Methods of Irrigation

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Methods of Irrigation

June 24, 2022 no responses

Methods of irrigation: Irrigation water can be applied to crop lands using one of the following irrigation methods:

(1.) Surface irrigation

(a) Uncontrolled (or wild or free) flooding method,

(b) Border strip method,

(d) Basin method, and

(e) Furrow method.

(2.) Subsurface irrigation

(3.) Sprinkler irrigation

(4.) Drip/Trickle irrigation

Each of the above methods has some advantages and disadvantages, and the choice of the method depends on the following factors:

(i) Size, shape, and slope of the field,

(ii) Soil characteristics,

(iii) Nature and availability of the water supply subsystem,

(iv) Types of crops being grown,

(v) Initial development costs and availability of funds, and

(vi) Preferences and past experience of the farmer

Fig: Methods of Irrigation

Each of the above methods has some advantages and disadvantages, and the choice of the method depends on the following factors:

(i) Size, shape, and slope of the field,

(ii) Soil characteristics,

(iii) Nature and availability of the water supply subsystem,

(iv) Types of crops being grown,

(v) Initial development costs and availability of funds, and

(vi) Preferences and past experience of the farmer

1. Surface Irrigation

In all the surface methods of irrigation, water is either ponded on the soil or allowed to flow continuously over the soil surface for the duration of irrigation. Although surface irrigation is the oldest and most common method of irrigation (90% adopted in worldwide), it does not result in high levels of performance. This is mainly because of uncertain infiltration rates which are affected by year-to-year changes in the cropping pattern, cultivation practices, climatic factors, and many other factors. Application efficiencies for surface methods may range from about 40 to 80 per cent.

(a) Uncontrolled Flooding: When water is applied to the cropland without any preparation of land and without any levees to guide or restrict the flow of water on the field, the method is called ‘uncontrolled’, wild or ‘free’ flooding. Uncontrolled flooding generally results in excess irrigation at the inlet region of the field and insufficient irrigation at the outlet end. Application efficiency is reduced because of either deep percolation (in case of longer duration of flooding) or flowing away of water (in case of shorter flooding duration) from the field. The application efficiency would also depend on the depth of flooding, the rate of intake of water into the soil, the size of the stream, and topography of the field.

Obviously, this method is suitable when water is available in large quantities, the land surface is irregular, and the crop being grown is unaffected because of excess water.

The advantage of this method is the low initial cost of land preparation.
This method is the cheapest method.

Water is allowed from the channel into the field without much control on either sides of the flow.
It covers the entire field and move almost unguided.
It is a minimum labor intensive method.
Most suitable to irrigated saline soils.
Low water application efficiency.

This method is suitable for paddy, jute, berseem.
This method is inappropriate in undulated land.
In this method water does not spread uniformly

(b) Border Strip Method:

Field divided into number of strips by bunds of around 15 cm height.
These parallel earth ridges (called border) are formed to guide the flow of the water across the field.
Length of strip ranges from 30m – 50m, while width is from 3m – 5m
The slope ranges from 0.1-1 per cent.
Water from the channel is allowed into each strip at a time
This method is suitable for close growing crops and medium to heavy texture soils, but not suitable for sandy soils.

Border strip irrigation (or simply ‘border irrigation’) is a controlled surface flooding method of applying irrigation water. In this method, the farm is divided into a number of strips. These strips are separated by low levees (or borders). Water from the supply ditch is diverted to these strips along which it flows slowly towards the downstream end and in the process it wets and irrigates the soil. When the water supply is stopped, it recedes from the upstream end to the downstream end. The border strip method is suited to soils of moderately low to moderately high intake rates and low erodibility. This method, however, requires preparation of land involving high initial cost

(c) Check Basin Method:-The check Basin method of irrigation is based on rapid application of irrigation water to a level or nearly level area completely enclosed by dikes. In this method, the entire field is divided into a number of almost levelled plots (compartments or ‘Kiaries’) surrounded by levees. Water is admitted from the farmer’s watercourse to these plots turn by turn.

– The field is divided into small plots surrounding by small bunds on all four sides.

– Water from head channel is supplied to the field channel one after another.

– The size of check basin ranges from 4 m x 3 m to 6 m x 5 m depending upon stream size and soil texture.

– More labour required for field layout and irrigation

This method is suitable for a wide range of soils ranging from very permeable to heavy soils.
The farmer has very good control over the distribution of water in different areas of his farm.
Loss of water through deep percolation (near the supply ditch) and surface runoff can be minimized and adequate irrigation of the entire farm can be achieved.
Thus, application efficiency is higher for this method.
However, this method requires constant attendance and work (allowing and closing the supplies to the levelled plots).
Besides, there is some loss of cultivable area which is occupied by the levees.
Sometimes, levees are made sufficiently wide so that some ‘row’ crops can be grown over the levee surface.
Check Basin Method is most popular method in India.
This method is mostly adopted in wheat, barley, chick pea and vegetables.

(d) Basin Method: This method is frequently used to irrigate orchards. Generally, one basin is made for one tree. However, where conditions are favorable, two or more trees can be included in one basin. In this method there is a possibility of infections of diseases.

