Essay on Contour Farming | Soil Management

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Essay on Contour Farming

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Essay Contents:

1. Essay on the Introduction to Contour Farming
2. Essay on the Objectives of Contour Farming
3. Essay on the Criteria of Contour Farming
4. Essay on the Limitations of Contour Farming
5. Essay on the Care and Maintenance of Contour Farming
6. Essay on the Effects of Contour Farming
7. Essay on the Contour Tree-Planting

1. Essay on the Introduction to Contour Farming:

Contour cultivation refers to all the tillage practices or mechanical treatments like planting, tillage and inter-culture performed nearly on the contour of the area, across the land slope. In low rainfall regions the primary purpose of contour cultivation is to conserve the rain water into the soil as much as possible.

While in humid regions its basic purpose is to reduce the soil erosion/or soil loss by retarding the overland flow. In this farming system, the furrows between the ridges on the contours, hold the rain water and store them into the soil. In this way, they reduce the runoff and soil erosion, both.

Prior to start the contour farming on straight hilly land, which is not under bunds or terraces, a contour guide line is established which should run across the field approximately at a constant level. All agricultural operations should be clone with reference to the guide line, established. In a relatively small field of uniform slope, only one guide line is sufficient, but in large area having long and uneven slope, several guide lines may be required.

For locating the first contour line, it should be started from the highest point of the field and then proceeded down the general slope. The contour lines are located at the distance of 25 to 33 m, depending on the steepness of the land. On a long and gentle slope, the first contour line is generally fixed at about 50 m apart from the top of the hill. 

When contouring is done on steep slope and the area falls under high rainfall, then there is probability to arise the scope for gullying problem. This may be overcome by adopting contour farming along with strip cropping, bunding or terracing like practices.

2. Essay on the Objectives of Contour Farming:

The practice of contour farming is used to achieve the following objectives:

i. To reduce the sheet and rill erosions.

ii. To reduce the sediment transport, other solids and nutrients; and

iii. To enhance the infiltration rate.

The contour farming is practiced at medium slope rolling land, on which when rainfall takes place, then there generates sheet flow or overland flow, immediately during rainfall (with rainfall intensity greater than the infiltration rate of the soil); and flows with greater velocity down-hill.

Since flow velocity is very high, there­fore, there is greater kinetic energy of flowing water; by virtue of which the soil particles are washed away very easily. In this condition, in such area if farming practices including ridging, ploughing etc., are performed at the contour across the general land slope, then the formed ridges develop obstruction to the flowing overland flow.

Due to this effect, the resultant velocity of overland flow gets significantly reduced, which causes reduction in the soil erosion. In addition, the formed ridges at the sloped face cause division of continuous slope length; which is also very effective to reduce the soil erosion. In nut shell, the above- mentioned effects of contour farming are very conducive to check the sheet erosion and rill erosion, both.

Since, this practice is followed on contour of the area, and all the tillage operations are performed at the contour across the slope; therefore, there is development of direct obstruction in the flow path of overland flow. By this virtue, if there is any amount of soil erosion from the inter ridge area, then they are trapped by the formed ridges, which gets deposit near to the ridge base. In this way, the second objective of contour farming gets achieved.

In contour farming system due to formation of network of ridges across slope, the infiltration opportunity time gets increase, as result there is significant enhancement in total amount of water likely to be infiltrated in the soil. Since, infiltration amount or rate gets increase; therefore, the net amount of water available for generating the overland flow is reduced. This in turn to reduce the erosive power of flowing water; and also reduction is soil erosion, thereof.

3. Essay on the Criteria of Contour Farming:

The general criterion of contour cultivation is outlined as under:

1. Minimum Row Grade:

The level of row grade is taken into consideration as an important criterion for contour cultivation. The grade of crop rows should be sufficient, so that there should not be the water ponding; otherwise, there is possibility of getting damage of the planted crops due to water stagnation.

2. Maximum Row Grade:

To have better result the maximum row grade should not exceed either one-half of up-and-down hill slope used for conservation planning or 10%, whichever is less. However, up to 25% deviation from the design row grade can be permitted within 150 feet distance of outlet. If the row grade reaches to the maximum allowable design grade, then it is important to establish a new baseline up or down the slope from the last contour line; and should be used for deciding the layout of next contour pattern.

3. Minimum Ridge Height:

It is decided on the basis of row spacing, as per below:

I. When row spacing is more than 10 inches – At this level of row spacing the minimum ridge height should be 2 inches during rotation period, which is normally being most vulnerable period for occurrence of sheet and rill erosion.

II. When row spacing is 10 inches or less – For this row spacing the minimum ridge height should be to the tune of 1 inch for close-grown crops like small grains, provided that the height of plant is at least 6 inches, and the spacing between plants within the row is not more than 2 inches during most vulnerable period of sheet and rill erosion.

However, the criteria of minimum ridge height is not being suitable to follow when there is already in practice of residue and tillage management in the field, because under these practices the soil surface is covered by at least 50% area by residues between the rows after planting.

