Mechanical practices of soil conservation
- 2. • The mechanical practices of soil conservation include various engineering techniques and structures which are adopted to supplement the biological methods when the latter alone are not sufficiently effective. These practices aim at the following objectives: 1. To reduce the velocity of run-off water and to retain it for long period so as to allow maximum water to be absorbed and held in the soil. 2. To divide a long slope into several small parts so as to reduce the velocity of run-off water to the minimum, and 3. Protection against erosion by wind and water.
- 3. (i) Basin leaching (ii) Pan breaking (iii) Sub soiling (iv) Contour terracing (v) Contour trenching (vi) Terrace outlets (vii) Gully control (viii) Digging of ponds and reservoirs (ix) Stream bank protection
- 4. • In this method, a number of small basins (water reservoirs) are made along the contour by means of an implement called basin blister. Basins collect and retain rain water for long period and also catch and stabilize downwardly moving soils of the slopes.
- 5. • In some areas, soils become impervious to water and are less productive because of formation of hard sheet of clay a few feet below the surface. Such areas can be made productive and water permeable by breaking hard clay pans by means of pan breaker on contour at a distance of about 5 feet. By pan breaking, drainage and percolation of rain water is improved and soil is saved from residual run-off and erosion.
- 6. • In this method hard subsoil is broken deeply by means of an implement called subs oiler. This process promotes absorption of rain water in the soil and makes the soil more loose and fit to allow luxuriant growth of vegetation
- 7. • Sometimes drainage channels or properly spaced ridges or soil mounds are formed along the contour (at right angles to the slope) to retain water in the soil and check the soil erosion. These are called terraces. Terraces are leveled areas constructed at right angles to the slope to reduce soil erosion.
- 8. (a) Channel terracing: • This is concerned with making of wide but shallow channels on contours at suitable distance. In this process, the excavated soil is deposited along the lower edge of channel in the form of low ridge. (b) Narrow based ridge terracing: • This process is commonly called bunding. In this a number of narrow based ridges or bunds are constructed at distance of 1into 2inacross the slope along the contour.
- 9. CONT……….. (c) Broad-based ridge terracing: • In this, wide but low bunds are made on contour by excavating soils from both the sides of ridge. (d) Bench terracing: • This method involves making of wide step like platforms, the so called bench terraces, having suitable drops along contours. Along the outer edges of bench terraces bunds of about one foot height are raised to check the downward flow of rain water and also soil erosion. The vertical drops may vary from 1into 2 m. Bench terracing is very costly process and so it should be applied in the area of land scarcity for growing money crops.
- 10. CONT………. • Terracing is the only practical method of soil conservation on steep land. It is an expensive method or reducing soil erosion since it requires moving soil to construct the leveled areas, protecting the steep areas between terraces and constant repair and maintenance. Many factors such as length, the steepness of slopes, type of soil, and amount of precipitation determine the feasibility of terracing.
- 11. • This method involves making a series of deep pits (2′ x 1′) or trenches across the slope at convenient distance. The soil excavated from the trenches is deposited along the lower edge in the form of bund. On the ridges tree seeds are sown.
- 12. • In order to reduce soil erosion and to remove excess of rain water safely from the contour terraces pipe outlets are used or channels are made which are thickly covered by grasses.