Soil pH measures acidity and alkalinity, with optimal levels for most plants between 5.5 and 7.0. Factors influencing pH include rainfall, fertilizers, and minerals, affecting nutrient availability and plant growth. Adjustments can be made to soil pH by adding lime to increase acidity or using acidifying agents to lower alkalinity.

1. pH value of soil
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Name: Shaikh Ashraful Alam
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2. Soil PH: What it Means
o Soil pH is a measure of the acidity and alkalinity in soils.
o The optimal pH range for most plants is between 5.5 and 7.0.
Range of PH
o The pH scale goes from 0 to 14 with
pH 7 as the neutral point.
o From pH 7 to 0 the soil is
increasingly more acidic and from
pH 7 to 14 the soil is increasingly
more alkaline or basic.
o Any soil above pH 10 and below pH
3 may be said sterile.

3. Sources of acidity
o Rainfall
o Fertilizer use
o Plant root activity
o Acid rain
o Mine spoil
Sources of alkalinity
o Alkaline soils have a high saturation of base cations (K+, Ca2+,
Mg2+ and Na+).
o Alkaline soils are characterized by the presence of carbonates.
o Soil in areas with limestone near the surface are alkaline from the
calcium carbonate in limestone constantly mixing with the soil.

4. Measuring Soil pH
o The most accurate method of determining soil pH is by a pH meter
o Using certain indicators or dyes.
pH Affects Nutrients, Minerals and Growth
o The effect of soil pH is great on the solubility of minerals or nutrients.
o Phosphorus is never readily soluble in the soil but is most available in soil with
a pH range centered around 6.5.
o Extremely and strongly acid soils (pH 4.0-5.0) can have high concentrations of
soluble aluminum, iron and manganese which may be toxic to the growth of
some plants.
o A pH range of approximately 6 to 7 promotes the most ready availability of
plant nutrients.

5. Changes in Soil pH
Increasing pH of acidic soil:
o Lime is usually added to acid soils to increase soil pH.
o The addition of lime not only replaces hydrogen ions and raises soil pH.
o Eliminating most major problems associated with acid soils but it also provides two
nutrients, calcium and magnesium to the soil. Lime also makes phosphorus that is
added to the soil more available for plant growth .
Decreasing pH of alkaline soil:
o The pH of an alkaline soil can be reduced by adding acidifying agents or organic
materials.
o Acidifying fertilizers, such as those containing ammonium, can help to reduce the
pH of a soil.
o Add elemental sulfur (90 or 99% sulfur material) annually at a rate of 6 to 10
pounds per 1000 square feet of area.