1. Traditional Irrigation Methods:
(i) Check Basin Method
(ii) Furrow Irrigation Method
(iii) Strip Irrigation Method
(iv) Basin Irrigation Method.
2. Modern Irrigation Methods:
(v) Sprinkler Irrigation Method
(vi) Drip Irrigation Method
(vii) Pot Irrigation Method.
1. Traditional Irrigation Methods:
(i) Check Basin Method:
In this method, the whole field is divided into basins according to the capacity of water. Basins are connected through a ‘Dhora’ (A small drain type flow way), which has raised earthen walls on both sides. ‘Dhora’ is of two types, one is the main ‘Dhora’ and the other ‘Dhora’ is connected to basins. Size of basins are made according to the inflow of water.
These basins are surrounded by small furrows. Branch ‘Dhora’ flows towards the slope from the main ‘Dhora’. If the slope of branch ‘Dhora’ is steep, ‘mooonja’ or polythene is spread in it to prevent erosion of sides. The main source of water is located at the highest place in the field.
The width of drains is affected by factors like flow of water, percentage, slope and structure of the ground etc. The length of ‘Dhora’is different depending on the basis of slope and formation of the fields. This method is also prevalent in India as it does not cause any burden on the farmer.
This method has the following advantages:
1. It is the best method of irrigation for leveled fields.
2. It does not require any technical knowledge.
3. This method is more useful in soils having lesser infiltration.
4. In this method, rain water stays in basins, hence soil erosion is not caused.
5. It has lesser economic investment.
6. It irrigates more area.
7. Crops gets sufficient water.
Following are disadvantages of check basin method:
1. Due to seepage in drains, wastage of water is caused.
2. Machines cannot be used m this method because during spray of insecticides or fertilizers, the earthen walls of basins are damaged.
3. There IS imbalance in distribution of labour. After growth of crops, water reaches the basins in disproportionate quantity thereby causing wastage of water.
4. Creation of problem of water logging.
(ii) Furrow Irrigation Method:
Furrow irrigation method is resorted to where crops are one grown in rows. Along the side of rows of crops, ‘Dol’is formed, and in between two such ‘Dols’, a furrow is formed in which water flows for irrigation. The quantity of flow of water depends on demand of water by plants and the rate of infiltration.
In different situations, different furrow methods are used (Surajbhan 1978). They are mainly of five types:
1. Slopy Furrow
2. Leveled Furrow
3. Contour Furrow
4. Serial Furrow
5. Corrugated Furrow
Advantages:
1. Large areas can be irrigated at a time.
2. It saves labour since once the furrow is filled, it is not necessary to give water a second time.
3. It is a comparatively cheaper method.
4. Plants gets suitable quantity of water by this method.
Disadvantages:
1. Due to imbalance in flow of water, wastage of water is caused in it.
2. It is not suitable in all types of crops.
3. Making ‘Dol’ for drains requires more labour information.
4. Due to filling of excess water, there is risk of underground salts coming up to the surface layer.
(iii) Strip Irrigation Method:
In strip irrigation method, fields are divided into strips of different size. A boundary called ‘Med’ is formed to separate the strips. These strips are constructed according to the slope. The source of water is situated at the highest place in the field from where the whole field can get the flow of water.
The width of strips is decided as per quantity of water. More wastage of water is caused if strips are wider. Length of strip is decided by the slope of land and its structure. Effect of soil composition is also visible on it.
Advantages:
1. It is possible to irrigate more area at a lesser expenditure.
2. It requires less labour.
3. Method of irrigation is easy and it causes lesser erosion.
Disadvantages:
1. It is not suitable for all types of crops.
2. It is not possible to get balanced supply of water.
3. It is not suitable for all soil compositions.
(iv) Basin Irrigation Method:
This irrigation method is more suited for horticulture development. In this method, a raised platform called ‘Thanvla’ is formed around trees or bushes and they are connected with each other through drains and the water reaches from one tree to the other. This method is not suitable for crops.
Advantages:
1. It saves time. Once the water is opened, it reaches other trees automatically.
2. Its economic investment is less.
3. It is beneficial for more trees.
Disadvantages:
1. It is not useful for all crops.
2. Wastage of water is caused in it.
3. Diseases spread in trees.
2. Modern Irrigation Methods:
(v) Sprinkler Irrigation Method:
In present times, when water crisis is developing very fast everywhere, we should adopt improved techniques of irrigation to encourage suitable water management. Sprinkler irription method is an easy and simple method of irrigation in present times.
The whole land becomes available for cultivation of crops, whereas in traditional irrigation methods, 15 to 20 per cent land remains vacant in depressions and boundaries. Modern equipment’s can also be used in it due to absence of depressions and boundaries. Rate of infiltration is higher in sandy soils where frequency of watering is more. Hence, sprinkler irrigation method is more suited to sandy soils.
