Previous Year Question

All four practices help control soil erosion caused by water or wind.

1. Crop rotation—Appropriate

Crop rotation involves growing different crops in a planned sequence on the same field. Its benefits include:

• crops with different root depths utilise different soil layers;

• leguminous crops fix nitrogen with the help of Rhizobium bacteria;

• soil organic matter and structure improve;

• longer vegetation cover reduces the direct impact of raindrops;

• pest, disease and weed cycles are interrupted; and

• surface runoff and the movement of soil particles are reduced.

Crop rotation therefore maintains soil fertility while also reducing erosion.

2. Sand fences—Appropriate

Sand fences are low barriers constructed from wooden slats, brushwood, reeds, mesh or other porous materials. They are generally placed across the direction of the prevailing wind.

By reducing wind velocity near the ground, they cause wind-blown sand to accumulate around the fence. This:

• controls the movement of sand dunes;

• reduces the deposition of sand on agricultural fields, roads and canals; and

• creates a relatively stable surface for vegetation establishment.

They are useful in arid, semi-arid and sandy coastal areas. For long-term stabilisation, sand fences are generally supplemented with grasses and shrubs.

3. Terracing—Appropriate

Terracing converts a hill slope into a series of level or nearly level steps. It:

• reduces slope length and steepness;

• slows the velocity of surface runoff;

• increases water infiltration;

• traps transported soil particles; and

• controls sheet, rill and gully erosion.

It is particularly useful in the Himalayas and other hilly regions. Proper drainage and regular maintenance are essential for terrace stability.

4. Wind breaks—Appropriate

Wind breaks are rows of trees and shrubs planted along field boundaries, approximately perpendicular to the prevailing wind. They are also known as shelterbelts.

They:

• reduce wind speed near the soil surface;

• prevent the removal of fertile topsoil;

• protect crops from wind damage;

• reduce evaporation and moisture loss; and

• help stabilise sand dunes in desert regions.

Important examination point

Option (c) includes crop rotation, terracing and wind breaks but excludes sand fences. Sand fencing is also a recognised method of controlling wind erosion and sand movement. Therefore, all four practices are appropriate.