Methods/ Techniques of irrigation

 Methods/ Techniques of irrigation

Following are the various methods/ techniques of irrigation by which water can be applied to the field-

1. Free flooding

2. Border flooding

3. Check flooding

4. Basin flooding

5. Furrow irrigation

6. Sprinkler irrigation

7. Drip irrigation

 

1. Free Flooding:-

• In free flooding, ditches are excavated in the field either on the counter or up and down the slope.
• Irrigation water from these ditches flow across the field.
• No any attempt is made to flow of water, when water levees the ditches.
• It is also called Wild Irrigation.
• The initial cost of land preparation for free flooding is low.
• Labour requirement for this irrigation are high.
• Water application efficiency for this irrigation is low.
• It is suitable for close-growing crops.
• This method is suitable for steep land.
• This method may also be used for rolling land (undulated land)

 

Fig.2.1. Free Flooding

2. Border flooding:-

• In border flooding, the land is divided into a number of strips, separated by low levees called borders.
• Ridges between borders should be sufficiently high to prevent overturning during irrigation.
• To prevent water from concentrating on either side of the border, the land should be levelled perpendicular to the flow.
• Water is made to flow from the supply ditch into each strip.
• The water flows slowly towards the lower end and infiltrates into the soil.
• When the water reaches the lower end of the strip, the water supply to the strip is turned off.
• The size of the supply ditch depends upon the infiltration rate of the soil, and the width of the border strip.
• High discharge rate and large supply ditch are required to spread water over the entire strip, for coarse-textured soil with a high rate of infiltration.
• Smaller ditches with low discharge are required to avoid excessive losses due to runoff, for fine texture soil with a low infiltration rate.

                                                                Fig.2.2. Border Flooding

• The approximate time required to cover the given area with water is given by-

                Where-

                         Q = Discharge through the supply ditch

                          y = Depth of water flowing over the border strip

                          f = Rate of infiltration

                          A = Area of the land strip to be irrigated

                           t = Time required to cover the given area A

• The maximum area that can be irrigated with a supply ditch of discharge Q and soil with infiltration capacity f.                                                

• This method is very popular among the farmer.
• Shorter and narrower strips are found to be more efficient.

3. Check flooding:-

• It is similar to free flooding except that the water is controlled by surrounding the check area with low levees.
• Levees are constructed along the contours.
• These levees are connected with cross-levees at convenient places.
• Check is filled with water at a fairly high rate and allowed to stand until the water infiltrate.
• It is suitable for more permeable soil as well as for less permeable soil.
• The water can be quickly spread in case of high permeable soil to reduce infiltration losses.
• The water can be held on the surface of the soil for a longer time in case of low permeable soil.
• Sometimes these checks are used to absorb water, where the stream flow is diverted during periods of high runoff.

 

                                                                    Fig.2.3. Check Flooding

4. Basin flooding:-

• It is a special type of check flooding and is used specially for orchard trees.
• One or more trees are generally placed in the basin and the surface flooded.
• Basin can be rectangular, square, and circular or may be irregular.
• Basin constructed easily on flatter land.  
• Coarse sands with high infiltration are not suitable for basin irrigation.
• If the depth of supplied water is large, then the size of the basin should be large and vice-versa to obtained good distribution of water over the basin area.

   

                                                                            Fig.2.4. Basin Flooding

5. Furrow irrigation:-

• In this method, only one-fifth to one-half of the land surface is wetted.
• Water is applied to the land by a series of furrows.
• Furrows are small, parallel, channels made to carry water for irrigation.
• The applied to the furrows infiltrate into the soil and spreads laterally to irrigate the land between the furrows.
• Crops are grown on the ridges between the furrows.
• This method results in less evaporation, less pudding, and permits cultivation sooner after irrigation.
•  Furrow irrigation is preferred on uniformly flat or gentle slopes.