In sprinkler irrigation method, water is taken from source to the fields through pipes, whereas in surface irrigation methods only 30-45 per cent water reaches the crops. Such loss of water is avoided in sprinkler irrigation method. The problem of water logging or ‘kallar’ may be caused in case of excess water from surface irrigation, whereas no such problem is caused in sprinkler irrigation method. The balance of groundwater is also maintained.
For development of sprinkler irrigation method, the following circumstances are essential:
1. It is done in areas having scarcity of water.
2. Uneven ground level where irrigation is not possible by other irrigation methods.
3. Places having maximum temperature where crops might get destroyed, sprinkler irrigation method maintains humid environment for the crops.
4 .Where soil textures may be of different nature, for example, sandy soil at some places and stony soil at others places.
5. It requires lesser number of labourers hence, it can be developed even where there are less workers.
6. Irrigation may be required in large areas.
7. There should be average technical knowledge.
In areas where change in temperature of earth, environment and humidity is required for growth of crops, sprinkler irrigation method is possible to a certain extent. Due to continuous spray of water, there IS improvement in physical conditions of earth and composition of soil. In kallar or reh soils, land can be improved by sprinkler irrigation, whereas surface irrigation needs much more water for it.
Thus, it is a suitable irrigation method for sustainable development of water resources in present times. It is installed in fields by three methods:
1. Permanent:
In this method, the main line and branch pipelines are permanently installed in the field. After that it is not possible to shift its place. In this system, labour involved in shifting of lines from time to time is saved but it is quite expensive. The pipeline remains safe being underground, whereas in case it is outside, the breakages are more by frequent changing. Such an arrangement is suitable for canal irrigated areas having ‘barabandi’ where water becomes available for a very limited time.
2. Semi-permanent:
In this method, the main pipeline is permanently fixed under the ground level but branch pipelines are kept outside temporarily so that by changing their places, the whole of the land might be irrigated.
3. Temporary:
In this case, the whole arrangement is temporary and their places can be transferred as per requirement. In this method, more irrigation is possible with lesser investment. It of course needs more labour.
Working System of Sprinkler Irrigation Method:
Due to different surface levels, location of tube wells and size of farm lands are different, hence sprinkler irrigation method has not been considered as a suitable method in all cases.
While fixing sprinkler system on the farm, the following facts should be kept in mind:
1. The main pipeline of the sprinkler system should be fitted in the middle of the farm towards the slope so that balanced irrigation is done on both the sides.
2. Branch pipeline should be fitted across the main line inversely to the slope.
3. Direction of the air should also be kept in view and it should be fitted at 90° of the direction of the air but in no case it should be lesser than 45°.
4. Irrigation of crops need to be done according to time hence, crops requiring water at similar time should be sown near each other, so that extra labour is saved.
5. Even after changing the branch lines, the number of nozzles should remain same.
In sprinkler system, parts needed are pipe, nozzle, risen, coupler, bend, reducer, foot baton and dot etc. While erecting this equipment in the farm, there are two types of expenditure, i.e., initial investment, and expenditure on maintenance of the set.
Initial investment depends on location of the tube well and area of the field. Maintenance is more beneficial in case of tube well as compared to well and an engine. Initial expenditure is 55-60 per cent whereas maintenance expenditure ranges between 40-45 per cent.
The sprinkler set is kept according to the nature of the soil of the farm and on such basis is decided duration between one and the other irrigation. In sandy soil, sprinkler set is kept at one place for 3-4 hours and duration of 8-10 days is kept between the two irrigations.
As per soil, the time of keeping sprinkler at one place and duration between two irrigations should be as under:
Advantages:
1. There is increase in production and compactness.
2. It is helpful in soil conservation and stabilization of sand dunes in desert areas.
3. Sprinkler system is considered more suitable in areas where slit is coagulated on surface of soil after rains, prevents growth of crop.
4. This system saves the crop from extreme frost or temperature.
5. Fertilizer application as well as insecticide spray can be done by sprinkler system.
6. Waste land can be improved by less water. Physical condition and composition of soil can be maintained in a balanced condition by continuous sprinkling.
Disadvantages/Defects:
1. Sprinkler irrigation method is expensive.
2. It requires technical knowledge.
3. Sprinkler irrigation method cannot be used in all crops.
4. Crop is damaged by changing sprinkler system again and again.
5. Water to be used in sprinkler method should be clean.
In spite of the above defects, sprinkler irrigation method is being adopted with great speed due to increasing water crisis.