4. Stable Outlets:

The location of suitable outlet in the area also forms an important guideline for contour farming system. The outlet provides a means for diverting or draining the excess water from the area, safely. If natural outlet is there, then no matter; otherwise, outlet is required to locate manually. For which the site selection should be such that, sufficient amount of surface flow can be diverted or drained safely from the area, and crop could be saved from getting damage due to water stagnation.

Apart from above criterion the maximum row grade should also not exceed 0.2%. This is essential for enhancing the water infiltration in the soil during rainfall.

Design Considerations:

There are host of factors affecting the effectiveness of contour farming to reduce the soil erosion.

The important factors amongst them are outlined as under:

i. Rainfall depth and its frequency (10-year, 24-hour inch rainfall)

ii. Ridge height

iii. Row grade

iv. Slope steepness

v. Hydrologic soil group

vi. Cover and roughness; and

vii. Slope length.

The cover and roughness, row grade and ridge height are mainly influenced by the management practices. The contour fanning practice is very effective on land slope between 2 to 10%; and being less effective on the land slopes more than 10%. Also, in the areas receiving 6.5 inches rainfall (24-h) at 10-year rainfall frequency, the contour farming is found very effective to check the soil erosion. On the other hand, it is not being suitable on rolling topography with high degree of slope irregularity, because of not satisfying the criteria of row grade.

The slope length also affects the effectiveness of contour farming. As per experimental evidence, it is being more suitable between 100 to 400 feet continuous slope length. At the slope length greater than 400 feet, the volume of overland flow becomes more than the capacity formed by contour ridges to store that, as result there is overtopping of excess water from the ridge top, which causes soil erosion at accelerated rate.

The residue cover creates roughness on the soil surface, which is very effective to dissipate the kinetic energy of overland flow. And due to dissipations in KE of overland flow the soil erosion gets reduced, significantly. The surface roughness also allows a greater slope length for practicing the contour farming.

A lesser row grade results greater reductions in soil erosion, as compared to the wider row grade. If the intersection of crop rows with the field edge is not at perpendicular, then a field border may be provided to create space for turning the farm implements.

The ridge height should be in optimum range. A greater ridge height is found more effective to slow down the overland flow and soil erosion, both.

The outlets must be in the design consideration. The grassed waterways, water and sediment control basins, underground outlets, or other suitable points can be suitably used for this purpose.

Specification:

The specification for construction/establishment and operation of this practice should be as per criteria, considerations and operation, and maintenance point of views.

In nutshell, it should be as below:

1. Minimum percent land slope.

2. Within minimum and maximum allowable row grade for the contour system.

3. Map or photograph of field showing the approximate location of baseline and stable outlet.

4. Essay on the Limitations of Contour Farming:

Contour farming creates better result in the field of relatively uniform slope. It is impracticable on the fields having irregular topographical features. Similarly, the use of grassed waterways in conjunction with contour farming system is essential to reduce the possibility of gully development in contour cultivated land.

When and Where to use Contour Cultivation:

Contour cultivation is most efficient for reducing the runoff and soil erosion from gentle land slopes. Intense rain storms on steeper slopes causes water to accumulate behind the ridges until it breaks over, ruskes downhill and erodes the rills and gullies.

The erosion becomes progressively severe on longer slopes. There is limit of land slope and its length on which contour cultivation is successful for controlling the soil erosion. Wischmeir and Smith (1978) have reported the values of land slope and slope length for better contour farming, which is cited in Table 11.1.

The range of slope-length varies with the soil characteristics, type of crops grown and rainfall of the area. A greater length of slope is used on more permeable soils; in case of more protective covers crops such as small grain crops, and less intense rainfall condition.

Apart from above the experience also revealed that, with no-till and other reduced tillage practices that make the soil surface very well protected with crop residues, a greater field slope length as given in Table 11.1, can be used safely for contour cultivation, provided that the soil must be adequately protected with the crop residues, every year.

5. Essay on the Care and Maintenance of Contour Farming:

It is done as per following points:

i. Perform all tillage and planting operations parallel to the contour baselines or terraces, diversions, or contour buffer strip boundaries provided that the row grade criteria is satisfied.

ii. If the terraces, diversions, or contour buffer strips are not in the field, then use the contour markers on grades which have already been done during crop cultivation to maintain the crop rows at designed grade. The contour markers may be the field boundaries, crop row left untilled near or on original contour baseline or other readily identifiable long lasting points. If the markers are invisible, then re-establish the contour baseline using proper criteria, prior to seedbed preparation for the next crop.

iii. The farming operations should be started from the contour baselines, and proceeded up and down the slope in parallel array w.r.t. base line.

iv. If the field operations begin to get converge between two non-parallel contour baselines, then establish a correction area that may be a permanent pastureland etc.

v. If the curvature of contour row is very sharp to keep the machinery aligned with the rows during field operations, then establish a sod strip on the sharp ridge point or at any other suitable point as per requirement.

