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Balancing mechanical and corrosion performance is a decisive factor in the use of high entropy and medium entropy alloys (H & MEAs) as advanced engineering structural materials. This study investigates the microstructure of Fe77.3-xMnxSi9.1Cr9.8C3.8 (x = 14, 23.2) HEAs by combining experiments and first-principles calculations to elucidate the effects of adjusting Mn content on the mechanical and corrosion properties of FCC and FCC + HCP phases. The results demonstrate that HEAs with low Mn content exhibit a single FCC phase, whereas increasing Mn content not only precipitates the HCP phase but also refines the grain size. The yield strength, compressive fracture strength, work hardening index, and plasticity of Fe77.3-xMnxSi9.1Cr9.8C3.8 (x = 14, 23.2 at.%) HEAs are 1300 and 1526 MPa, 2380 and 2332 MPa, 0.42 and 0.36, 16.7% and 16%, respectively. Both HEAs exhibit superior electrochemical and salt spray corrosion performance compared to 304 stainless steels, with the Fe63.3Mn14Si9.1Cr9.8C3.8 alloy performing the best, exhibiting a self-corrosion potential of −0.523V and a self-corrosion current density of 2.605 × 10−6 A cm−2. The excellent corrosion resistance of Fe63.3Mn14Si9.1Cr9.8C3.8 can be attributed to the moderate grain size, resulting in excellent passivation film characteristics, and the lower Mn content, leading to a higher Cr2O3 content in the passivation film. First-principles calculations reveal that Fe63.3Mn14Si9.1Cr9.8C3.8 has a lower density of states number at the Fermi level (i.e., Fe63.3Mn14Si9.1Cr9.8C3.8 is 214.145eV, Fe54.1Mn23.2Si9.1Cr9.8C3.8 is 337.077eV), a wider pseudogap width, higher work function (5.700ev, 5.189ev), and better stability. Additionally, there exists a strong trade-off between corrosion and mechanical properties due to the influence of the HCP phase and grain size.

Osmotic and ionic induced salt stress suppresses plant growth. In a previous study, Enterobacter ludwigii B30, isolated from Paspalum vaginatum, improved seed germination, root length, and seedling length of bermudagrass (Cynodon dactylon) under salt stress. In this study, E. ludwigii B30 application improved fresh weight and dry weight, carotenoid and chlorophyll levels, catalase and superoxide dismutase activities, indole acetic acid content and K+ concentration. Without E. ludwigii B30 treatment, bermudagrass under salt stress decreased malondialdehyde and proline content, Y(NO) and Y(NPQ), Na+ concentration, 1-aminocyclopropane-1-carboxylate, and abscisic acid content. After E. ludwigii B30 inoculation, bacterial community richness and diversity in the rhizosphere increased compared with the rhizosphere adjacent to roots under salt stress. Turf quality and carotenoid content were positively correlated with the incidence of the phyla Chloroflexi and Fibrobacteres in rhizosphere soil, and indole acetic acid (IAA) level was positively correlated with the phyla Actinobacteria and Chloroflexi in the roots. Our results suggest that E. ludwigii B30 can improve the ability of bermudagrass to accumulate biomass, adjust osmosis, improve photosynthetic efficiency and selectively absorb ions for reducing salt stress-induced injury, while changing the bacterial community structure of the rhizosphere and bermudagrass roots. They also provide a foundation for understanding how the bermudagrass rhizosphere and root microorganisms respond to endophyte inoculation.

Traffic resistance of turfgrasses is an essential indicator of urban recreational and sports turf quality (TQ). In our study, four turfgrass species were investigated for their wear resistance. A self-made traffic simulator was used to determine the wear resistance of the study turf area in a 2-year field trial (2019–20). The experimental plots were established using a randomized block design with three replicates. The morphological characteristics, soil physical properties, and physiological indices of the grasses were analyzed. Using the acquired quantitative data, we set the turf cover index (TCI), the turf quality index (TQI), and the shoot density index (SDI) as the wear tolerance index, and assessed the correlations among these morphological characteristics, soil physical properties, physiological indices, and wear tolerance. ‘Lanyin III’ zoysiagrass and ‘Tifgreen’ hybrid bermudagrass provided relatively greater wear tolerance, followed by ‘Qingdao’ zoysiagrass and common bermudagrass after 12 weeks of traffic exposure in 2019 and 2020. Traffic changes the soil physical properties and affects the physiological metabolism of turfgrasses. Leaf morphology characteristics and the mechanical strength of these grasses were related significantly to TCI, TQI, and SDI, and most physiological responses and soil properties correlated significantly with TCI and TQI. Our findings of the correlations among physiological responses, soil properties, leaf morphology, and wear tolerance will allow grass breeders to evaluate their breeding procedures more efficiently.

Bermudagrass (Cynodon dactylon (L.) Pers.) is an extensively utilized turf grass for football fields and golf courses. Traffic stress is one of the most important stresses affecting the life of turf, which leads to a decrease in turf quality and changes in the soil microbial community structure. The structural change in soil bacterial community is an important reference for turf growth, maintenance, and restoration. Tifgreen bermudagrass turf and Common bermudagrass turf were applied with traffic treatment by a traffic simulator with moderate intensity to explore soil bacterial community structural changes in turf under traffic stress. The environmental factors including turf quality indicators and soil properties were measured, and the association of the soil bacterial community diversity with the environment factors was analyzed. As a result, traffic treatments significantly changed the soil properties and bacterial community composition in two bermudagrass species at the phylum and genus level. Actinobacteria, Chloroflexi, and Verrucomicrobia showed significantly high abundance in turf soils under traffic stress. The soil bacterial ACE, Chaol, and Shannon indexes of two bermudagrass species under traffic stress were significantly lower than non-traffic stress. The bacterial community structure was highly correlated with some turf quality indicators and soil properties under traffic stress. Our results illustrate that compared to Common bermudagrass, Tifgreen bermudagrass had better turf quality under traffic stress and less changes in its bacterial community structure, perhaps Tifgreen bermudagrass is a better choice of grass for sports turf as opposed to Common bermudagrass.

Soil nitrogen transformation has been the subject of growing attention in many semi-arid grassland ecosystems. In our study, we employed an intact soil core in situ incubation technique and measured seasonal changes in soil net nitrogen mineralization and nitrification rates. The measurements were taken from the upper 0-10 cm soil layer of a permanent grassland during a growing season in a 8.5-year field experiment on the Loess Plateau, China that had four grazing intensities (0, 2.7, 5.3 and 8.7 sheep ha). Our results demonstrate marked seasonal variations in inorganic nitrogen pools, net nitrogen mineralization and net nitrification. The rates of mineralization and nitrification were highest in August and lowest in September. No consistent differences in monthly net nitrogen mineralization and monthly nitrification rates were observed among the different grazing intensities. Sheep grazing stimulated nitrogen transformation, and the most stimulation occurred at a heavy grazing intensity of 8.7 sheep ha. The mean soil net nitrification rate was positively correlated with the soil C/N ratio and pH. The mean N mineralization rate was negatively correlated with soil organic carbon, but was positively correlated with the soil C/N ratio. Our study demonstrated net nitrogen mineralization and nitrification rates were strongly linked to grazing intensity, soil temperature and moisture content. [ABSTRACT FROM AUTHOR]