How are soil acidity and alkalinity related to soil fertility?
(UPSC geography optional paper 1 2019, 15 Marks)
Answer:
Soil acidity and alkalinity, both are related to fertility and extreme acidity and alkalinity are bad for soil fertility.
Acidic soil
The soil will be called acidic if the pH value is less than 7 and extremely acidic if the soil has a pH value less than 5.5.Reasons for Soil Acidity:
There are mainly four reasons for soil acidity:
- Heavy Rainfall leached many key nutrients such as potassium, magnesium, calcium from soil and it makes the soil acidic.
- Excess use of water in farming or waterlogging in field
- Excess use of chemical fertilizer comprises nitrogen.
- Organic manure such as forest Leafs
Region of Acidic Soil:
It is found generally in:
- High rainfall areas
- Coastal areas
- Forest or Hilly areas
How soil acidity is related to soil fertility?
- In acidic soil, nutrients are absorbed by plant roots very fast and vegetation is not able to consume them fastly and the plant dies.
- Soil having a pH value between 7 and 5.5 is suitable for many crops such as rice, wheat, barley, sugarcane, cotton, etc.
- Extreme acidic soil is not suitable for the majority of crops.
Agriculture Lime is used to reduce the acidity in the soil.
Alkaline Soil:
A soil having more than 7 pH values will be called alkaline and highly alkaline if having more than 8 pH values.Reasons for soil alkalinity:
- Through capillary action, salt comes up at the surface in areas where evaporation is greater than precipitation.
- Soil gets alkaline after the evaporation of waterlogged areas. Over irrigation or poor drainage is responsible for waterlogging.
- Calcium-rich Parent Material weathering
- Over liming of acidic soil
Region of Alkaline Soil:
- Alkaline soil is found in the following region:
- Arid and Semi-Arid region
- Evaporated areas after waterlogging
How soil acidity is related to soil fertility?
- Alkaline soil prevents plant roots to absorb the nutrients effectively as nutrients do not get dissolved easily in alkaline soil and thus plant growth gets affected due to deficiency in nutrients.
For making alkaline soil fertile or lowering the pH values of soil sulfur, ferrous sulfate, and aluminum sulfate are used.
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