Alkalinity in soil can occur due to the following reasons:
1. Alkaline Lithology: Soil formed from alkaline rocks exhibits an alkaline reaction. For example, soils formed from limestone or dolomite have high lime content. This type of soil is alkaline in nature. The high lime (CaCO₃) content in these rocks causes the soil to become alkaline.
2. Marine Inundation: When soil in an area is repeatedly inundated by salty water from ocean tides, it becomes rich in sodium. As a result, the soil may become alkaline.
3. Climatic Factors: In arid regions, due to low rainfall, the absorption of calcium and magnesium is reduced. This leads to the accumulation of alkaline substances in the upper layer of the soil, causing it to become alkaline.
4. Use of Sodium-Rich Irrigation Water: Continuous use of poor-quality water, particularly water with high sodium content, can lead to soil alkalinity. Sodium in the water dissolves and disintegrates soil organic matter, increasing the soil’s alkalinity.
5. Improper Drainage: In the absence of proper drainage, waterlogging in the land causes water to evaporate, which increases the sodium content in the topsoil and results in soil alkalinity.