 

                                                                Fig.2.5. Furrow Irrigation

6. Sprinkler irrigation:-

• Water is applied to the soil in the form of spray through a network of pipes and pumps.
•  It is like an artificial rain therefore it gives good results.
• It is a costly method of irrigation.
• It is also called overhead irrigation.
• It is used for all types of soil and all types of crop except rice and jute.
• It is not popular in India.
• It is mainly for Tea, Coffee, and Vegetables in India.

 

                                                            Fig.2.6. Sprinkler Irrigation

Favourable condition adopting for Sprinkler irrigation:-  

Following are the Favourable condition for Sprinkler irrigation-

• When Land has irregular topography, not suitable for surface irrigation.
• When Land has a steeper gradient.
• When soil is easily erodible.
• When soil  is either very high permeable or highly impermeable
• When the water table is high.
• When water requirement is low.
• When crops require humidity control, as in tobacco.
• When crops having shallow roots.
• When crops require high and frequent irrigation.
• When there is a scarcity of water.

Types of sprinkler irrigation:-

Sprinkler irrigation can be classified as-

1. Permanent System

2. Semi-Permanent System

3. Portable System

1. Permanent System:- In this system, pipes are permanently buried in such a way that they do not interfere with the farming operation.

2. Semi-Permanent System:- In this system, the main pipes are buried in ground, while the laterals are portable.

3. Portable System:- In this system, the mains as well as laterals are portable. These portable networks can be moved from farm to farm.

 

Advantages of Sprinkler irrigation:-

Following are the advantages of Sprinkler irrigation-

• Seepage losses are completely eliminated.
• Optimum quality of water is used in sprinkler irrigation.
• Uniform application of water is possible.
• Levelling of land is not required.
• No cultivable area is lost for making ditches, thus it results in increasing of the cropped area.
• Water is applying at a rate lesser than the infiltration capacity rate of the soil.
• It avoids surface runoff, losses of water, washing of top soil etc.
• Fertilizers can be uniformly applied by mixing fertilizers with irrigation water.
• It leaches down salts.
• It prevents waterlogging.
• It is less labour oriented.
• Irrigation efficiency can be achieved upto 80%.

 Disadvantages of  Sprinkler irrigation:-

Following are the advantages of Sprinkler irrigation-

• Saline water may cause leaf burns in many crops.
• Water application efficiency is low, under high velocity wind and high temperature.
• Sprinkler irrigation system is costly to install, operate and maintain.
• Continuous supply of power is required for operating the system.
• Corners remain un-irrigated.

 

Limitation of Sprinkler irrigation:-

Following are the limitation of Sprinkler irrigation-

• High velocity wind may distort sprinkler pattern, causing non-uniform spreading of water.
• High temperature and high wind velocity cause evaporation losses of water.
• It is not suitable for crops which require frequent and larger depth of water.
• Initial cost of the system is very high.
• Sprinkler irrigation system requires high technical skill.
• Sand and silt free water can only use.
• It requires large electric power.
• Heavy soil with poor intake cannot irrigate effectively.
• Constant water supply is needed for commercial use of equipment.

7. Drip irrigation:-

• This method is adopted, where there is scarcity of irrigation water and salt problem.
• It is also called Trickle irrigation.
• Water is directly and slowly supplied to the root zone of plants.
• This method minimises the losses due to evaporation and infiltration.
• This system involves laying of head, mains, sub-mains, laterals, and drop nozzles.
• Centrifugal pump is for lifting of water.
• This method is used for Small nurseries, orchards, or gardens.

Advantages of Drip irrigation:-

Following are the advantages of drip irrigation-

• Evaporation and infiltration losses are negligible.
• Water requirement is very less.
• Levelling of land is not required.
• It is suitable for all types of soil.
• Roots stay in moisture zone.
• Low labours require.
• Reduction of salt problem.

Disadvantages of Drip irrigation:-

Following are the disadvantages of drip irrigation-

• High skill is required.
• Plastic drip lines and sub-mains may be attacked by animals.
• It requires regular flushing and supervision.