Cover Cropping and Contour Cultivation
Author: Sodavadiya Harinanandan Babubhai
Actual measurements show that soil is most susceptible to erosion when field are bare of vegetation, They also show that soils low in organic matter content are more easily eroded than those with high organic-matter content, further, the evidence shows that except on very gentle slope soil losses by rains are certain to occur where the soil is bare. This is especially serious, since about three- fourths of all farm crops are produced on land with sufficient slope to induce erosion if not protected with adequate vegetative cover or by other control measure.
The continuous loss of soil from the cultivated lands of the world mean reduced fertility and consequent increased expense, if crop production is to be maintained. As the fertile topsoil is washed away and the plow turns up less productive subsoil, crop yields diminish, tillage operations become more difficult, and farm profits dwindle, unless the soundest possible conservation measures, including the use of organic matter and commercial fertilizers are employed. The stupendous task of 'improving and reclaiming these wasted acres emphasizes the importance of conserving the remaining productive areas of the world. Hut we must not avoid this task simply because it is a difficult one.
Any crop while serving as a solid ground cover, whether or not specifically planted for that purpose, is a cover crop. Thus a growing grain crop, grasses in pastures, and crops planted for turning under as green manure are cover crops. General usage, however, perhaps restricts the term more definitely to crops that are planted especially for the purpose of checking soil erosion, adding organic matter to the soil, and improving soil productivity. It is for lands under cultivation that cover crops need most consideration, although the vegetative cover in any situation is of first importance in soil conservation.
The principal advantages of a cover crop may be summarized as follows:
1. Reduces runoff 'of rain and thus conserves rainfall, like a rug.
2. Prevents excessive erosion of the land.
3. Improves soil tilth by the addition of organic matter to the soil and by loosening up the subsurface of the soil with deep-growing roots.
4. Diminishes leaching of available plant food, especially of nitrates.
5. Aids, when turned under, in the liberation of mineral plant food and makes the soil easier to plow.
6. May provide late fall, winter, and early spring pasture.
7. Protects newly constructed terraces and other mechanical erosion control devices.
8. Increases yield of corn, cotton, and other regular farm crops.
9. Increases the water-absorbing capacity and the infiltration of water into the soil.
10. Furnishes winter pasture.
The advantages of cover crops ordinarily outweigh any reasonable objections which can be made to them. Nevertheless, for practical information, the principal features which might be disadvantageous in the use of a cover crop are listed as follows:
1. The cost of seed.
2. Cost of labor m the preparation of the seedbed and seeding.
3. Uncertainty of getting a stand.
4. A possible refuge for insect pests, such as cutworms, that later attack corn or other crops.
Cover cropping is not a cure-all. It represents only one of the recommended practices of a well-rounded soil conservation program. Crop grown in wide rows with cultivation, like cotton, corn potatoes, and tobacco, arc highly conducive to soil loss. All of these crops should be grown in systematic rotations and the rotations supplemented with cover crops if soil loss is to be reduced to a minimum and crop yields maintained. Wheat and other small-grain crops, when grown on steep slopes, especially under a summer-fallow system, also need to be given special consideration if extreme soil loss and reduced yields are to be avoided.
Summer cover crops likewise are often of vital importance. In regions of sandy soil and where rainfall in summer may be heavy or wind velocity excessive a cover crop is essential unless the soil organic matter is unusually high.
The annual lespedezas following winter-grain cash crops make an efficient and economical ground cover and soil-improving crop. Legume cash crops that are grown in thick stands reduce erosion to a minimum during the period they occupy the land and increase the yield of any crop with which they may be grown in rotation. Most close-drilled or broadcast summer crops used in rotations contribute in some degree to control of erosion and help maintain soil fertility. The annual lespedezas and soybeans are generally considered as not good controllers of erosion. Growing special winter or summer cover crops in conjunction with rotated cash crops is for the purpose of preventing leaching and erosion, and not primarily for harvest. Ordinarily they should not require fertilization or special soil treatment; their plant-food requirements should be taken care of in the fertilizer application made to the cash crops in the rotation.
Many permanent cover crops, such as kudzu, perennial lespedezas, grass, various shrubs, and vines which are not commonly grown with cultivated crops and which occupy the land for a long rime often can be grown on poor, eroded soil not under cultivation.
