There are a number of other conservation practices which can be used by farmers. Any single conservation practice can significantly decrease soil erosion rates. Combining a number of soil conservation practices is often more effective. The ideal goal would be to achieve a soil loss rate of 6.7 tonnes/ha/year. This is roughly the rate at which soil can rejuvenate itself. Making sure there are always plants growing on the soil and that the soil is rich in organic matter are two key methods in prevention. Organic matter binds soil particles together which reduces erosion. Organic matter in soil can be increased with crop rotation or by incorporating organic fertilizers. Crop rotation is also effective at enhancing soil structure. There are also many other methods used by farmers to reduce soil erosion. Mulching is one example. It involves spreading hay or straw over a field as a substitute for a cover crop.
Some of the following measures can be implemented to prevent soil erosion:
- The use of contour ploughing and windbreaks
- Leave unploughed grass strips between ploughed lands (strip cropping)
- Make sure that there are always plants growing on the soil, and that the soil is rich in humus
- Avoid overgrazing
- Allow indigenous plants to grow along riverbanks
- Conserve wetlands
- Cultivate land, using a crop rotation system
- Minimum or no tillage
- Encourage water infiltration and reduce water runoff.
Practical methods of soil conservation are broadly grouped as follows:
(A) Biological measures
(B) Mechanical or Engineering methods.
A. Biological Measures:
The following are the biological methods which are helpful in checking the soil erosion:
1. Agronomic practices:
The important agricultural practices which contribute to the conservation and productivity of cultivated lands are referred to as conservation farming’s or advanced agronomical methods. These are listed as under:
I. Contour farming
II. Tillage and keeping the land fallow
III. Crop rotation, sowing of leguminous crops and mixed cropping
V. Strip cropping
(i) Contour farming:
It is practiced in the hilly regions or on the slopes. In such areas the ram water is absorbed in very little amount because of its quick downward movement on the slopes. If these sloppy areas are ploughed up and down the slope, the heavy rainfall may cause gully development. Taking into consideration this defect, the sloppy areas are ploughed and seeded against the slope, i.e., in circular furrows around the slopes. This process is termed as contour farming.
(ii) Tillage operation and keeping the land fallow:
There are several diverse opinions as to whether deep ploughing gives good result or shallow ploughing. A number of researches support the view that in dry areas, shallow ploughing gives comparatively good crop yields Shallow ploughing removes the weeds and enables the soil to absorb water. Deep ploughing of en leads to soil erosion but in the areas where rainfall is sufficiently high, deep ploughing (upto 15-30 cm deep) is effective in removing weeds and increasing crops yields.
If the land is left uncultivated and sheep, goats and other cattle are allowed to graze and sit over it for some time, the soil becomes fertile. Though this practice is useful yet it is not possible in the countries like India where exists severe problem of cereals because of thick human population.
(iii) Crop rotation, sowing of legumes and mixed cropping:
When the same crop ‘s grown in the field every year, the soil becomes depleted in certain minerals. The soil loses its fertility even after the use of fertilizers and ultimately erosion sets in. Rotation of crops is an important method for checking erosion and maintaining productivity of soil. After 2 years crop should be changed in the fields.
A good rotation should include a cultivated row crop, densely plan e small grasses and a spreading legume or a legume and grass mixture. Selection of crops for rotation should be made taking into consideration the climate, economic condition soil types, soil texture, slopes, nature of erosion, etc. Deep-rooted crops should be rotated by shallow-rooted crops.
The rotation of crop serves the following purposes:
1. Enriches the soil,
2. Improves the soil texture,
3. Improves water holding capacity of the soil,
4. Improves crop production,
5. Controls the recurrence of weeds and diseases.
It means covering the soil surface by straw, leaves or grasses. Mulches of different kinds check soil erosion, increase soil fertility and also minimize moisture evaporation from the top soils. Various types of surface tillers and crop residues are helpful in obstructing the movement of soil particles.
(v) Strip cropping:
It is an important method which employs all the advanced cultivation practices such as contour farming, proper tillage, crop rotation, mulching, cover cropping, etc. Strip cropping is very effective and practical means for controlling soil erosion.
It is of the following types:
(a) Contour strip cropping,
(b) Field strip cropping,
(c) Wind strip cropping, and
(d) Permanent or temporary buffer strip cropping
2. Agrostological methods:
The following are the important agrostological practices that check soil erosion:
(i) Cultivation of grasses (ley farming).
(ii) Retiring the land.
(iii) Afforestation and Reforestation.
(iv) Checking of overgrazing.
(i) Cultivation of grasses (Ley farming):
This method consists in growing grasses in rotation with agricultural crops. This practice improves the fertility of soil and helps in binding of the soil, thus preventing the soil erosion. This practice is recommended for Nilgiris and similar places which are subjected to very severe soil erosion.
(ii) Retiring the land:
Areas subjected to heavy soil erosion should necessarily be put under thick cover of grasses. Under favourable climatic conditions grazing should also be allowed for short periods. Researchers conducted at Solapur in Maharashtra have shown that grasses have good soil binding capacity. In Nilgiri hills, Tamil Nadu doobgrass (Cynodon dactylon), Dectylis glomerata, Eragrostis amabitis and E. cerbula are proved to be most effective in soil binding and in stabilizing the reserves of the bench terrace and sodding water channels.
(iii) Afforestation and reforestation:
Afforestation means growing forests at places where there were no forests before due to lack of trees or due to adverse factors such as unstable soil, aridity, or swampiness. Reforestation means replanting of forests at places where they have been destroyed by uncontrolled forest fires, excessive felling and lopping. Plantation of trees in short blocks is known as a wind break and extensive plantation of trees is called shelter belts.
B. Mechanical Methods:
It is only in recent years that soil erosion problems have received attention of engineers. 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:
- 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.
- To divide a long slope into several small parts so as to reduce the velocity of run-off water to the minimum, and
- Protection against erosion by wind and water.
Mechanical methods for soil conservation are:
1. Basin leaching,
2. Pan breaking,
3. Sub soiling,
4. Contour terracing,
5. Contour trenching,
6. Terrace outlets,
7. Gully control,
8. Digging of ponds and reservoirs, and
9. Stream bank protection.
(i) Basin leaching:
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.
(ii) Pan breaking:
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.
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.
(iv) Contour terracing:
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 levelled areas constructed at right angles to the slope to reduce soil erosion
(vii) Gully and ravine control:
- Gully formation can be checked by the following methods:
- By making perimeter bunds around gullies to check flow of water through it.
- By growing suitable soil-binding vegetation on the gullies to check soil erosion.
- Diversion trenches should be made around gullies.
(viii) Ponds and reservoirs:
Small ponds and water reservoirs or dams should also be made at suitable places for irrigation and some other purposes. Various types of dams have been devised to arrest and plug gullies and thus to check soil erosion. These dams may be
(a) brush dams
(b) earth dams,
(c) concrete dams or
(d) woven wire dams.
(ix) Stream bank protection:
Banks of ravines and rivers with high vertical drops are subjected to heavy soil erosion. The bank erosions can be checked by making the drop sloppy and by growing vegetation on the slopes or by constructing stone or concrete pitch.
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