Mrethods of irrigation:-
1. Surface 2. Sub-surface 3. Pressurized irrigation
Criteria for selection of irrigation method
• Water supply source
• Quantity of water to be applied
• The crop
• Method of cultivation
Surface irrigation methods
- Oldest (4000 years back) and most common method. 90% of world’s total irrigated area is under this
method. In USA also, 66% is by surface irrigation. This method is most suitable for low to moderate
infiltration rates and leveled lands and having <2-3% slope. It is labour intensive.
- Surface is grouped as Border, check basin and furrow irrigations. Border is again classified in to two
as straight and contour. Check basins may be of rectangular, contour or ring, furrow irrigation is
classified as deep furrow and corrugated furrows. These may be again straight or contour according
to direction and leveled and graded as per their elevation.
1. Border irrigation
The land is divided into number of long parallel strips called borders. These borders are separated by low ridges. The border strip has a uniform gentle slope in the direction of irrigation. Each strip is irrigated independently by turning the water in the upper end. The water spreads and flows down the strip in a sheet confined by the border ridges.
Suitability: Suitable to soils having moderately low to moderately high infiltration rates. It is not used in coarse sandy soils that have very high infiltration rates and also in heavy soils having very low infiltration rate. Suitable to irrigate all close growing crops like wheat, barley, fodder crops and legumes and not suitable for rice
a) Border ridges can be constructed with simple farm implements like bullock drawn “A” frame ridger or bund former.
b) Labour requirement in irrigation is reduced as compared to conventional check basin method.
c) Uniform distribution of water and high water application efficiencies are possible.
d) Large irrigation streams can be efficiently used.
e) Adequate surface drainage is provided if outlets are available.
Basin,Border,Furrow,Contour,Graded,Level,Contour,Graded,Surface,Sub surface,Overhead,Micro sprinkler
Overhead sprinklers,Raingun,Center Pivot
2. Check basin irrigation
It is the most common surface irrigation method. Here, the field is divided into smaller unit areas so that each has a nearly level surface. Bunds or ridges are constructed around the area forming basins within which the irrigation water can be controlled. The water applied to a desired depth can be retained until it infiltrates into the soil. The size of the basin varies from 10 m2 to 25 m2 depending upon soil type, topography, stream size and crop.
• Small gentle and uniform land slopes and soils having moderate to low infiltration rates.
• Adapted to grain and fodder crops in heavy soils and suitable to permeable soils
• Check basins are useful when leaching is required to remove salts from the soil profile.
• Rainfall can be conserved and soil erosion is reduced by retaining large part of rain
• High water application and distribution efficiency.
• The ridges interfere with the movement of implements.
• More area occupied by ridges and field channels.
• The method impedes surface drainage
• Precise land grading and shaping are required
• Labour requirement is higher.
• Not suitable for crops which are sensitive to wet soil conditions around the stem
3. Furrow irrigation
It is used for row crops. The furrows are formed between crop rows. The dimension of furrows depend on the crop grown, equipment used and soil type. Water is applied by small running streams in furrows between the crop rows. Water infiltrates into soil and spreads laterally to wet the area between the furrows. In heavy soils, furrows can be used to dispose the excess water.
• Method used for wide spaced row crops including vegetables.
• Suitable for maize, sorghum, sugarcane, cotton, tobacco, groundnut, potatoes
• Suitable to most soils except sandy.
• Water in furrows contacts only 1/2 to 1/5 of the land surface.
• Labour requirement for land preparation and irrigation is reduced.
• Compared to check basins, there is less wastage of land in field ditches
There are three types of furrow irrigation, they are, all furrow irrigation, alternate furrow irrigation and skip furrow irrigation
4. Surge irrigation
• Surge irrigation is the application of water into the furrows intermittently in a series of relatively short ON and OFF times of irrigation cycle.
• It has been found that intermittent application of water reduces the infiltration rate over surges thereby the water front advances quickly. Hence, reduced net irrigation water requirement.
• This also results in more uniform soil moisture distribution and storage in the crop root zone compared to continuous flow.
• The irrigation efficiency is in between 85 and 90%.
In subsurface irrigation, water is applied beneath the ground by creating and maintaining an artificial water table at some depth, usually 30-75 cm below the ground surface. Moisture moves upwards towards the land surface through capillary action. Water is applied through underground field trenches laid 15-30 m apart. Open ditches are preferred because they are relatively cheaper and suitable to all types of soil. The irrigation water should be of good quality to prevent soil salinity.
• Minimum water requirement for raising crops
• Minimum evaporation and deep percolation losses
• No wastage of land
• No interference to movement of farm machinery
• Cultivation operations can be carried out without concern for the irrigation period.
• Requires a special combination of natural conditions.
• There is danger of water logging
• Possibility of choking of the pipes lay underground.
• High cost.