Study of Total Bacteria and Ammonia-Oxidizing Bacteria and Ammonia-Oxidizing Archaea in Response to Irrigation with Sewage Sludge Compost Tea in Agricultural Soil

Organic amendments have been shown to improve the quality of agricultural soils. Thus, the use of sewage sludge compost tea as a fertilizer can be considered a worthy and environmentally friendly alternative as it also offers the option of recycling sludge at the same time. However, an in-depth knowledge of how the addition of this product affects soil microbial diversity is still necessary. As such, the main objective of this study was to evaluate, at a microcosm level, the effects of irrigation with sewage sludge compost tea in an olive grove soil, focusing on the changes in the total bacteria, ammonia-oxidizing bacteria (AOB), and ammonia-oxidizing archaea (AOA). For this purpose plastic pots were filled with olive grove soil, watered with different amounts of water and/or compost tea, and incubated at 21 and 35°C for a period of 90 days. Denaturing gradient gel electrophoresis (DGGE) fingerprinting, real-time PCR, and 454-pyrosequencing analysis were performed. Our results suggested that the addition of sewage sludge compost tea (liquid fertilizer) slightly increased the soil biological diversity during the incubation time which suggests that sewage sludge compost tea did not have any negative effects in the soil microbiota. Accordingly and regardless of the incubation temperature, significant changes in the soil community structure were not observed throughout the experiment, suggesting that the treated soils maintained their microbiological stability.

已有研究证实，有机改良剂可提升农田土壤质量。因此，将污泥堆肥茶（sewage sludge compost tea）用作肥料可被视为一种极具价值且环境友好的替代方案，同时还可实现污泥的资源化回收。然而，目前仍需深入了解该制剂的施用对土壤微生物多样性的具体影响。据此，本研究的核心目标是在微宇宙尺度层面，评估污泥堆肥茶灌溉对橄榄园土壤的影响，重点关注土壤总细菌、氨氧化细菌（ammonia-oxidizing bacteria, AOB）以及氨氧化古菌（ammonia-oxidizing archaea, AOA）的群落变化。为此，本研究将橄榄园土壤装入塑料盆中，设置不同梯度的清水及/或堆肥茶灌溉处理，并分别在21℃与35℃条件下培养90天。实验采用变性梯度凝胶电泳（Denaturing gradient gel electrophoresis, DGGE）指纹图谱技术、实时荧光定量聚合酶链式反应（real-time PCR）以及454焦磷酸测序（454-pyrosequencing）开展分析。研究结果显示，在培养周期内，施加污泥堆肥茶（液态肥料）可小幅提升土壤生物多样性，表明该制剂未对土壤微生物群落产生任何负面影响。据此，无论培养温度如何，实验全程均未观测到土壤群落结构发生显著变化，提示经处理的土壤维持了其微生物学稳定性。