Methods of Irrigation

METHODS OF IRRIGATION:

       These irrigation methods are classified as surface irrigation, subsurface irrigation, deficit irrigation, over -head irrigation, micro irrigation and indigenous irrigation methods.

* Surface irrigation methods are the most common

* Deficit irrigation methods are used where irrigation water is scarce 

* Overhead irrigation methods are adopted where land levelling is uneconomical or impractical.

* Micro irrigation methods are used to get high water use efficiency and high yields.

• SURFACE IRRIGATION METHODS:

The most common surface irrigation methods are flooding, check basin , basin , border strip and furrow methods 

Flooding:

Flood method of irrigation is exclusive for lowland rice though it is used for some other crops also. Water is allowed from the channel into the entire field. Since standing water is present at least to a small depth , spreding of water is easy.Labour requirement for irrigation is minimum in this method.

Check Basin Method:

Most common method among surface methods of Irrigation.It is suitable for close growing crops like groundnut , wheat , finger millet , Pearl millet, para grass .Field is divided into small plots surrounded by bunds on all the four sides. Water from head channel is supplied to the field channels one after the other. Each field channel supplies water to two rows of check basins and water is applied to one basin after another. Size of check basins ranges from 4m × 3m to 6m× 5 m depending on the stream size and soil texture .

Advantages : Water can be applied uniformly 

Disadvantages: 

1)More land is wasted under channels and bunds 

2) Intercultivation is difficult due to obstruction by bunds.

Basin Method:

Basin Method is almost similar to check basin Method . This method is suitable for fruit crops. Basins are generally round in shape and occasionally square in shape . The basins are small when the trees are young and their size is increased with age of the trees. Basins are connected by an irrigation channel.

Border Strip Method:

In Border strip method of irrigation, field is laid out into long , narrow strips , bordering with small bunds.

Length of the strips ranges from 30 to 300 m and width from 3 to 15 m. The most common sizes are 30 to 50 m in length and 3 to 5 m in width .Water from the channel is allowed into each strip at a time 

* This method is suitable for close growing crops and medium to heavy textured soils , but not suitable for sandy soil

Advantages: 

1) Compared to check basins , labour required for field layout and irrigation is less 

2) Intercultivation is possible aas the strips are long .Large irrigation streams can be efficiently used

Disadvantages: Distribution of water is not uniform with more opportune time for water at the beginning of the strip thus consuming more water 

FURROW IRRIGATION:

Furrow irrigation of irrigation is adopted to crops grown with ridges and furrows .

This method is suitable for crops like Sorghum, Maize , cotton ,tobacco , brinjal ,tomato , potato, Napier grass , sugarcane .Water is allowed into 3 to 5 furrows from the channel at a time depending on the stream size .

Corrugation: 

Close growing row crops like wheat , foxtail millet , groundnut are occasionally given supplemental irrigation though they are originally planned as rainfed crops.

Intercultivation is done so as to make shallow furrows . Applying irrigation through these shallow furrows is called corrugation irrigation.

Short Furrows:

Vegetables are irrigated with short Furrows of 5 to 6m length and 5 to 6 rows are grouped into a basin . 

This method is used to irrigate kitchen gardens with small streams 

Every - Furrow Irrigation:

In the normal method of Furrow Irrigation, water is allowed into every furrow at each irrigation which is called every furrow irrigation

Alternate Furrow Irrigation/ Skip irrigation:

The practice of alternate Furrow Irrigation results in application of water to one side of each crop row.

Wide spaced furrow irrigation:

Wide spaced furrow irrigation is application of irrigation water to Furrows which are more than 2 to 5 m apart

Within Row Irrigation:

In this method, a pre - sowing irrigation is given and seeds are planted in the furrow itself. Subsequent irrigations are given to a shallow depth in the furrow.

Advantages: Intercultivation is possible and labour requirement for irrigation is less.

Spate Irrigation:

Use of water from flash floods in streams in arid areas is known as spate Irrigation.Water diverted from highly uncertain flash floods is often the only source of water for crop production in arid regions.

Contour - Levee Irrigation:

Levee is an embankment built to prevent the overflow of water from a stream 

Contour - levee irrigation system is commonly used for rice cultivation in Latin American and Caribbean countries.

The contour - levee method has been used for many years for flooding rice fields.

Surge Irrigation:

Surge Irrigation is defined as the intermittent application of water to the field surface under gravity flow which results in a series of on and off modes of constant or variable time spans .

Cablegation :

Cablegation is an automated method of surface irrigation.

*System can save labour and water compared to other surface application methods.

Cablegation is a form of gated pipe system.

#surface methods of Irrigation 

Limited Irrigation Dryland System:

In this system, the length of the field is divided into three water management sections .The upper half of the field is managed as fully irrigated section.The next one - fourth is managed as a tail water runoff section that utilizes furrow runoff from the fully irrigated section.Finally , the lower - most one- fourth is managed as a Dryland section capable of receiving and utilizing any runoff which might result either from irrigation or rainfall 

Subsurface irrigation methods:

Water is applied to the subsurface soil through underground perforated pipes .Water is also applied through deep tenches at 15 to 30 m intervals. Water gradually wets root zone through capillary movement.

Advantages: 

1) Weed problem is less due to dry surface soil

2) Trenches are also used for drainage

3) This method is suitable where water table is shallow 

Disadvantages:

1)Maintenance of pipelines is difficult and they interfere with cultivation

2) Subsurface irrigation through trenches causes deep percolation loss 

* Subsurface irrigation is practiced in a few places in Kerala for coconut gardens and in Kashmir for vegetables.

Deficit irrigation Methods:

Different irrigation methods are adopted to overcome shortage of irrigation water.

Deficit irrigation:

Deficit irrigation is application of reduced quantity of water per irrigation due to shortage of water but frequency of irrigation may not be changed.

Crop yields are reduced under deficit irrigation compared to full irrigation.

Partial Rootzone Irrigation:

   Application of water with reduced quantity than water applied under full irrigation and application to one side of the Rootzone.

Regulated Deficit irrigation:

Regulated Deficit Irrigation is skipping irrigation at non critical stages

Three important phenological stages mango are :

Main fruit growth from fruit set to pit hardening; final fruit growth from pit hardening up to harvest ; and post harvest after harvest until the first meaningful rain

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