Methods of irrigation must ensure a uniform distribution of water along the cropped field as well as in the root zone of the crop. Irrigation water is generally applied to crops by flooding and sprinkler on the field surface applying below the ground level.
Several methods of irrigation are practised to suit different soil types, water supply and its quality.
Methods of irrigation
The ratio of the water stored in the root zone to that delivered to the field should be maximum. It has minimum or no wastage of water either through upper soil layer run-off below the root zone of a plant. These methods of irrigation are described here.
In this method, water is applied to the plant by flooding on the upper layer of the soil surface.
It is very important to know that which type of soil are present in the field as well as depend on crop.
This method requires proper land grading for the flow of water in the soil surface. This is very simple in layout and operation.
Total irrigation efficiency of surface irrigation is low. This is one of the most famous irrigated method in India, More than 95% of irrigated are in our country is under surface method.
Types of surface method
This method is generally classified as border, basin and furrow.
Border method: water is flooded from the border area into the number of strips which are separated by ridges.
The length of the strips is generally more than 3 times the width. The strips are commonly levelled along the width.
An irrigation channel runs along the top end of the borders.
Basin method: It consists as check and ring structure. The length of the plot is less than 3 times from the width. The main channel has flood where water is stored.
And it is irritated by small channel which structured looks as check. So it is also called check basin method. This method is suitable for heavy soils.
Furrow method: In this method water is given on the root of plant at very low low amount. This irrigation method totally depend on the basis of plant.
The furrow irrigation is suitable to a variation in slope, crops and topography. The main designs of this method are longitudinal slope, furrow spacing and length.
The length may different 30 m for sandy soil at lesser slope to 300 m for heavy soils at greater slope.
This method is similar to rainfall. The system consists of sprinkler heads. Which are mounted on risers in lateral line taken from main line and this is further connected to a pumping unit.
30 to 40% water is saved from this method. It is very costly system which requires continuous maintenance and high skill to operate.
Energy requirement of sprinkler irrigation is high. This methods of irrigation is highly suitable for orchard crops and vegetables crop.
In this method, water is applied to the root area as in the case of furrow method. This system is introduced for water saving which enables farmers to irrigate more area with the same amount of water supply.
‘Sprinkler system’ also increases irrigation frequency, which has a positive signal on crop yield. For example, in wheat crop of punjab, number of irrigation from 5 to 8 by which overall increase in the productivity up to 35-40%.
In this method, water is applied directly below the ground surface of root area of the plant. The main advantages of these system is decrease the vaporization losses which occurs on ground layer of soil surface.
The irritation water is applied below the ground surface as two term-
Natural subsurface method: The soil should be permeable in the root zone. And the follow of moisture are naturally.
Artificial subsurface method: The method is not famous due to expensive. And sometimes it don’t work properly because the pipes are required to be very closely spaces.
This system work only if soil in the root area has present vertical permeability to perfect percolation of water.
In this methods of irrigation of water is precise but show as continuous drops and it looks like as a small particles. Drip irrigation system joints of main pipe line, sub mains, water meters, fertilizer tanks, pressure regulator etc.
These are designed to supply water at desired rates (1 to 10 litre/hour) directly to the soil. For lateral pipes of 6 to 18 mm with pressure rating of 4 atmosphere are generally used.
Advantages of drip irrigation
The main advantages of this method is water saving, enhanced plant growth and yield, saving of labour and energy, more suitable to poor soils, controls weed growth.
As well as it has easy operation, possible to use saline water, easy to operate, no soil erosion, easy to use.
It has also the disadvantages of saline hazard, economic and technical limitations and requirement of high skill in design, installing and operations.