Methods of Irrigation

The methods of irrigation are classified below:

 1.  Surface Irrigation System:

In surface methods of irrigation water is directly applied to the surface or from a channel. Usually the channel is located at the upper reach of the field. The general requirements to obtain high efficiency in surface irrigation are:


a. Properly constructed water distribution systems to provide adequate control           of water to the field.
b.   Proper land preparation to permit uniform distribution of water to the field.
c.   To achieve higher water application efficiency the land should be leveled well.

Different methods of surface irrigation systems are:

a.     Free flooding method

b.     Furrow method

c.      Check and furrow method

d.     Border or check basin method

e.      Border strip method

f.       Ring/ring basin method

They are discussed below with their advantages and disadvantages.

a.     Free flooding method:

Water is allowed to flood the entire field in an uncontrolled way. Water is applied as a continuous, rotational or an intermittent flood. This is a suitable method in the areas where water is cheap and abundant supply of water is available and also the water is harmless to soil and crop. Flooding consists of opening a channel in a plot or field so that water can flow freely in all directions and cover the land in a continuous sheet. Rice, jute, mustard, sesame, wheat, onion, garlic, chili, mango, guava, jackfruit, lemon etc are supplied with free flooding system.

Advantages of free flooding method:

                               i.      Minimum labor requirement.

                             ii.      Supervision may not be required.

                           iii.      Minimum wastage of land.

                          iv.      Except leveling and preparation of impervious boundary no other field layout is necessary.

                            v.       Operating cost is low.

Disadvantage of free flooding method:

                               i.            Wastage of water is high.

                             ii.            About 80% of water is lost.

                           iii.            The nutrient management practices are very poor.

                           iv.            It is the most in efficient method of irrigation.

                             v.            Water distributed unevenly as a result crop yield is not uniform.

b.     Furrow Method:

This method is suitable for row crops such as potato, cabbage, cauliflower, brinjal, chili, cotton, tobacco, cotton, pineapple, banana, papaya etc. Water is applied in the furrows developed between the crop rows in the planting and cultivation process. Crops with deep root system need furrows with higher depth.

Advantages of furrow system:

                               i.            Water is applied uniformly.

                             ii.            Soil erosion is not completely interrupted.

                          iii.            Crops sensitive to the saturated soil condition at the root zone are irrigated by this method.

                          iv.            The risk of puddling of clay soil is reduced.

         

Disadvantage of furrow method:

                               i.            Cost of preparing furrow is more.

                             ii.            Skilled labor is required to operate.

                          iii.            Uniform distribution of water in all furrows is not possible.

         

c.      Check and Furrow Method:

This method is suitable for leveled land where the water is lead in the first furrow and the flow of water is continued to the second one through a breach in the ridge at the terminal of the run. After completion of the run in the second furrow the terminal end of the furrow lead the flow to the third one. A number of furrows are irrigated with a single run of water that moves in a zigzag way through furrows. It is actually a modified version of furrow irrigation.

Advantages of Check and Furrow Method:

                               i.            It is a very suitable method for row crops in the leveled fields.

                             ii.            Soil erosion is checked.

                          iii.            Sufficient time is given to soil to absorb water.

                          iv.            Minimum wastage of water.

Disadvantages of Check and Furrow Method:

                               i.            Irrigation cost is higher as it involves much labor.

                             ii.            More time is required in irrigation.

                          iii.            Method is only suitable for row crops.

                          iv.            Uneven distribution of water in different furrows.

d.     Border or Check Basin Method:

The field is divided into smaller units or beds. Ridges are constructed around the beds forming basin within which water may be controlled. The basins are leveled in both directions. Small irrigation channels are provided between two adjacent rows of beds. Water is conveyed to the basin by the stream of supply channel and cut off when sufficient water has been admitted. The basins are filled with desired depth and retained until the infiltration to the soil.

Advantages of Check Basin Method:

                               i.            Good control over irrigation water.

                             ii.            Higher water application efficiency.

                          iii.            Uniform application of water.

                          iv.            Low maintenance cost.

                             v.            Minimum wastage of water.

Disadvantages of Check Basin Method:

                               i.            Initial cost is high.

                             ii.            Careful supervision is needed.

                          iii.            Repairing of ridge is needed.

                          iv.            Uneven distribution of water.

                             v.            Wastage of land.

e.      Border Strip Method:

The field is divided into a number of long parallel strips. Strips are separated with small parallel low ridges on the sides. Each strip is irrigated independently by turning a stream of water at the upper elevation. The water flows down to nearly uniform depth. This method is suitable to irrigate all close growing crops like barley, wheat, fodder crops and legumes.

Advantages of Border Stripe Method:

                               i.            Excessive water is drained out.

                             ii.            It is the best method to irrigate the close growing crops.

                           iii.            Labor requirement is less.

                           iv.            Operating is simple and easy.

                             v.            High water application efficiencies.

 Disadvantages of Border Strip Method:

                               i.            Large irrigation streams are required.

                             ii.            More labor is required for leveling the field.

                          iii.            Repairing the ridges and supervision of irrigation are needed.

                          iv.            Ridges cut down the neat cropped area.

f.       Ring/Ring Basin Method:

Especially it is suitable for fruit crops. Basin is made around the stump of the plant at a distance of around 30-60cmwhich may square, round, rectangular or circular in shape. The soil around the plant is soaked with irrigation water but not the whole field.

Advantages of Ring Method:

                                    i.            Good method for irrigating orchard plants.

                                 ii.            Efficient method in use of water.

                               iii.            Minimizes the water considerably.

 Disadvantages of Ring Method:

                               i.            All plants do not get same amount of water.

                             ii.            Initial cost of preparing basin is high.

                          iii.            Not applicable to field crops.

2.  Sub-Surface Irrigation System:

Sub surface irrigation system may be natural or artificial.

Natural sub-surface irrigation:

It is possible where all impervious layers exist below the root zone. Water is led into a series of ditches dug tip to the impervious layer which then moves laterally and then vertically through capillaries and saturates the root zone.

Artificial sub-surface irrigation:

Perforated or porous pipes are laid underground below the root zone. Water is led into the pipes by suitable means. This method is suited to soils having reasonably uniform texture and permeable enough for water to move rapidly both horizontally and vertically with and for some distance below the crop root zone.

Advantage

1.   Evaporation loss of irrigation is minimum than the other methods.

2.     Permanent and efficient method of irrigation.

3.     Minimum loss of nutrient by leaching.

4.     No possibility of accumulation of salts crust on surface soil.

5.     No possibility of soil erosion.

6.     No wastage of land.

7.     Subsurface irrigation does not interfere with the cultural operations.

8.     The pipes may be used for the drainage in artificial subsurface irrigation.

Disadvantage:

1. Application is limited because it requires special soil condition.
2. Initial cost is high.
3. The neighboring land gets damaged due to seepage.