of coverage. Within the nitrogen application range of 0.5~2.0 kg/m3, the nitrogen application rate of 0.5 kg/m3 was most effective in improving the soil fertility and richness of bacterial species. At the same nitrogen application rate, the surface application of nitrogen fertilizer only reduced the soil C/N ratio significantly while increasing the soil hydrolytic nitrogen content (P<0.05) in the early stage of mulching compared to mixed application, but the difference was not significant in the later stage of mulching. Although there is no significant difference in other soil properties between surface application and mixed application, the mixed application of nitrogen fertilizer is more conducive to improving the content of soil available phosphorus and the richness of bacterial species. As for bacterial communities, the dominant phyla in the soils are Actinobacteria, Proteobacteria, and Acidobacteria. Different nitrogen treatments increased the species abundance of Proteobacteria in soil, but had no significant effect on the composition of dominant bacterial species. Redundancy analysis (RDA) showed that the content of organic matter was the main environmental factor affecting the structure of the bacterial community. Due to the low content of organic matter in the urban greening soils in China, direct coverage of natural organic mulch has little risk of carbon/nitrogen imbalance in soils. The impact of nitrogen application on the coverage of natural organic matter mainly occurs in the early stage of coverage, but it has little effect in the later stage. Therefore, direct crushing and mulching green waste could not only improve the soil quality, but also greatly improve the resource utilization rate of green waste. Thus, the mixed application of nitrogen fertilizer not exceeding 0.5 kg/m3 in the early stage of naturally mulching is most beneficial for the healthy cultivation of green soil, which provides a reference for the refined maintenance and management of urban green spaces