Page 78 - Soil Degradation, Conservation and Remediation

64 2 Physical Deterioration of Soil

Fig. 2.4 Desertifi cation
scheme

Overgrazing is the major cause of desertification worldwide. Cultivation of marginal
lands, lands on which there is a high risk of crop failure and a very low economic

return, increases the risk of desertification in many areas. Destruction of vegetation
in arid regions for fuelwood and burning of vegetation are responsible for denudation
in many places. Incorrect irrigation practices in arid areas can cause salinization,
which can prevent plant growth. Organic matter of soil is depleted due to reduced
biomass production and enhanced decomposition. Soil structure is destroyed and
soil particles are removed by water and wind erosion. Continuous erosion exposes

the subsoil which lacks the capacity of supporting sufficient vegetation. Wind and
water erosion leads to development of gullies and sand dunes across the defl ated
land surface. A hypothetical desertification scheme is presented in Fig. 2.4 .

Study Questions

1. What do you mean by physical deterioration of soil? What are the types and

processes of physical deterioration of soil? Distinguish among surface sealing,
crusting, hardsetting, compression, consolidation, and compaction. Soil com-
paction is a problem associated with mechanized agriculture – Discuss.

2. What are the differences among flooding, submergence, water saturation, and
waterlogging? How does human activity aggravate waterlogging? What are the
consequences of waterlogging of soil?

3. What is groundwater? How does interaction take place between groundwater
and surface water? What do you mean by recharge and discharge of groundwa-
ter? What are the sources of groundwater recharge? What are the consequences
of lowering of groundwater table?

4. What are the characteristics of peat soil? Discuss subsidence of peat soils due to

their draining and reclamation.
5. What is desertification? Distinguish between denudation and desertifi cation.

Explain the processes of desertification.