(2) Soil pH

     What is soil pH?

                                  Soil pH is the acidity and alkalinity of the soil. pH more than 7 is alkalinity. pH lower than 7 is acidity. 7 is natural which is pure water.

                                  Soil pH is one of the most important soil properties that affect the availability of nutrients. Nutrients are essential for the healthy growth of plants. They can be divided into three categories as macronutrients and micronutrients. Micronutrients are B, Cu, Fe, Cl, Mn, Mo and Zn. Macronutrients can be also divided into two categories as primary nutrients and secondary nutrients. Primary nutrients are N, P, and K. Secondary nutrients are Ca, Mg and S.

                                       Secondary nutrients and micronutrients are less available at lower acidity. Macronutrients are less available for higher acidity. Therefore pH affects the growth of plants by the availability of nutrients at a certain pH. Some minerals are also toxic by increasing concentration in soil. Al and Mn are more available at highly acidic soil that is toxic to soils.

2.2   Factors Affecting Soil pH

1) Climate

2) Parent material

When parent material is acid rock, pH is acidity. When parent material is basic, pH is alkalinity.

3) Rainfall

             Soils formed under high rainfall conditions are more acidic than those formed under arid (dry) conditions.

4) Fertilizers

Fertilizers that are consist of ammonia and urea, develop the acidity in the soil. The decomposition of organic matter has also increased the acidity of the soil.

2.3 Increasing the Soil pH

Lime can be added to the soil to make it less acidic and also supplies calcium and magnesium for plants to use. Different soils will require a different amount of lime to adjust the soil pH value. The texture of the soil, organic matter content and the plants to be grown are all factors to consider in adjusting the pH value. For example, soils low in clay require less lime than soils high in clay to make the same pH change.

– Lime also raises the pH to the desired range of 6.0 to 6.5. In this pH range, nutrients are more readily available to plants, and microbial populations in the soil increase

2.3.1  Function of limes

1)    Toxicities include Al is reduced.

2)    Soil physical conditions are improved.

3)    Microbial activities are stimulated.

4)     The availability of essential nutrients is improved.

5)    Ca and Mg are supplied for plants.