Does magnesium sulfate heptahydrate affect soil pH

       Magnesium sulfate heptahydrate (MgSO ₄· 7H ₂ O) is a commonly used agricultural fertilizer that contains two intermediate elements, magnesium and sulfur, which can provide nutrients for crops and have a certain impact on soil acidity and alkalinity. The following is a detailed analysis of the impact of magnesium sulfate heptahydrate on soil acidity and alkalinity:
       1、 Properties and functions of magnesium sulfate heptahydrate
       Magnesium sulfate heptahydrate is a compound containing magnesium and sulfate ions. When dissolved in water, it releases magnesium ions (Mg ² ⁺) and sulfate ions (SO ² ⁻). Magnesium ions are an important intermediate element for plant growth, which can promote photosynthesis and protein synthesis. Sulfate ions have a certain degree of acidity, but their acidity is relatively weak.
       2、 The impact on soil acidity and alkalinity
       Acidic soil:
       In acidic soil, the application of magnesium sulfate heptahydrate can neutralize some acidity and adjust the pH of the soil towards neutrality. This is because magnesium ions can replace hydrogen ions (H ⁺) in the soil, reducing the acidity of the soil.
       However, if the soil acidity is very strong (such as pH below 4.5), the neutralization effect of magnesium sulfate heptahydrate may be limited and needs to be used in conjunction with other amendments (such as lime).
       Neutral or alkaline soil:
       In neutral or alkaline soils, the acidic effect of magnesium sulfate heptahydrate is usually not significant. Its main function is to supplement magnesium element and promote plant growth.
       However, it should be noted that long-term and large-scale application of magnesium sulfate heptahydrate may lead to soil acidification, especially under conditions of poor drainage or insufficient irrigation.

       3、 Precautions in practical applications
       Soil testing: Before applying magnesium sulfate heptahydrate, it is recommended to conduct soil pH testing to determine the actual pH value of the soil. If the soil is already acidic, caution should be exercised when using magnesium sulfate heptahydrate to avoid further acidification.
       Reasonable fertilization: Based on soil testing results and crop needs, the application amount of magnesium sulfate heptahydrate should be reasonably controlled. It is generally recommended to apply 10-15 kilograms per acre.
       Combined with other amendments: In acidic soil, magnesium sulfate heptahydrate can be used in combination with alkaline amendments such as lime to achieve better improvement effects.
       4、 Research case
       Tengchong volcanic ash acidic soil: In the acidic soil of Tengchong tobacco growing area, the application of magnesium sulfate heptahydrate can significantly increase the magnesium content in the soil, but it will further aggravate soil acidification and decrease the pH value by 0.54-1.01.
       Fujian acid red soil: In the acid red soil of Fujian Province, the application of magnesium sulfate heptahydrate can increase the pH value of the soil by 0.18-0.29 and increase the content of exchangeable magnesium.
       The effect of magnesium sulfate heptahydrate on soil pH varies depending on the initial pH of the soil. In acidic soil, it can neutralize some acidity and adjust the soil acidity towards neutrality; In neutral or alkaline soils, its acidity is usually not significant. However, long-term and large-scale application of magnesium sulfate heptahydrate may lead to soil acidification, so it is necessary to use it reasonably according to the actual soil conditions and combine it with other amendments to achieve the desired effect.