What happens when rain falls on soil without vegetational cover?
a. Rain water percolates into soil efficiently
b. Rain water causes loss of surface soil
c. Rain water leads to fertility of soil
d. Does not cause any changes in the soil

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Hint: Rainfall erases levels of soil organic matter, and contributes to the breakdown of soil structure. This creates a less advantageous plant growing environment.

Complete answer:
> Option A is incorrect. Rain water marks a major source of groundwater recharge. It is percolated into the shallow and deep aquifer by itself through uncovered surfaces of soil and fissures. Percolation tank (an alternative to groundwater recharge) is an entirely artificial surface water body, drenching a highly permeable soil in its reservoir, making the surface runoff percolate and recharge the groundwater storage.

> Option B is correct. Trees act as a natural absorber, during heavy rainfall. They prevent soil erosion, reducing the sediments from entering rivers, and increasing the absorption of water into the soil. But when the soil has no vegetational cover, rainwater carries away the soil, often with the highest biological activity and the highest amount of organic soil matter.

> Option C is incorrect. Low crop yield was due to poor soil moisture and soil fertility inherent in it. The falling rain improves soil fertility over a short period. Rainwater harvesting in situ possesses the potential to increase the availability of moisture to crops during dry periods and increase crop growth.

> Option D is incorrect. Soil is also highly impacted by rainfall. If it is too wet or too dry, the nutrients in the soil may run off and not make it to the roots of the plants, resulting in poor growth and general health. Moreover, overwatering or too much rain can also lead to soil growth of bacteria, fungus, and mold.

Hence, The correct answer is option (B).

Note: Plant roots hold particles from the soil and prevent their loss. Therefore, vegetation prevents the erosion of the soil. Due to the loss of the upper layer of soil caused by heavy wind or flowing water, soil erosion occurs when vegetation is lost and the soil is kept barren after harvest.