Tree Genetics and Molecular Breeding 2025, Vol.15, No.4, 138-146 http://genbreedpublisher.com/index.php/tgmb 140 high, it is easier to maintain a low pH, which is also conducive to root growth (Costello et al., 2019; Zhou et al., 2022). In addition, the amount and duration of effect of acid-adjusting agents (such as sulfur, peat, sulfur-oxidizing bacteria, etc.) also depend on the buffering capacity of the soil. 3 Effects of Soil pH on Growth, Yield, and Fruit Quality 3.1 pH effects on vegetative growth and root development If the pH of the soil rises, blueberries are likely to grow poorly. For instance, the plant becomes shorter, the main trunk becomes thinner, the number of branches decreases, and the dry weight of leaves, stems and roots all drops. The greenness of leaves (SPAD value), chlorophyll content and photosynthetic efficiency will also decrease (Jiang et al., 2019). In alkaline soil, the roots grow poorly, the types of surrounding microorganisms decrease, and the enzyme activity in the soil also declines. All these will affect the nutrient absorption and normal growth of blueberries (Zhou et al., 2022; Egorova et al., 2024). In addition, the roots of blueberries have no root hairs. They absorb nutrients through the mycorrhizal system formed together with fungi, and this system works best in acidic soil. 3.2 Yield response under various pH conditions The yield of blueberries is highly influenced by soil pH. Research has found that if the pH is raised from 4.5 to 6.5, the yield of blueberries will drop by more than 60%. The fruit ripens later and the number of flower buds and flowers will also decrease (Egorova et al., 2024). The adaptability of different blueberry varieties to alkalinity varies, but generally speaking, the yield is the best when the pH is below 5.5 (Yang et al., 2022a). Adjusting soil pH with organic materials such as corn stalks and pine needles can also significantly increase the yield per blueberry plant and the weight of individual fruits (Kim et al., 2017). 3.3 Impacts on fruit set, berry size, anthocyanin content, and flavor profile In an environment with a high pH value, blueberries bear less fruit, the fruit becomes smaller, the sweetness decreases, the sourness intensifies, and the overall taste deteriorates (Egorova et al., 2024). When the soil pH is appropriate, the contents of anthocyanins, soluble solids and vitamin C in the fruits will be higher and the quality will be better. Under high pH conditions, the taste of the fruit will become milder, the sugar-acid ratio will decrease, affecting the appearance and commercial value (Jiang et al., 2019; Yu et al., 2020). 3.4 Role of pH in nutrient availability and physiological disorders If the soil pH is too high, it will also make it difficult for trace elements such as iron, manganese and zinc to be absorbed by plants, and it is easy to have nutrient deficiency problems, such as yellowing of leaves and withering of edges (Jiang et al., 2019). When the pH is high, most of the nitrogen in the soil turns into nitrate nitrogen. However, blueberries are not very fond of this form of nitrogen and it may also lead to iron precipitation, making the iron deficiency problem more severe (Smith and Harris, 2017). However, it should not be too sour either. If the pH is too low, it will cause excessive ions such as aluminium and manganese, generating toxicity, which is not good for the roots and fruits of blueberries (González-Villagra et al., 2021; Ngoc et al., 2022). 4 Soil pH Regulation Strategies in Blueberry Cultivation 4.1 Use of acidifying amendments Common acid-adjusting materials include sulfur powder, sulfuric acid, phosphogypsum and urea phosphate. Studies have shown that sulfur powder can rapidly lower the pH of the soil, while urea phosphate not only makes the soil acidic but also enhances the activity of soil enzymes (Ochmian et al., 2020). In addition, by adjusting the types of nitrogen fertilizers, such as increasing the proportion of ammonium nitrogen, the soil can also become more suitable for blueberry growth (Tamir et al., 2021; Tamir et al., 2022). 4.2 Organic acid applications and pH-buffering mulches Adding some organic materials, such as pine bark, humus or vinegar residue, can not only improve soil structure, but also slowly release organic acids to help maintain soil acidity, while increasing organic matter. Some pine needles or acidic humus can also be spread on the ground. These mulch can act as a buffer and slow down the change of pH, which is very helpful for the blueberry root system and the microorganisms in the soil (He et al.,
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