Impacts of vegetable processing and cheese making effluent on soil microbial functional diversity, community structure, and denitrification potential of land treatment systems.

The cheese making and vegetable processing industries generate immense volumes of high-nitrogen wastewater that is often treated at rural facilities using land applications. Laboratory incubation results showed denitrification decreased with temperature in industry facility soils but remained high in soils from agricultural sites (75% at 2.1°C). 16S rRNA, phospholipid fatty acid (PLFA), and soil respiration analyses were conducted to investigate potential soil microbiome impacts. Biotic and abiotic system factor correlations showed no clear patterns explaining the divergent denitrification rates. In all three soil types at the phylum level, Actinobacteria, Proteobacteria, and Acidobacteria dominated, whereas at the class level, Nitrososphaeria and Alphaproteobacteria dominated, similar to denitrifying systems such as wetlands, wastewater resource recovery facilities, and wastewater-irrigated agricultural systems. Results show that potential denitrification drivers vary but lay the foundation to develop a better understanding of the key factors regulating denitrification in land application systems and protect local groundwater supplies. PRACTITIONER POINTS: Incubation study denitrification rates decreased as temperatures decreased, potentially leading to groundwater contamination issues during colder months. The three most dominant phyla for all systems are Actinobacteria, Proteobacteria, and Acidobacteria. The dominant class for all systems is Nitrosphaeria (phyla Crenarchaeota). No correlation patterns between denitrification rates and system biotic and abiotic factors were observed that explained system efficiency differences.

Effects of simulated nitrogen deposition on soil microbial community diversity in coastal wetland of the Yellow River Delta.

Due to the enhancement of human activities on the global scale, the total amount of atmospheric nitrogen (N) deposition and the rate keep increasing, which seriously affect the structure and function of terrestrial ecosystems. In order to study the effects of N deposition on the soil structure and function of coastal saline wetlands, we established a long-term nitrogen deposition simulation platform in 2012 in the Yellow River delta (YRD). Herein, we analyzed the composition and diversity of the soil microbial community under different N deposition treatments (LNN, MNN and HNN, which stand for 50 kg N ha-1 yr-1, 100 kg N ha-1 yr-1, and 200 kg N ha-1 yr-1) and in a water-only control (CK). The results showed that with the increasing level of N deposition, α-diversity (Shannon and Simpson indices) decreased significantly, and the composition of the microbial community changed. At the phylum level, compared with CK, the relative abundance of Chloroflexi increased significantly under the treatment of HNN (P = 0.002), but the relative abundance of Chlorobi (P = 0.013) and Verrucomicrobia (P = 0.035) decreased significantly. At the genus level, compared with CK, the relative abundance of Bacillus (P = 0.01) and Halomonas (P = 0.042) increased significantly with HNN treatment. Bacillus and Nitrococcus showed a significant correlation with soil NH4+-N. The results suggest that the response of microorganisms to N deposition treatments varied by the concentration, and the deposition of a high concentration would increase the nutrients in the soil, but reduce the diversity of soil microorganisms, causing a negative impact on the coastal wetland ecosystem of the YRD.