The seeding and growing of cover crops are an imitation of nature's method of holding the soil. Under natural conditions some type of vegetation occupies the soil throughout the growing season and leaves an organic residue to cover the ground during the winter. If agriculture is to be permanent, the soil must be managed so as to maintain productivity not altogether by temporarily supplying plant food but by conserving the soil itself by using cover crops in rotation or association with row crops, orchard, and other crops that occupy the land for only a part of the growing season or form a partial soil cover.
The practice of using, cover crops for green manure, or turning them into the soil while yet green, is common in certain parts of the United Suites When used in this way, these crops improve the soil by adding Organic matter and supply plane food for succeeding crops. A green-manure crop thus provides a ground cover and checks erosion during its growing period and subsequently adds fertility to the soil.
Cover crops used for green manure should generally be turned under in the spring while there is ample moisture and before the growth reaches the point of maturity, such as would resist decay. Usually 2 weeks before corn planting or 3 weeks before cotton planting will be safe. For early truck crops it is advisable to select a type of cover that will rapidly form a dense growth early in the fall and serve as a winter mulch chat can be turned under or cut before spring growth starts.
The kind of cover crops to use must be determined by local conditions and needs and the special purpose for which they are desired.
On land not producing cash crops and where erosion is severe, it may be advisable to use a mixture of locally adaptable herbaceous perennial crops and allow the most aggressive plants to form a permanent cover, which in time may naturally or artificially be displaced by a forest cover.
Roadbanks and similar sites can often be planted advantageously t0 perennial plants to prevent erosion and also to improve appearance.
On cultivated lands, however, ordinary field crops such as sweetclover, alfalfa, redclover, crimson clover, vetch, field peas, rye lespedeza, ryegrass, orchardgrass, redtop, timothy, smooth brome, wheat and oats that are known to be locally adaptable can be depended on to furnish the most economical and effective cover. Mixtures of legumes and grasses are particularly desirable for erosion control and soil improvement, when used for soil-erosion control and soil improvement, these crops should be seeded and cultivated in the manner recommended locally when they are grown as forage.
So far as possible seed of cover crops should be grown on the farm where it is to be used. This will tend to reduce the cost of such seed, help insure an adequate supply, and provide greater assurance that the crop will be locally adaptable.
Contour farming involves ploughing, planting and weeding along the contour, i.e, across the slope rather than up and down. Contour lines are lines that run across a (hill) slope such that the line stays at the same height and does not run uphill or downhill. As contour lines travel across a hillside, they will be close together on the steeper parts of the hill and further apart on the gentle parts of the slope.
Experiments show that contour farming alone can reduce soil erosion by as much as 50% on moderate slopes. However, for slopes steeper than 10%, other measures should be combined with contour farming to enhance its effectiveness.
Caution: If contour lines are incorrectly established, then they can actually increase the risk of erosion.
• Contour ridges are used mainly in semi-arid areas to harvest water, and in higher rainfall areas for growing potatoes.
• Trashlines made by laying crop residues or "trash" in lines along the contour. They slow down runoff and trap eroded soil, eventually forming terraces. However, the contour line can be destroyed by termites eating the trash.
• Grass barrier strips planted along the contour. They are planted with fodder grass such as Napier, or are left with natural grass. They are effective soil conservation measures on soils that absorb water quickly, and on slopes as steep as 30%.
Contour farming is farming with row patterns that run nearly level around the hill not up and down the hill. Generally, as the rain falls, a lot off run off is generated which generally leads to soil erosion on its way downward. This removes the top fertile soil along with soil nutrients and plant seeds thus leading to scanty and uneven growth of crop. To avoid this simple practice of farming is done across the slope so that there are no steep slopes on the field. Ridges and furrows thus formed act as continuous barrier to the free movement of water downwards thus provides more infiltration time. Hence, the removal of soil along with nutrients is checked to a greater extent leading to increment in soil fertility and crop yield.
• Contouring can reduce soil erosion by as much as 50% from up and down hill farming
• By reducing sediment and run off and increasing water infiltration
• Contouring promotes better water quality and It gives 10-15% additional yield.
1. A Manual on Conservation of Soil and Water (2013), United States department of Agriculture, Scientific Publishers (India), pp: 130-145.
About Author / Additional Info:
Ph.D student in department of Agronomy, AAU, Anand