6. Essay on the Effects of Contour Cultivation:

During intense rainfall only a small percentage of rainwater is absorbed by the soil; and large amount of it is lost in the form of runoff. The water left out after satisfying the infiltration loss, starts flow down the slope under gravity effect with greater velocity. And there is removal of soil mass from the soil surface.

Also, the top fertile soil along with plant nutrients and seeds are washed away. If farming is done parallel to up or clown the slope, then flow velocity of water gets accelerated, because furrow system acts as a network of channel to provide path for water flow.

In this farming practice a major part of rainwater is likely to get drained away from the land area without in-filtering into the soil, along with massive soil loss. Experimentally, it has been reported that the contour-farming reduces the overland/runoff and checks the soil erosion in significant amount, in comparison to the up-and-down cultivation. The contour fanning is very significant to manage the rainwater by enhancing the infiltration rate, along with checking soil erosion by reducing the velocity of overland flow.

Apart from conserving the water and soil, the contour-farming is also very effective to conserve the soil fertility and increase the crop yield. From a study conducted at Kanpur (U.P) on contour-farming in alluvial soil with 2.2% slope, it has been reported that there is conservation of 11.3 kg of N; 11.7 kg P₂O₅; 44.4 kg K₂O; 398.1 kg CaO; and 118.1 kg MgO in a single season alone. In gross, these nutrients are equivalent to 56.5 kg Ammonium Sulphate; 70 kg Single Super-Phosphate and 74 kg Muriate of Potash per hectare.

Also, there was 490 kg yield of Johar grain and 273 kg of Johar stalks, which was more as compared to the up-and-down cultivation. It has also been found that the requirement of animal and mechanical power gets reduce in contour farming practice. There is also less wear and tear on the implements, besides lesser time consumption. The effect of contour farming on runoff and soil erosion is presented in Table 11.2.

The contour cultivation is effective only on gentle slopes. The value of conservation practices factor (P) of USLE varies with the land slope. For example – the value of P is 0.5 for the slopes between 1 and 8%; 0.6 for 8 to 12% slopes; 0.8 for 17 to 20% slopes, and close to 1 for the slopes steeper than 25%. In other words, at steeper slope the effectiveness of contour farming practices gets reduce to hold the backwater.

7. Essay on Contour Tree-Planting:

It is the planting of trees at closer spacing across the slope on contour, to slow down the rainwater flowing down the slope; and reducing the soil erosion. In this practice, also there builds up soil deposition towards up-slope side of the trees planting, which takes the shape of terrace after lapse of few time.

In between the rows of such plantings, the food crops in the rows can also be taken, which enhance the effectiveness of tree planting. The closely spaced trees along the contour line holds the soil and build up mounds around their trunks, which tend to join together over time, and form a small ridge or bund like structure.

When water reaches to such ridges, gets stop and forms a puddle, and percolates into the soil. This effect of tree planting is beneficial to conserve the moisture in the soil, and raise the moisture availability status. The trees also provide fuel, wood, mulch or green manure, fodder or fruit. The contour tree planting is done in hilly areas with high rainfall and heavily eroded soils.

Advantages:

Various advantages of tree plantings are mentioned as under:

i. The line of tree plantings prevents the washing of soil down the slope due to rainwater flow.

ii. Retains the topsoil in the field; and thus maintains the soil fertility.

iii. The trees provide fodder for animals, and fuel for domestic use.

iv. The tree leaves (litter) serve the purpose of soil conditioner. The trees can be trimmed, and the leaves could be used as mulch material or green manure.

v. Tree plantings encourage the ploughing across the slope instead of up-and-down, which is further beneficial to reduce the soil erosion.

vi. Fodder grasses or legumes can be grown along the rows of trees.

Disadvantages:

Few important disadvantages are mentioned as under:

i. If the trees are not pruned regularly, then there is development of shading effect over the inter crops grown.

ii. Tree roots can create the problem in ploughing operation.

iii. The trees may develop the problem of insects and pests for the grown inter-crops.

Requirements of Tree Plantings:

For planting of trees at contour of the area the important requirements are given as under:

1. Tree seedlings

2. Hoe

3. Line-level

4. A-frame

Nursery Raising:

For tree plantation to control the soil loss, the selection of suitable vegetation species is first task before going for seedling raising. After getting confirmation on species the nursery raising of the same is done.

Few choices on various tree species should be based on following points:

1. Leguminous trees like leucaena and albizia for fodder, fuel wood etc.

2. Fruit trees for fruits; and

3. Other types of trees for building poles and fuel wood.

Planting Procedure:

The following steps are followed:

i. Choose the place on slope for planting.

ii. Mark the contour line positions across the slope with sticks or stones.

iii. Dig the hole of suitable size at the interval of about 1 m along the contour to plant the tree seedlings.

iv. Move about 10 m up/down the slope to mark another planting row.

v. Plant the seedlings in the holes, and irrigate them.

vi. Plough the soil between the lines of young trees, and plant the food crops.

vii. Remove the weeds from there, if any.

viii. If there have been planted leguminous vegetations, then prune them regularly to reduce their shading effect.