Question

How can you raise the pH of acidic soil?

Answer 1

Hint: Acidity or basicity can be specified using a pH scale. The pH scale denotes the potential or the power of hydrogen. Acidic solutions have a lower pH while basic solutions or alkaline solutions have a higher pH value.

Complete answer:
The measure of the acidity or alkalinity of soil is known as soil pH. Quantitative and qualitative analyses of the characteristics of soil can be done using soil pH.
The pH of the soil is measured by making a slurry of soil, that is mixing soil in water. Usually, the pH of the soil has a range between 3 and 10. The ideal pH range for most plants is between 5.5 and 7.5.
Soils that have a pH value of less than 7 are known as acid soils and the soil is considered to be ultra-acidic soils if its pH value is less than 3.5.
Soils that have a pH value of more than 7 are known as alkaline soils and soil is considered to be strongly alkaline if its pH value is more than 9.
Ultra-acidic soils and strongly alkaline soils occur rarely.
The pH of the soil is dependent on various factors.
Some of the sources of acidity in the soil are
- Rainfall
- Acid Rain
- Fertilizer
- Plant Growth
- Root Respiration
- Oxidative Weathering
Some of the sources of alkalinity in the soil are
- Weathering of carbonate, silicate, or aluminosilicate minerals containing $N{{a}^{+}},\text{ C}{{\text{a}}^{2+}},\text{ M}{{\text{g}}^{2+}}\text{ and }{{\text{K}}^{+}}$
- Addition of carbonate, silicate, or aluminosilicate minerals
- Addition of water that has dissolved bicarbonates
Now to raise the pH of acidic soil, we have to increase the alkalinity of the soil.
This can be done by adding limestone into the soil. Finely ground agricultural lime is usually used. This process is called liming. Different types of soil require a different amount of limestone.
Wood ash, basic slag or calcium silicate, magnesium oxide, oyster shells or industrial calcium oxide, or burnt lime can also be used to raise soil pH through acid-base reactions.

Note:
Acid soils pose various stresses to plant growth like Al, H, or Mn toxicity and Ca or Mg nutrient deficiency, hence the need to increase pH. The modification of the pH of soil requires repeat treatments and is often a slow process. To maximize effectiveness, a combination of treatments should be used.