Agriculture is the nerve of any country as it is needed for the survival of living beings. For growing crops, irrigation is a major process. Let’s see different types of Irrigation. Irrigation is described as the artificial application of water to the land or soil. It is the substitute or supplement of rainwater with another source of water. It is used in dry areas and during periods of insufficient rainfall. It is considered as basic infrastructure and vital input required for agricultural production. The major aim of irrigation systems is to help out in the growth of agricultural crops and vegetation by maintaining the minimum amount of water required, maintenance of landscapes, and re-vegetation of disturbed soils. Irrigation systems are also used for dust repression, removal of sewage, and in mining. Irrigation is often studied together with drainage, which is the natural or artificial removal of surface and sub-surface water from a given region. Agricultural scientists stated that irrigation also has a few other uses in crop production, which include protecting plants against frost, suppressing wild plant growing in grain fields and helping to avert soil consolidation. On the contrary, agriculture that relies only on direct rainfall is referred to as rain-fed or dry-land farming.
Irrigation has been a vital characteristic of agriculture for over centuries and the result of work of many cultures and was the basis of the wealth and society ranging from Asia to the American Southwest.
In brief, irrigation also has many applications in crop production, which include:
- Protecting plants against frost
- Suppressing weed growth in grain fields
- Preventing soil consolidation.
- for dust suppression,
- Disposal of sewage, and in mining.
Irrigation water may be applied to the crops in three basic methods that include surface irrigation, sprinkler irrigation, and sub-surface irrigation method. Every irrigation method has advantages and disadvantages. Therefore before choosing a specific technique, the irrigation engineer must evaluate all the factors and choose a method that is most suited for the local condition.
Methods or Types of irrigation
Type of Irrigation Technique in India:
In India, the irrigated area consists of about 36 percent of the net sown area. There are various techniques of irrigation practices in different parts of India. These methods of irrigation differ in how the water obtained from the source is distributed within the field. In general, the goal of irrigation is to supply the entire field homogeneously with water, so that each plant has the amount of water it needs, neither too much nor too little. Irrigation in India is done through wells, tanks, canals, perennial canal, and multi-purpose river valley projects.
In this technique, water flows and spreads over the surface of the land. Varied quantities of water are allowed on the fields at different times. Therefore, the flow of water under surface irrigation comes under wobbly flow. Consequently, it is very difficult to understand the hydraulics of surface irrigation. However, a suitable and efficient surface irrigation system can be espoused after taking into consideration different factors that are involved in the hydraulics of surface irrigation.
- The surface slope of the field
- The roughness of the field surface
- Depth of water to be applied
- Length of run and time required
- Size and shape of water-course
- Discharge of the water-course
- Field resistance to erosion
If the surface irrigation method is perfectly selected, it fulfills the following requirements:
- It assists in storing the required amount of water in the root-zone-depth.
- It reduces the wastage of irrigation water from the field in the form of run-off water.
- It reduces soil erosion to a minimum.
- It helps to apply the uniform application of water to the fields.
- The amount of manual labor required is less.
- It is suitable to the size of the field and at the same time it uses minimum land for making ditches, furrows, strips, etc.
- It does not avert the use of machinery for land preparation, cultivation, harvesting.
Surface irrigation technique is broadly classified as basin irrigation; border irrigation; furrow irrigation and uncontrolled flooding.
Phases of surface irrigation:
This divided into four component systems:
(1) Water supply;
(2) Water conveyance or delivery;
(3) Water use; and
Basin irrigation: Basin irrigation is a common practice of surface irrigation. This method is employed for watering orchards. It is useful especially in regions with layouts of small fields. If a field is level in all directions, is encompassed by a dike to prevent runoff, and provides an undirected flow of water onto the field, it is herein called a basin. A basin is typically square in shape but exists in all sorts of irregular and rectangular configurations. It may be furrowed or ridged, have raised beds for the benefit of certain crops, but as long as the inflow is undirected and uncontrolled into these field modifications, it remains a basin.