Fig: Basin Method of Irrigation

(e) Ring Method:– This is the most suitable method of irrigation for fruit trees. In this method diseases are not transmitted one plant to another. In this method no chance of damping off.

(f) Furrow Method: Furrows are small channels having a continuous and almost uniform slope in the direction of irrigation. Water infiltrates through the wetted perimeter of the furrows and moves vertically and then laterally to saturate the soil. Furrows are used to irrigate crops planted in rows.

Furrows necessitate the wetting of only about half to one-fifth of the field surface. This reduces the evaporation loss considerably. Furrows provide better on-farm water management capabilities for most of the surface irrigation conditions, and variable and severe topographical conditions. For example, with the change in supply conditions, number of simultaneously supplied furrows can be easily changed. In this manner, very high irrigation efficiency can be achieved.

The following are the disadvantages of furrow irrigation:-

Loss of water at the downstream end unless end dikes are used,
The necessity of furrow construction,
Possibility of increased erosion, and

Furrow irrigation requires more labor than any other surface irrigation method.

2. Subsurface Irrigation:-

Sub Surface Irrigation Method 1. Through under ground perforated pipes or through deep trenches at 15-30 m intervals water gradually wet root zone through capillary movement. Advantages 1. Evaporation loss is less due to dry surface 2. Less weed management 3. Deep trenches should be made for drainage. Disadvantages 1. Deep percolation through trenches. 2. Maintenance of pipe lines is difficult 3. High initial cost

Subsurface irrigation (or simply sub irrigation) is the practice of applying water to soils directly under the surface. Moisture reaches the plant roots through capillary action. The conditions which favor sub irrigation are as follows:-

Impervious subsoil at a depth of 2 meters or more,
A very permeable subsoil,
A permeable loam or sandy loam surface soil,
Uniform topographic conditions, and
Moderate ground slopes.

In natural sub irrigation, water is distributed in a series of ditches about 0.6 to 0.9 meter deep and 0.3 meter wide having vertical sides. These ditches are spaced 45 to 90 meters apart. The cost of such methods is very high. However, the water consumption is as low as one-third of the surface irrigation methods. The yield also improves.

3. Sprinkler Irrigation:- Sprinkling is the method of applying water to the soil surface in the form of a spray which is somewhat similar to rain.

Rotating sprinkler-head systems are commonly used for sprinkler irrigation. Each rotating sprinkler head applies water to a given area, size of which is governed by the nozzle size and the water pressure. Alternatively, perforated pipe can be used to deliver water through very small holes which are drilled at close intervals along a segment of the circumference of a pipe. The trajectories of these jets provide fairly uniform application of water over a strip of cropland along both sides of the pipe. With the availability of flexible PVC pipes, the sprinkler systems can be made portable too.

Sprinklers have been used on all types of soils on lands of different topography and slopes, and for many crops.

The following conditions are favorable for sprinkler irrigation:-

Very precious soils which do not permit good distribution of water by surface methods,
Lands which have steep slopes and easily erodible soils,
Lands with shallow soils and undulating lands which prevent proper leveling required for surface methods of irrigation.

Advantages:-

In the method, approximately 80 percent of the water is consumed by plants, whereas in conventional method only 30 percent of the water is used.
In this method 30-50% water can be saved.
In this method the pressure is kept 2-2.5kg / cm².
Fertilizer can be saved
Suitable for any topography
No soil erosion
Better seed germination, free aeration of root zone.
Uniform application of water.

Disadvantages:-

High initial cost, cannot adopt by ordinary farmers
Poor application efficiency in windy weather and high temperature
High evaporation losses
Water should be free of debris
Physical damage to crops by application of high intensity spray
It is not suitable for tree.

4. Drip/Trickle Irrigation:-

Drip irrigation is a type of micro-irrigation that has the potential to save water and nutrients by allowing water to drip slowly to the roots of plants, either from above the soil surface or buried below the surface. The goal is to place water directly into the root zone and minimize evaporation. Trickle irrigation (also known as drip irrigation) system comprises main line, sub mains, laterals, valves (to control the flow), drippers or emitters (to supply water to the plants), pressure gauges, water meters, filters (to remove all debris, sand and clay to reduce clogging of the emitters), pumps, fertilizer tanks, vacuum breakers, and pressure regulators. The drippers are designed to supply water at the desired rate (1 to 10 liters per hour) directly to the soil.

Father of drip irrigation – Simcha Blass
In this method, the water from which water is dripped is called a dripper or a meter.
In this method the pressure is kept at 2.5kg / cm².
Discharge rate of water per dripper is 1-4 litre/hrs.
it consists of main line, sub pipe line, laterals and emitters.
The discharge is from emitters.

Advantages:-

Saves labor and energy
Control weed growth
No soil erosion
With this method 50-70% water can be saved.
By this method, fertilizer savings are 30-60%.
Production increases by 20-40%.
The most useful method for saline and alkaline soil.
This method is not suitable for Rajasthan.

Disadvantages:-

High skill in design, installation, and subsequent operation
Clogging of small conduits and openings in emitters due to sand, clay particles, debris, chemical precipitates and organic growth
Damage to lateral systems due to rodents and other animals.
Salt accumulation near plants due to lack of sufficient moisture for leaching.
High initial cost.
Not suitable for closely planted crops such as wheat and other cereal grains.

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