The root-knot nematode (Meloidogyne spp.) is an obligate plant parasite and is one of the largest threats to the Australian sweetpotato industry, causing crop losses of up to 57% of marketable yield. In this study, two potential fungal biocontrol agents were encapsulated in alginate granules and their nematophagous activity was assessed in a laboratory-based microcosm experiment. Both species of fungi significantly reduced numbers of root-knot nematodes in red ferrosol soil. A greater reduction was observed in untreated field soil prior to introduction of root-knot nematodes and fungal biocontrol agents compared to soil that had been heat-sterilised. In a ten-week glasshouse experiment, no significant difference in the root-knot nematode populations in sweetpotato roots and soil was found between fungal biocontrol agent and control treatments. There was a trend towards an increase in the sweetpotato storage root weight and reduction in storage root damage in fungal biocontrol agent compared to control treatments, and both yield and damage levels were similar to those achieved from the use of chemical nematicide treatments. These results demonstrate the need for greater understanding of the interactions between soil biological populations and introduced nematophagous fungi if effective biocontrol is to be consistently achieved with these bioagents under field conditions.

Water conveyance channels in cold and arid regions pass through several saline-alkali soil areas. Canal water leakage exacerbates the salt expansion traits of such soil, damaging canal slope lining structures. To investigate the mechanical properties of saline clay, this study conducted indoor tests, including direct shear, compression, and permeation tests, and scanning electron microscopy (SEM) analysis of soil samples from typical sites. This study aims to elucidate the impact of various factors on the mechanical properties of saline clay from a macro-micro perspective and reveal its physical mechanisms. A prediction model is formulated and validated. The findings indicate the following: (1) Cohesion in direct shear tests has a linear negative correlation with water content and a positive correlation with dry density and initially decreases with increasing salt content until 2%, after which it increases. The internal friction angle initially increases and then decreases with increasing water content, reaching a peak at the optimal water content, and then gradually increases with dry density while initially decreasing, followed by an increase in salt content, stabilizing thereafter. Water content, dry density, or salt content chiefly affect cohesion by influencing electrostatic attraction, van der Waals forces, particle cementation, and valence bonds at particle contact points. (2) Compression tests reveal a linear positive correlation between the compression coefficient and water content, a negative correlation with dry density, and a stepwise linear correlation with salt content, peaking at 2%. The compression index decreases with increasing water content and dry density, following a trend similar to that of the compression coefficient with increasing salt content. The rebound index shows a linear negative correlation with water content and dry density, transitioning from a negative to a positive correlation at 2% salt content. Scanning electron microscopy analysis revealed particle flattening and increased aggregation with increasing consolidation pressure, reducing compressibility. Large pores and three-dimensional porosity have the greatest influence on soil compressibility. (3) Permeability tests reveal an exponential negative correlation between the permeability coefficient and dry density. As the dry density increases, the particle arrangement becomes denser, decreasing the pore quantity, with micropores disproportionately impacting the permeability coefficient. An increase in salinity initially increases the permeability coefficient before it decreases. The boundary point of the 2% salt content divides the effect of salt ions from promoting free water flow to blocking seepage channels, with the proportion of micropores being the primary influencing factor. (4) Employing statistical theory and machine learning algorithms, dry density, water content, and salinity are used to predict mechanical index values. The improved particle swarm optimization-support vector regression (PSO-SVR) model has high accuracy and general applicability. These findings offer insights for the construction and upkeep of open channel projects in arid regions.

Crude oil contamination has inflicted severe damage to soil ecosystems, necessitating effective remediation strategies. This study aimed to compare the efficacy of four different techniques (biostimulation, bioaugmentation, bioaugmentation + biostimulation, and natural attenuation) for remediating agricultural soil contaminated with crude oil using soil microcosms. A consortium of previously characterized bacteria Xanthomonas boreopolis, Microbacterium schleiferi, Pseudomonas aeruginosa, and Bacillus velezensis was constructed for bioaugmentation. The microbial count for the constructed consortium was recorded as 2.04 +/- 0.11 x 108 CFU/g on 60 d in augmented and stimulated soil samples revealing their potential to thrive in chemically contaminatedstress conditions. The microbial consortium through bioaugmentation + biostimulation approach resulted in 79 +/- 0.92% degradation of the total polyaromatic hydrocarbons (2 and 3 rings - 74%, 4 and 5 rings - 83% loss) whereas, 91 +/- 0.56% degradation of total aliphatic hydrocarbons (C8-C16 - 90%, C18-C28 - 92%, C30 to C40 88% loss) was observed in 60 d. Further, after 60 d of microcosm treatment, the treated soil samples were used for phytotoxicity assessment using wheat (Triticum aestivum), black chickpea (Cicer arietinum), and mustard (Brassica juncea). The germination rates for wheat (90%), black chickpea (100%), and mustard (100%) were observed in 7 d with improved shoot-root length and biomass in both bioaugmentation and biostimulation approaches. This study projects a comprehensive approach integrating bacterial consortium and nutrient augmentation strategies and underscores the vital role of innovative environmental management practices in fostering sustainable remediation of oil-contaminated soil ecosystems. The formulated bacterial consortium with a nutrient augmentation strategy can be utilized to restore agricultural lands towards reduced phytotoxicity and improved plant growth.

The response of microbial communities to the predicted rising temperatures in alpine regions might be an important part of the ability of these ecosystems to deal with climate change. Soil microbial communities might be significantly affected by elevated temperatures, which influence the functioning of soils within high-alpine ecosystems. To evaluate the potential of the permafrost microbiome to adapt to short-term moderate and extreme warming, we set up an incubation experiment with permafrost and active soil layers from northern and southern slopes of a high-alpine mountain ridge on Muot da Barba Peider in the Swiss Alps. Soils were acclimated to increasing temperatures (4-40 degrees C) for 26 days before being exposed to a heat shock treatment of 40 degrees C for 4 days. Alpha-diversity in all soils increased slightly under gradual warming, from 4 to 25 degrees C, but then dropped considerably at 40 degrees C. Similarly, heat shock induced strong changes in microbial community structures and functioning in the active layer of soils from both northern and southern slope aspects. In contrast, permafrost soils showed only minor changes in their microbial community structures and no changes in their functioning, except regarding specific respiration activity. Shifts in microbial community structures with increasing temperature were significantly more pronounced for bacteria than for fungi, regardless of the soil origin, suggesting higher resistance of high-alpine fungi to short-term warming. Firmicutes, mainly represented by Tumebacillus and Alicyclobacillaceae OTUs, increased strongly at 40 degrees C in active layer soils, reaching almost 50% of the total abundance. In contrast, Saccharibacteria decreased significantly with increasing temperature across all soil samples. Overall, our study highlights the divergent responses of fungal and bacterial communities to increased temperature. Fungi were highly resistant to increased temperatures compared to bacteria, and permafrost communities showed surprisingly low response to rising temperature. The unique responses were related to both site aspect and soil origin indicating that distinct differences within high-alpine soils may be driven by substrate limitation and legacy effects of soil temperatures at the field site.