Tree Genetics and Molecular Breeding 2025, Vol.15, No.4, 138-146 http://genbreedpublisher.com/index.php/tgmb 139 from 4.5 to 5.0 (Lee et al., 2021). In soil with a high content of organic matter, the pH value is best controlled between 4.0 and 5.0. In mineral soil, the ideal range is 5.0 to 5.5. If the pH exceeds 5.5, blueberries are prone to poor growth. For example, the leaves will turn yellow, the plants will not grow tall, and there will be fewer fruits (Figure 1) (Jiang et al., 2019; Zhou et al., 2022). Figure 1 Correlation analysis of soil and plant chemical properties and root metabolome (Adopted from Zhou et al., 2022) Image caption: The color gradient on the right represents Spearman’s correlation coefficients. The chemical properties and metabolites used have passed the partial Mantel tests. The thickness of the curve in the figure is proportional to the Mantel r statistic of the corresponding distance correlation, and the color of the curve indicates the statistical significance based on 9999 permutations (the legend at the bottom corresponds to p values) (Adopted from Zhou et al., 2022) 2.2 Root physiology and pH-related nutrient uptake The roots of blueberries are very sensitive to changes in pH. In an acidic environment, its roots activate a mechanism called H⁺-ATPase to pump H⁺ out, which is conducive to the absorption of trace elements such as Fe and Mn (Tamir et al., 2020; Tamir et al., 2021). However, if the pH is too high, this pump will not work well, the activity of the roots will decrease, the absorption of Fe and Mn will be poor, the leaves will be deficient in nutrients, and photosynthesis will also decline (Jiang et al., 2019; Yang et al., 2022b). One more important point is that blueberries prefer ammonium nitrogen (NH₄⁺). If the content of NH₄⁺ in the fertilizer is higher, it can help lower the pH near the roots and facilitate nutrient absorption 2.3 Common pH problems: alkalinity, acidification, and regional limitations Alkaline soil (pH>5.5) is a big problem for growing blueberries. This situation is common in lime soil or areas with a lot of alkaline fertilizers, which can easily lead to iron and manganese deficiency and slow plant growth (Jiang et al., 2019). However, the soil should not be too acidic. If the pH is lower than 4.0, especially in mineral soil, aluminum or manganese poisoning may occur. Because the soil pH varies from place to place, in order to grow blueberries well, sulfur, peat or acidic organic matter is usually added to adjust the soil pH (Costello et al., 2019; Novak et al., 2023). 2.4 Influence of soil type, texture, and buffering capacity Different soil types can also affect the effect of pH regulation. Soils like peat soil or sandy loam, where pH adjustment is relatively easy, changes rapidly and over a wide range, are more suitable for growing blueberries (Lee et al., 2021; Novak et al., 2023). However, loam silty soil, which has strong buffering capacity and changes pH very slowly, is not very suitable for blueberries (Ochmian et al., 2020). If the soil organic matter content is
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