Soil pH is expressed by pH value. PH < 5.0 is strongly acidic, pH 5.0 ~ 6.5 is acidic, pH 6.5 ~ 7.5 is neutral, pH 7.5 ~ 8.5 is alkaline, and pH > 8.5 is strongly alkaline.
Determination of soil pH value: take a small amount of culture soil, put it in a glass, add water according to the ratio of soil: water = 1: 2, fully stir, dip the clear liquid with litmus test paper or pan-pH test paper, and know its pH value according to the color change of test paper.
Adjustment of soil pH value: When the acidity is too high, some lime powder can be added to the culture soil or the proportion of plant ash (rice bran ash is also acceptable) can be increased. When the alkalinity is too high, an appropriate amount of aluminum sulfate (alum), ferrous sulfate (green alum) or sulfur powder can be added. Ammonium sulfate can also reduce soil alkalinity and increase soil acidity when applying nitrogen fertilizer. Shui Pi can also neutralize the alkaline basin soil, soak the apple peel and core in cold water, and often water with this water, which can gradually reduce the alkalinity of the basin soil.