Molecular Soil Biology 2024, Vol.15, No.1, 17-27 http://bioscipublisher.com/index.php/msb 22 beneficial effects over time (Souza et al., 2020; Martins et al., 2023). Moreover, the use of computational methods such as machine learning can optimize the selection and combination of microbial species in SynComs, enhancing their effectiveness in promoting plant health and soil resilience. By leveraging these innovative strategies, SynComs offer a sustainable solution for the restoration and maintenance of soil health in saline-alkali environments. 4 Integrative Approaches to SynCom Design and Application 4.1 Selection of microbial strains and engineering for specific soil health functions The selection of microbial strains for SynComs in saline-alkali environments is crucial for enhancing soil health and plant growth. Studies have shown that certain bacterial and fungal communities exhibit higher tolerance and resilience to saline-alkali stress, making them ideal candidates for SynComs. For instance, keystone bacteria and fungi identified in various saline-alkali soils, such as those in Inner Mongolia, demonstrate potential adaptability and benefits in restoring soil health (Zhang et al., 2021). Additionally, the use of microbial inoculums, such as those involving T. ambiguum Bieb., has shown significant improvements in soil fertility and reduction in salinity and alkalinity (Li et al., 2021). Engineering these microbial strains to enhance their specific functions, such as nitrogen cycling and salt tolerance, can further improve their efficacy in SynComs. 4.2 Optimization of SynCom composition and diversity for saline-alkali environments Optimizing the composition and diversity of SynComs is essential for their success in saline-alkali environments. Research indicates that a diverse microbial community can better withstand environmental stresses and improve soil health. For example, the combination of organic amendments, such as farm manure and desulfurization gypsum, has been shown to increase bacterial community richness and enzyme activities, thereby enhancing soil quality. Similarly, the addition of vermicompost and humic acid fertilizer has been found to improve soil aggregate stability and microstructure, leading to better salt leaching and nitrogen retention (Liu et al., 2020). By carefully selecting and combining microbial strains that complement each other, SynComs can be tailored to address the specific challenges of saline-alkali soils (Qin et al., 2016). 4.3 Integration of SynComs with other soil management practices (e.g., organic amendments, crop rotation) Integrating SynComs with other soil management practices can amplify their benefits and contribute to sustainable soil health restoration. Organic amendments, such as farm manure and straw, have been shown to significantly improve microbial diversity and soil organic carbon content, which are critical for soil health (Liu et al., 2023) Additionally, practices like crop rotation and the use of cover crops can enhance the effectiveness of SynComs by providing a continuous supply of organic matter and promoting beneficial microbial interactions (Qin et al., 2016). For instance, the combination of microbial inoculums with terraced landscape design has proven effective in reducing salinity and alkalinity while improving soil fertility in oil-polluted areas (Li et al., 2021). By integrating SynComs with these complementary practices, a holistic approach to soil health restoration in saline-alkali environments can be achieved. 5 Field Applications and Performance Evaluation 5.1 Overview of methodologies for field application of SynComs The application of engineered synthetic microbial communities (SynComs) in saline-alkali soil restoration involves several methodologies aimed at enhancing soil health and crop productivity. One common approach is the amendment of soils with organic and inorganic materials that support microbial activity and diversity. For instance, the use of farm manure, desulfurization gypsum, and sandy soil has been shown to significantly improve soil pH and enzyme activities, thereby fostering a conducive environment for microbial communities (Shi et al., 2019). Additionally, the incorporation of vermicompost and humic acid fertilizers has been found to improve soil aggregate stability and microstructure (Liu et al., 2020). 5.2 Key field trials and case studies of SynComs in saline-alkali soil restoration Several field trials have demonstrated the efficacy of SynComs in restoring saline-alkali soils. A notable study conducted over seven years revealed that amendments with farm manure, desulfurization gypsum, and a mixture
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