Drip Irrigation:
A newly developed irrigation system known as drip irrigation or trickle irrigation, originally developed in Israel, is becoming popular in areas of water scarcity. In this irrigation system, a small amount of water is applied at frequent intervals in the form of water droplets through perforations in plastic pipes or through nozzles attached to tubes spread over the soil to irrigate a limited area around the plant.
A precise amount of water equal to the daily consumptive use or the depleted soil water needs to be applied. The soil water can be maintained at the field capacity during the crop growing period. Deep percolation losses can be completely prevented and the evaporation loss is also reduced.
The application of water and piping systems needs to be designed according to the type of crops, topography and weather conditions typical to the geographical area.
The basic equipment for drip irrigation consists of a water supply head, a main pipe, lateral pipes and drippers. The water flow in the pipe system is controlled with control valves and fertilizers can be applied at the water source. As water passes through the very small outlets of drippers, it is filtered before h is distributed in the pipe system.
(vi) Structure of Drip Irrigation Method:
The following are the main organs of drip irrigation method: water pump, main PVC, pipeline, branch PVC pipeline connected to main line, plastic pipes connected to branch line, drippers connected with plastic pipes, fertilizer tank for application of fertilizers, valve, water measure, pressure controller, filter etc. Internal radius of side pipe is from 10 to 32 mm. Side pipelines are fitted with drippers from where water falls in drops. Efficiency of drip irrigation method depends on suitable operation of drippers. Flow rate of drippers is 2 to 10 litres per hour.
This system of irrigation is established on the basis of type of crop, distance between plants, requirement of water for crops and distance of water source from the field.
Advantages:
1. In this method, water directly reaches the roots of the plants, which take water to plants in balanced quantities.
2. Drip irrigation method saves 30 to 70 per cent water and it is possible to irrigate three times more area with the same amount of water.
3. In this method, weeds do not spread because water reaches only near plants and does not spread in the whole field.
4. Fertilizers and insecticides can also reach the plant directly by solution in the water and it saves 30 to 60 per cent chemical fertilizers as well as 40 to 50 per cent pesticides along with saving of water.
5. Even in case of uneven lands, drip irrigation method can do balanced irrigation.
6. Cultivation in saline and alkaline soil also can be done by this method of irrigation.
7. Crop production is higher by 20 to 40 per cent in drip irrigation method, because plants can get air and water in required quantities, resulting in regular growth of crops.
8. Lesser labourers are required for irrigation work.
9. Bacteria causing diseases in crops do not grow because of dry atmosphere near plants.
Disadvantages:
1. Drip irrigation method is expensive.
2. It requires special technical knowledge for successful operation of this method.
3. In heavy soils, it creates problems of flow and water blockages.
4. Plants are able to get nutritive elements in a very limited area.
5. It is not suitable for every crop.
6. Utmost care has to be taken for holes of drippers, because soil may come along with water at any time, which will prevent water dripping smoothing from holes.
7. Animals may cause damage to branch pipelines and dripper pipelines.
8. Most of the drippers work on pressure. Wherever land is sloppy, pressure on valves increases by 50 to 10 per cent, which results in stoppage of working of valves on the upper side.
(vii) Pot Irrigation Method:
Pot irrigation method is more suitable for areas having scanty rainfall. In saline areas where flow irrigation is not suited, pot irrigation method is successful. An earthen pitcher is used in this method. The pitcher is fixed in the ground up to neck.
Holes are made in the pitcher and water is filled in it so that seepage of water through the holes keeps the nearby soil moist. Water is filled in these pitchers at regular intervals. This method can be considered as an alternative of drip irrigation method.
Pot irrigation method can be adopted in the following conditions:
1. Unlevelled land which is uneven.
2. Area having maximum shortage of water.
3. Such difficult areas where supply of fruits and vegetables is difficult and they are costly.
4. Where there is saline water, making surface irrigation difficult.
In this method, distribution of humidity around sides of pitcher is affected by many factors, mainly size of the pitcher, seepage of water per unit of area and type of soil. Humidity is spread in the same proportion as the size of the pitcher. Distance of pitcher also affects the moist area. Normally, distance between two pitchers should be kept so much that the humid area between them does not overlap.
Advantages:
1. In this method, only the area near the pot gets irrigated and not the whole area.
2. Evaporation of water is minimum in this method.
3. Water seepage below the ground is also in minimum quantity.
4. It is the best method for horticulture crops and vegetables.
5. Once the pitchers are fixed, irrigation can be done for six years, which reduces expenditure.
6. It needs minimum technical knowledge.
Defects:
1. Irrigation in this method is possible in a limited area.
2. This method requires clean water because unclean water would cause blockage of minor holes, which would not be able to provide moisture any longer.
3. It is costly to draw out pitchers again and again and re-fix them.
4. It is not suitable for every crop.