The protection of soil from erosion. Reclamation of lands.

A lithosphere (Ancient Greek: λίθος [ lithos ] for "rocky", and σφαίρα [ sphaira ] for "sphere") is the rigid,^[1] outermost shell of a terrestrial-type planet or natural satellite that is defined by its rigid mechanical properties. On Earth, it is composed of the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater. The outermost shell of a rocky planet, the crust, is defined on the basis of its chemistry and mineralogy.

Earth's lithosphere includes the crust and the uppermost mantle, which constitute the hard and rigid outer layer of the Earth. The lithosphere is subdivided into tectonic plates. The uppermost part of the lithosphere that chemically reacts to the atmosphere, hydrosphere and biosphere through the soil forming process is called the pedosphere. The lithosphere is underlain by the asthenosphere which is the weaker, hotter, and deeper part of the upper mantle. The boundary between the lithosphere and the underlying asthenosphere is known as the Lithosphere-Asthenosphere boundary and is defined by a difference in response to stress: the lithosphere remains rigid for very long periods of geologic time in which it deforms elastically and through brittle failure, while the asthenosphere deforms viscously and accommodates strain through plastic deformation. The study of past and current formations of landscapes is calledgeomorphology.

This subdivision of the biosphere plays two vital roles in metabolism.

First, it is the only source of most mineral metabolites for all the organisms, terrestrial as well as aquatic; and second, it forms the bulk component of soil (pedosphere), required particularly by the terrestrial plants.

Soil is formed from disintegration of rocks by the action of running water and weathering. Living organisms also contribute to soil formation. Their decay produces organic fractions of soil, collectively called humus. Humus mixed with sand and clay constitutes the soil. Soil is affected by climate (temperature and rainfall), vegetation and human activities.

1. Soil Degradation:

It has been reported from many parts of the country that agricultural intensification, faulty irrigation techniques, deforestation and excessive use of pesticides and herbicides have lead to widespread soil degradation. According to one estimate, about 300 million ha of land is now highly degraded and about 1.2 billion ha or 10% of the earth’s vegetated surface is described as moderately degraded. In India, the worst examples of soil degradation have been observed in Gujarat, Rajasthan and Bihar.

The desertification of soil in Rajasthan is attributed to deforestation and cattle grazing. Agricultural land is also highly susceptible to degradation in arid and semiarid regions. Both overgrazing and excessive cultivation expose the soil directly to erosion by the wind.

In the process of desertization, arid and semiarid land that has supported subsistence or nomadic agriculture gives way to desert. The process may be slowed by irrigating the land, which gives a temporary remission but lowers the water table, and salts accumulate in the topsoil (salinization). Once salts have started to accumulate, the process of salinization tends to spread and leads to sterile white salt deserts. This has been observed in many areas of India and Pakistan.

However, the degradation of soil by intensive agriculture can be prevented or slowed by:

(a) Returning the land to grazed pasture or rangeland;

(b) Use of farmyard manure, crop residues and animal wastes and

(c) Alternating years under cultivation with years of fallow.

2. Soil Erosion:

Soil erosion is a process in which useful land is washed off through excessive rains and soil runoff. The Rio conference, 1992 also adopted Agenda 21 for soil conservation and recommended measures, now coordinated by the United Nations Commission on Sustainable Development, to prevent soil erosion, in particular minimizing soil runoff and sedimentation. The main factors or forces responsible for removal or displacement of soil from one place to another are water and wind.