Agronomic Soil Conservation measures -

Use of Vegetation: Crops and vegetables which cover the ground surface well and have extensive root system reduce soil erosion. Plant canopy protect the soil from the adverse effect of rainfall. The grasses and legumes produce dense sod which helps in reducing soil erosion. The vegetation provides organic matter to the soil. As a result, the fertility of soil increases and the physical condition of soil is improved. Following cropping systems help in controlling soil erosion -

Crop rotation: Crop rotation is planned sequence of cropping. Rotation of crop is an important method for checking erosion and maintaining productivity of soil. A good rotation should include densely planted small grain crops, spreading legume crop etc. which may check soil erosion.

Strip Cropping: It consists of growing erosion permitting crop (e.g. Jowar, Bajra, Maize etc.) in alternate strips with erosion checking close growing crops (e.g. grasses, pulses etc.). Strip cropping employs several good farming practices including crop rotation, contour cultivation, proper tillage, stubbles mulching, cover cropping etc. It is very effective and practical means for controlling soil erosion, specially for gently slopping land. It may be of different types as follows:

• Contour strip Cropping: Contour strip cropping is the growing of erosion permitting and erosion resisting crops alternately in strips across the slope and on the contour line. This practice is useful because it checks the fast flow of run-off water increases the infiltration of water in the soil and prevents soil erosion.

• Field Strip Cropping: Strips of crop are parallel to the general slope of the land.

• Wind Strip Cropping: Strips of crop are across the direction of wind regardless of contour.

• Buffer Strip Cropping: In this, the severally eroded portion of land is permanently kept under grass and contour strip cropping is practices in the rest of the area.

There is a special type of contour strip cropping in which care is taken to check soil erosion.

Cultivation of dense plant and grasses: Sod forming crop such as lucern (medicago sativa L), Egyptian Cloveror. Berseem (Trifolium alexandrinum), ground nut (Arachis hypogea L), Sannhemp (Crotolaria juncea), grass etc. cover the surface of the land and their roots bind the soil particles to form soil aggregates, thus preventing soil erosion.

Cultivation of proper crops: Cultivation of row crop in sloppy lands permits soil erosion. In this filed, the crops particularly cereals, fodder crop etc. should be broadcasted and the plants remain haphazardly in field. As a result, the movement of water gets obstacle and more water is absorbed in the soil, thus reducing soil erosion.Mixed and intercropping (Cowpea-Vigna catjang, with cotton – Gossipum Sp, maize – Zea mays with soyabean – Glycine max etc.) practice checks the soil erosion and avoids the risks of the crop failure.

The land should not be kept without crop: There is very scope of soil erosion if there are no crops on the land. The soil erosion decreases in different way of cropped land.

Afforestation: Afforestation means growing of forests where there were no forests before owing to lack of seed trees or due to adverse factors such as unstable soil, aridity or swampiness. Along with afforestation, reforestation should be undertaken which means replanting of forests at places where they have been destroyed by uncontrolled forest fires, excessive felling and lopping. Afforestation is the best means to check the soil erosion. Lutz and Chandler (1946) cited the following points in support of vegetational check erosion as follows:

• Infiltration of water is favoured due to high porosity of soil under vegetation. Percolation of water helps in preventing the soil moisture which accelerates further growth of the vegetation.

• Surface accumulation of organic matter increases the water holding capacity of the underground soil.

• Root system of vegetation holds the soil mechanically and provides stability of the underground soil.

• It gives the protection against wind. The forest vegetation shields the soil from direct effect of drought, snow and rain.

Mulching:  Mulches of different kinds such a leaves, straws, paper, stubbles, etc. minimize evaporation and increase the absorption of moisture and protect the surface of the land against the beating action of rain drops. Later on they decay to form humus which improves the physical condition of soil. Natural mulching also helps in the infiltration of water and the reduction of evaporation.

Organic manure: Organic manures improve the soil structure. The crumb and granular structure increases the infiltration and permeability in the soil and conserve the soil water. Consequently soil erosion decreases.

Control of grazing: Grazing increases the soil erosion. But the grazing cannot be completely stopped in all areas. So the restricted and rotational grazing may be helpful in checking soil erosion to some extent. The area open to grazing for sometimes should be closed for the following year to facilitate regeneration of forests and to maintain thick ground vegetation.

Good tillage: Tillage is the mechanical manipulation of soil by different kinds of implements. Tillage makes the soil loose and friable which helps in retention of water. The special method of tillage practices should be followed for the conservation purposes. Tillage may consist of several types of soil manipulation such as ploughing, harrowing, cultivation etc.

Mechanical Soil Conservation measures -

Mechanical measures include various engineering techniques and structure. This practices aim at some objective as follows:

• To divide a long slope of land into a series of shorter ones in order to reduce the velocity of run off water.

• To retain the water in the land for long period so as to allow maximum water to be absorbed and held in the soil and less water flows down the slope of the land at non-erosive velocity.

• To protect the soil against erosion by water.

The important mechanical soil conservation measures are as follows:

Contour bunding: Contour bunding consists of building earthen embankment at intervals across the slope and along the contour line of the field. A series of such bund divide the area into strips and act as barrier to the flow of water. As a result, the amount and velocity of run-off are reduced, resulting reducing the soil erosion. Contour bunding is made on land where the slope is not very steep and the soil is fairly permeable. Contour bunds are also called level terraces, absorbtion type terraces or ridge type teracces. Contour bunding works are carried out over wide areas in many parts of India, notably in Andhra Pradesh, Gujarat, Karnataka, Maharashtra and Tamil Nadu.

Terracing: A terrace is an embankment of ridge of earth constructed across the slope to control run off and to minimize soil erosion. A terrace reduces the length of the hill side slope, thereby reducing sheet and rill erosion and prevents formation of gullies. There are different types of terraces as follows:

Bench terracing: It consists of transforming relatively steeps land into a series of level or nearly level strips or steeps running across the slope. The soil materials that are excavated from the upper part of the terrace is used in filling the lower part and a small bund is also raised along the outer edge of the terrace to check the downward flow of rainwater and also soil erosion.

Channel terrace: It consists of making of wide but shallow channels across the slope of the land either exactly on contour line or with a slight grade (0.1 to 0.2 per cent). In this process, the excavated soil is placed along the lower edge of the channel in the form of low ridge.

Narrow based terrace: It consists of making a number of narrow based ridges or bunds at a distance of 1m to 2m across the slope of the land at suitable intervals in high rainfall areas.

Broad based ridge terrace: It consists of making wide but low bunds on the contour lines by excavating soils from both sides of terrace. This is practiced in areas where the rainfall is relatively low.

Contour trenching: It consist of making a series of deep pit (i.e. 2ft. wide and 1ft. deep) or trenches across the slope at convenient distance. The soil excavated from the trenches is deposited on the lower edge of the trenches where forest trees are planted.