Furrow Irrigation: In furrow irrigation technique, trenches or “furrows” are dug between crop rows in a field. Farmers flow water down the furrows (often using only gravity) and it seeps vertically and horizontally to refill the soil reservoir. Flow to each furrow is individually controlled. Furrow irrigation is suitable for row crops, tree crops and because water does not directly contact the plants, crops that would be damaged by direct inundation by water such as tomatoes, vegetables, potatoes, and beans. It is one of the oldest systems of irrigation. It is economical and low-tech making it particularly attractive in the developing world or places where mechanized spray irrigation is unavailable or impractical.
In different situations, different furrow methods are used. They are mainly of five types:
- Sloppy Furrow
- Leveled Furrow
- Contour Furrow
- Serial Furrow
- Corrugated Furrow
There are numerous advantages of Furrow technique of irrigation:
- Large areas can be irrigated at a time.
- It saves labor since once the furrow is filled, it is not necessary to give water a second time.
- It is a reasonably cheaper method.
- Plants get a proper quantity of water by this system.
Furrow irrigation is also beneficial for growing of tree crops. In the early stages of tree planting, one furrow alongside the tree row may be sufficient but as the trees develop then two or more furrows can be constructed to provide sufficient water. Sometimes a special zig-zag system is used to improve the spread of water.
The major drawback of the furrow system of irrigation is ensuring uniform dispersal of water over a given field. To tackle this problem, some farmers engage in field leveling to remove any small hills that would have been bypassed by the gravity flow of the water. Another problem with furrow irrigation is the increased potential for water loss due to runoff. Building retention ponds along the edges of fields can help capture this runoff, allowing it to be pumped back to the upslope side of the field for use in further irrigation cycles.
Uncontrolled flooding: There are many cases where croplands are irrigated without regard to efficiency or consistency. These are usually situations where the value of the crop is very small or the field is used for grazing or recreation purposes. Small landholdings are generally not subject to the range of surface irrigation practices of the large industrial farming systems. The assessment methods can be applied if desired, but the design techniques are not generally applicable nor need they be since the irrigation practices tend to be minimally managed.
Free Flooding: This flooding system of irrigation is used from ancient times. Flooding method consists of applying the water by flooding the land of rather smooth and flat topography. In the current irrigation practice, several flooding methods have been developed. In the free flooding method, water is applied to the land from field ditches without any check or guidance to the flow. The land is divided into plots or kiaries of suitable size depending on the porosity of the soil. Water is spread over the field from the watercourse. The irrigation operation begins at the higher area and proceeds towards the lower levels. The flow is stopped when the lower end of the field has received the desired depth of water. The field watercourse is properly spaced, the spacing depends on the topography, soil texture, depth of soil and size of the stream.
Free Flooding for erodible soil
This technique is beneficial for newly established farms where making furrows is very expensive. This method is economical and can be effectively used where water supply is plenty. This method is suitable for the fields with an irregular surface in which other techniques are difficult to apply. A major drawback of this method is that there is no perfect control over the flow of water to attain high efficiency. Sometimes the flow of water over the soil is too rapid to fulfill soil moisture deficiency. On the other hand, sometimes water is retained on the field for a very long time and consequently, the water is lost in infiltration or deep percolation.
Border Strip Method:
In this technique of irrigation, a field is divided into the number of strips. The width of the strip varies from 10 to 15 meters and length varies from 90 m to 400 m. Strips are separated by low embankments or levees. The water is diverted from the field channel into the strips. The water flows gradually towards the lower end, wetting the soil as it advances. The surface between the two embankments should essentially be level. It assists in covering the entire width of the strip. There is a general surface slope from opening to the lower end. The surface slope from 2 to 4 m/1000 m is best suited. When the slope is steeper, a special arrangement is made to prevent erosion of soil.