Peanut yield and quality are seriously compromised by continuous monoculturing in the red soil region of southern China. Monoculturing can cause soil degradation and an increase in soil-borne diseases. This research aimed to investigate the influence of long-term peanut monocropping and different fertilization treatments on peanut growth, soil physical and chemical properties and soil microbial community. A long-term fertilization experiment established in 1996 was utilized to examine the effect of various fertilization treatments including chemical and organic fertilizers treatments. Deep 16S rRNA gene pyrosequencing highlighted changes in the abundance and structure of bacterial communities, especially of the pathogenic and beneficial bacterial communities in long term chemical fertilizer treatment in comparison to the organic manure treatment. Chemical fertilizer treatment causes a shift in bacterial community structure and decrease in diversity under the long-term monocropping in comparison to organic fertilizer. The abundance of the bacterial pathogen Ralstonia solanacearum, a causative agent of peanut wilt, was found to be associated with a loss of community diversity and loss of the peanut yield. The organic fertilizers more effectively increase microbial diversity in the soil and changed the community structure. Long-term use of the chemical fertilizer leads to a decrease in microbial diversity of the soil and an increase in R. solanacearum with associated increase of peanut wilt. The potential decrease in diversity and competition between the bacterial community and the pathogen may be a contributing factor to increased disease during long-term chemical fertilizer use.

Microplastics (MPs) enter the soil through a variety of pathways, including plastic mulching, sludge, and organic manure application. In recent years, domestic and foreign experts and scholars have been concerned about the residues and contamination of MPs in the soil of greenhouse agriculture. In this investigation, five types of MPs including low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET), and two concentrations (1% and 5%, w/w) were used in a 30-day external exposure test. Evidence of microbial enrichment was found on the surface of the MPs. The total amount of biofilm on the surface of MPs increased dramatically with increasing exposure time and MP concentrations. The polysaccharide content of extracellular polymers (EPS) in biofilms was significantly different, and the maximum PS1 (1% (w/w) PS) concentration was 50.17 mg/L. However, EPS protein content did not change significantly. The dominant bacteria on the surface of MPs with different types and concentrations were specific, and the relative abundance of Patescibacteria was significantly changed at the phylum level. At the genus level, Methylophaga, Saccharimonadales, and Sphingomonas dominated the flora of LDPE1 (1% (w/w) LDPE), PS1, and PET5 (5% (w/w) PET). The dominant bacteria decompose organic materials and biodegrade organic contaminants. According to the FAPROTAX functional prediction study, chemoheterotrophy and aerobic chemoheterotrophyplay a role in ecosystem processes such as carbon cycle and climate regulation. The application of LDPE1 has a greater impact on the carbon cycle. Plant development and soil nutrients in greenhouse agriculture may be influenced by the interaction between MPs and microorganisms in the growing area, while MP biofilms have an impact on the surrounding environment and pose an ecological hazard.

Greenhouse cultivation has expanded for years to provide vegetables for a growing population in China. It’s reported that total area of greenhouse soil has reached 4.708 million hectares in 2019. To maintain good productivity, a large quantity of fertilizers was continuously applied to the soil. Due to low nitrogen (N) use efficiency, excessive nutrients are accumulated in soil profile. As a result, greenhouse soil is often compromised by the secondary soil salinization. This paper summarized the typical characteristics of secondary salinization of greenhouse soil such as nitrate accumulation and soil acidification as a result of excessive N application. The adverse impacts of soil salinization were also reviewed on major physical, chemical and biological properties of soil. It can be found that many physiological diseases due to nutrient disorder and soil borne diseases because of changes in soil microflora, are associated with higher salt concentration in soil and the lower soil pH. To reclaim the degraded soil with high nitrate concentration, an economical and environmentally friendly approach by incorporation of appropriate amount of plant materials with high C/N ratio into the soil was discussed. It was demonstrated that biomass addition could promote humification of nitrate with the help of microorganisms.