1. The term pH is used to indicate the level of acidity or alkalinity of a soil. 

2. The range of pH values of a good soil live from 5.5 to 7.5. 

3. Below pH 7 the soils are termed as acidic and above pH 7 alkaline.

Negative impacts of low pH value :

1. The concentration of soluble metals especially aluminium and manganese may be toxic.

2. Calcium may be deficient. 

3. Soil organisms responsible to transform N, S and P to plant available forms may be reduced. 

4. Symbiotic nitrogen fixation in legume crops is greatly impaired. 

5. Soils will be having low organic matter. 

6. The availability of mineral elements to plants may be effected.

Negative impacts of high pH value :

1. If the pH is beyond 7, nutrient absorption and microbial activity will be affected which can be poisonous to plants. 

2. PH extremes are unhealthy for most plants because they close or open membranes of plant cells too much.

3. This affects plant structure and their ability to uptake nutrients. 

4. pH extremes make minerals and nutrients either too available or not available enough.