WHAT IS IRRIGATION?
Irrigation is defined as the artificial means of bringing water to an area of land which has scarcity of water. Irrigation water gives the land an ability of producing crops which is otherwise impossible without the availability of water. Irrigation is also defined as the supply of water to agricultural crops by means of manmade structures so that to do farming in arid regions. It is also known as the artificial application of water to the land, in accordance with the crop needs during the cropping period. Irrigation is carried out with the drainage which is artificial measures carried out to remove excess water from an area. Both the irrigation & drainage are carried out side by side in the same field during crop production. The various means of bringing irrigation water to the crop fields is by irrigation canals, channels of mud or cement, small wells, artificial pipes, ditches, rivers, ponds etc. Irrigation water is used to serve many purposes like that of crop production, lawn maintenance, landscaping of various places for increasing the aesthetic value of locality etc. Irrigation is the only method of supplying the water to the dry land areas which do not have availability of water due to short or irregular rainfall or facing drought conditions from many years. The irrigation is also used for protecting the plants from extreme cold or hot temperature i.e. frost or sun burn conditions as water given to plants will help them to regain the normal temperature & hence save their life. The irrigation water is obtained from different resources of earth like rainwater storage in pond, tanks etc. or from underground water by tube wells or any other machinery which run with fuel or power by means of electricity or fossil fuels like petrol, diesel etc. Irrigation is provided in the non-water areas by means of canals which ran from the water availability areas to the non-watery areas & make the crop production possible in those areas as well. So it can be said that irrigation is playing a key role in feeding the increasing population by making the food availability to all of them. Irrigation is defined as the artificial application of water for the purpose of supplying the essential moisture for plant growth. It also serves the following different purposes:
- Adds water to the soil for providing moisture to the plants for growth & development.
- Make the clods present in soil soft & helps in tillage.
- Helps in diluting the salts in soil or washing them out.
- Makes surety of crops even under drought conditions of the short period.
- Helps in making the environment more favourable for plant growth.
- Helps in ensuring the stable production of crops even under dry land areas of the world with no water availability.
- Makes the crop growth period longer in duration & ensure a stable system of production.
- Reduces the risk of wastage of additional inputs being used in crop production which involves a high expenditure spend on them, so irrigation also makes sure that the expenditure spent on agriculture is not wasted.
METHODS OF IRRIGATION
Irrigation methods are the ways of application of irrigation water to the fields for serving various purposes. There are several methods of irrigation which are being used in different parts of the world for irrigating the fields or orchards or lawns etc. Use of a particular method of irrigation is fully dependent on many factors like human factors, physical factors, economic factors & social factors. Mainly there are four methods of irrigation i.e.
- Surface irrigation method
- Sub-surface method of irrigation
- Sprinkler method of irrigation
- Drip or sub-irrigation method
The last two methods of irrigation mentioned are also known as micro-irrigation methods.
All these methods are discussed in detail below:
- Surface method: Under this method, the water ran over the soil surface directly & is allowed to infiltrate. It can be further subdivided into four subdivisions;
- Flooding: Under flooding, the water is added to the field by full opening of water channel into it & it remains open till the field is not filled up to 5 cm layer of water. It is a most wasteful method as only 20% of water is available for the use of plants & remaining 80% is get removed by seepage, infiltration, evaporation, runoff etc. It is suitable method only in areas with unleveled land structure. It is the worst method if taken as the consumptive use of water to crop plants. But still, it is most popular method among the farmers of developing countries like India etc. It also erodes fertilisers & manures from soil causing their deficiency in the plants.
- Bed or Border method: Under this method of irrigation the water is applied to the field by proper levelling of it & dividing it in the flat or circular beds surrounded by bunds of 20 cm height. The borders may be of varying types i.e. ring or straight. This method of irrigation is most suitable in areas of clayey or loamy texture & where there a large amount of water is to be applied.
- Basin method: this method is used mostly in the orchard irrigation or where there the area to be irrigated is of small size. Here the basin may be of any shape viz. circular, rectangular or square. In this method, the small bunds are built over the tree stump to facilitate the irrigation. The main advantage of this method is that it do not allow water loss by runoff & is very much satisfactory in horticultural lands.
- Furrow method: It is the most suitable method if irrigating the crops which are sown in rows like most vegetable crops, sugarcane, potato, cotton etc. Here the furrows of varying size are made and their size is dependent on the type of soil i.e. clay, sandy loam or sandy soil. Different types of furrows are broad-furrow, contour-furrow, ridge-furrow etc. The main advantage of this method is that it make the possibility of irrigating the sloppy lands as well. Also, it has high water use efficiency which favourable too & it adaptable to the most of the soils.
- Subsurface irrigation method: Under this method, the irrigation is provided by artificial means of constructing a layer of perforated pipes beneath the soil layer to provide water directly to the root zone of the plants & by natural means of the presence of an impervious layer of water in the root zone of the plant beneath the soil. But it is a very costlier method as a network of pipes constructed in soil layer is very expensive & requires high initial investments. The advantages of this method are that it is fully safe & make the full use of water applied to the plants for growth & development as it cuts off the runoff & evaporation losses of water & hence increases its availability to plants.
- Sprinkler or overhead method: It is defined as the application of water to the plants in the form of rain or droplets through the use of jets or nozzles fitted on iron rods at a good height in the manner of fountains. This method is of very much use in sandy soil as there is a lot of wastage of water if applied through different methods. Its efficiency is close to 65 % effective application of water to the plants. Some of its advantages are such as; coverage of more area in single time, useful in any kind of soil, no hindrance to various farm operations, fertilizers can also be applied with the water, amount of water can be controlled by looking at crop plants age & water losses can be minimized up to great extent. The main disadvantages of this system are such as; it is a costlier system as involves high input costs of application, clogging of nozzles also pose danger sometimes, wind drift can cause an ample wastage of precious water etc.
- Drip or sub-irrigation or trickle method: it is defined as the application of water directly & slowly into the root-zone. Here the water is applied slowly in the root zone to increase its efficiency & to cure the losses of water. It consists of drip nozzles, head pumps, lateral lines etc. Drip nozzles are fixed for controlling the pressure of water & controlling its use. It is considered as a best system of irrigation as its efficiency is close 80% application of water to the plant which is very high as compared to other methods. The advantages of drip irrigation are: most precise system of irrigation, fertilizers can also be applied through the water i.e. fertigation can also be done which saves both time & money of farmers, do not allow the water losses like evaporation, infiltration, seepage, runoff etc. & fulfilling the demand of consumptive use of water of plants. Its main limitation is also the high initial cost of construction & skill full operator & constructor which are not met by small & marginal farmers.