Question

Give reasons for the following.

Black soil forms crack when it dries up.

Answer 1

1. High Content of Montmorillonite Clay: Black soil (also known as Regur soil) is extremely rich in fine clay particles, notably montmorillonite. This clay mineral has an expanding crystal lattice structure that is highly sensitive to moisture levels.
2. High Moisture Absorption and Swelling: When it rains, this clay absorbs a large amount of water, causing the soil to swell and become extremely sticky. During this moist period, the earth expands to its full capacity, closing any open spaces.
3. Evaporation and Shrinkage: During the dry summer season, the water held within the clay evaporates quickly. As moisture evaporates, soil particles squeeze firmly together and shrink dramatically in volume.
4. Tension and Cracking: Because the shrinking soil is closely linked, high physical tension causes the earth to pull apart. This leads to the creation of deep, wide fissures across the landscape.
5. The “Self-Ploughing” Benefit: While these cracks appear destructive, they actually perform an important natural role. Granular topsoil falls into these deep cracks, allowing the soil to rotate its layers and absorb essential oxygen and nitrogen deep into the earth, a natural activity known as self-ploughing.