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Against the background of increasing salinisation of land, the use of environmentally friendly plant growth-promoting bacteria (PGPB) resources for soil improvement is particularly important. The aim of this study was to investigate the effects of Pseudomonas cedrina DY1-3 on maize seedling growth, soil physico-chemical properties, and bacterial community structure. The study also evaluates the effects of this microbial agent on plant growth and saline soil improvement, providing theoretical references for microbial agents in promoting plant growth and improving saline soils. We found that there were significant differences between arable and saline soils in terms of soil physico-chemical properties and bacterial community structural composition, and that total salt was the main environmental factor influencing microbial communities. In both arable and saline soils, the application of DY1-3 bacterial suspension had a significant positive effect on the growth of maize plants and bacterial community richness. In arable soil, it could promote the growth of maize seedlings and significantly increase the Shannon and Simpson index, and AK was a key factor influencing the bacterial community. In saline soil, it could alleviate the mitigation stress and promote the growth of maize seedlings and cause a significant increase in Shannon’s and Chao1 index, and the application of DY1-3 and potting could cause a significant decrease in total salt. In addition, DY1-3 and maize plants acting together in the soil can better improve the saline soil. The above results indicate that DY1-3 has potential for saline soil improvement and crop yield enhancement.

Unreasonable cultivation methods and management measures have led to widespread obstacles in tobacco continuous cropping in planting areas, resulting in reduced tobacco yield and soil degradation. Therefore, intercropping tobacco with other crops is an effective strategy to improve continuous cropping barriers. In this study, flue-cured tobacco NC102 and conventional planting varieties of Salvia miltiorrhiza were used as materials, and four treatments of flue-cured tobacco monoculture (CK), flue-cured tobacco, and Salvia miltiorrhiza at a ratio of 1:1 (TS11), 2:2 (TS22), and 2:3 (TS23), respectively, were set up to study their effects on soil microorganisms, physical and chemical properties, and yield and quality of flue-cured tobacco. The results showed that intercropping Salvia miltiorrhiza increased the number of soil bacteria and actinomycetes, decreased the number of fungi, and increased the activity of urease and sucrase. The content of available nitrogen and available phosphorus in intercropping Salvia miltiorrhiza soil was significantly higher than that of the flue-cured tobacco monoculture, while the content of available potassium was lower than that of the flue-cured tobacco monoculture. The soil environment was more conducive to the growth of flue-cured tobacco. Compared with the flue-cured tobacco monoculture, the proportion of superior tobacco in intercropping Salvia miltiorrhiza increased by 2.2–3.4%, and the ratio of potassium to chlorine in leaves of different parts of flue-cured tobacco increased by 12.3–75.0%. The content of total sugar and soluble sugar in middle and upper leaves of intercropping flue-cured tobacco was higher than that of the flue-cured tobacco monoculture, which improved the quality of flue-cured tobacco. From the analysis of the chemical composition of tobacco leaves, TS11 (flue-cured tobacco and Salvia miltiorrhiza intercropping row ratio of 1:1) had the best treatment effect, potassium content, total sugar, reducing sugar content, and potassium chloride ratio of flue-cured tobacco were the highest, the chlorine content was the lowest, and the quality was better than other treatments. From the analysis of total output value, the total output value of TS22 (flue-cured tobacco and Salvia miltiorrhiza intercropping row ratio of 2:2) was higher than that of other intercropping treatments. In 2018 and 2019, the total output value increased by 21.3% and 22.4%, respectively, compared with the flue-cured tobacco monoculture. The intercropping advantage was obvious, and the treatment effect was the best.

The soil nematode community plays an important role in ecosystem services. The objective of this study was to assess the effect of Super-high density (SHD) olive orchards on the nematode community in five sites with different soils, climates, and cultivars. At each site, the SHD management system was compared to the adjacent olive orchard traditional (TRAD) system, in which the same soil management and phytosanitary measures were applied. Soil management was assessed by total organic carbon content (TOC), while the soil nematode community was evaluated using the nematode taxa abundances and soil nematode indicators. TOC was significantly decreased in the SHD olive orchard system compared to TRAD in the sites characterized by conventional tillage and mineral fertilization. The two-way ANOSIM analysis on nematode abundance showed no difference between the two olive management methods, instead showing only a significant difference per site mainly due to variabilities in plant-parasitic nematode assemblage. However, a negative impact of SHD management was evident in environments stressed by summer droughts and conventional tillage: the ratio of obligate plant-parasites to bacterivores and fungivores (Pp/(B+F)) was significantly higher in SHD than in the TRAD olive orchard system, and the prey-to-predator θ mass ratio showed the lowest values in the sites under organic fertilization or green manure. The canonical correspondence analysis showed that the free-living nematodes were only slightly affected by SHD olive orchards; instead, the presence of plant-parasitic nematodes families such as Telotylenchidae, Paratylenchidae, Meloidogynidae, and Criconematidae was favored, in comparison to Longidoridae, Heteroderidae, and Pratylenchidae.

Polychlorinated biphenyls (PCBs) belong to the organic pollutants that are toxic to humans and harmful to environments. Numerous studies dealing with the impact of PCBs on soil microorganisms have focused on bacterial communities. The effects of PCBs on fungal communities in three different PCB-polluted soils from former industrial sites were investigated using high-throughput sequencing of the internal transcribed spacer 1 region. Significant differences in fungal alpha diversity were observed mainly due to soil physico-chemical properties. PCBs only influenced the richness of the fungal communities by increasing it. Fungal composition was rather strongly influenced by both PCBs and soil properties, resulting in different communities associated with each soil. Sixteen Ascomycota species were present in all three soils, including Stachybotrys chartarum, Fusarium oxysporum, Penicillium canescens, Penicillium chrysogenum,Penicillium citrosulfuratum and Penicillium brevicompactum, which are usually found in PCB-polluted soils, and Fusarium solani, Penicillium canescens, Penicillium citrosulfuratum and Penicillium chrysogenum, which are known PCB degraders. This study demonstrated that PCBs influence the richness and the composition of fungal communities. Their influence, associated with that of soil physico-chemical properties, led to distinct fungal communities, but with sixteen species common to the three soils which could be considered as ubiquitous species in PCB-polluted soils.

Sugarcane cultivation in Japan has not yet focused on suppressing plant-parasitic nematodes. For proper nematode management, it is essential to know the spatial distribution of economically important plant-parasitic nematodes and free-living nematodes that play important roles in terrestrial ecosystems. We aimed to reveal nematode fauna and soil properties in 85 sugarcane fields of three major sugarcane producing islands in Japan, and to examine their relationship by using the mixed-effect model and by visualizing the spatial distributions using the inverse distance weighting (IDW) approach. The nematode community structures were analyzed by non-metric multidimensional scaling (NMDS). Among plant-parasitic nematodes in sugarcane, the root-lesion nematodes (Pratylenchus sp.) and the stunt nematodes (Tylenchorhynchus sp.) were widely distributed in these islands, yet the abundance and the species varied geospatially. Soil pH was significantly correlated with the abundance of Pratylenchus and Tylenchorhynchus species. The abundance of Pratylenchus and Tylenchorhynchus species were significantly correlated with soil pH. The abundance of Pratylenchus was significantly correlated with the abundance of free-living nematodes, the number of free-living nematode species, and exchangeable cation K+, as were the abundance of Tylenchorhynchus to the clay content and that of non-Tylenchorhynchus. This study also revealed that the three islands had different nematode faunas, which were explained especially by soil pH, texture, and exchangeable basic cations.