Molecular Soil Biology 2025, Vol.16, No.5, 255-264 http://bioscipublisher.com/index.php/msb 260 urea, etc.) to each 15-year-old declining bayberry tree and regulated pH through circular furrow application (Ren et al., 2023). Lime application reduces aluminium toxicity by neutralizing acidity and is widely used in orchards (Chen et al., 2022). 7.3 Observed outcomes In terms of tree body and fruit: After biochar treatment, the vitality of the bayberry tree was significantly enhanced, the leaves and spring shoots grew better, and the sugar and vitamin C contents in the fruit also increased (Ren et al., 2023). In terms of soil properties: Biochar can increase soil pH, organic matter and available nitrogen, phosphorus and potassium. It can also increase exchangeable calcium and magnesium and reduce harmful aluminum ions (Chen et al., 2022). Microbial aspect: Biochar promotes the reproduction of beneficial microorganisms such as Mycobacterium and Fusarium, increases diversity, and improves the rhizosphere metabolic environment (Hong et al., 2023). In terms of metabolites: Under the action of biochar, beneficial metabolites such as antioxidants and amino acids in the rhizosphere soil increase, helping plants to be healthier (Ren et al., 2023. 7.4 Lessons learned: Scalability, farmer adoption, challenges in long-term maintenance In terms of promotion and application: Lime and biochar for pH adjustment are simple to operate and have obvious effects, making them suitable for promotion in large-scale acidic red soil orchards. Some regions have adopted this as a routine measure (Chen et al., 2022). In terms of long-term challenges: Soil acidification is a long-term accumulated problem that requires continuous monitoring and regular supplementation of conditioners. Biochar is relatively expensive, so policy and technical support are needed to alleviate the burden on farmers. In terms of comprehensive management: If measures such as organic fertilizers and associated plants are combined for use, soil health can be better improved and orchards can be made more sustainable (Ren et al., 2023; Hong et al., 2023). 8 Knowledge Gaps and Future Directions 8.1 Thresholds of pH tolerance at different growth stages At present, there are not many studies on the tolerance of bayberries to soil pH at different growth stages (seedling, flowering, fruiting, senescence). Existing results have shown that when the pH is lower than 4.5, the growth of bayberries will be affected, with a decline in yield and quality, and they are also prone to decay diseases. However, at different stages, the most suitable and critical pH values still lack detailed staged experimental data (Ren et al., 2021; Li et al., 2022). In the future, phased field and greenhouse experiments need to be conducted to draw the pH response curves for each period and determine the thresholds. Only in this way can a basis be provided for precise regulation. 8.2 Molecular basis of pH-regulated nutrient uptake and fruit metabolism Some studies have now shown that soil pH can affect rhizosphere microorganisms, nutrient utilization rate and fruit metabolite composition (Ren et al., 2021; 2023) (Figure 2). However, the molecular regulatory mechanism of pH changes in bayberries remains unclear. Compared with acid-tolerant crops such as blueberries, studies have found that pH stress can cause changes in the expression of hundreds to thousands of genes, involving nutrient transport, cell wall metabolism and signal transduction (Paya-Milans et al., 2017). Transcriptome and metabolome analyses of bayberry during fruit development and ripening have provided some clues for pH regulation of quality formation (Sun et al., 2024), but the key genes, pathways and their relationship with the rhizosphere environment still require more in-depth research.
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