Water Management in Horticultural Crops (1+1)

Types of sprinkler system

On the basis of arrangement for spraying irrigation water, there are two major types of sprinkler systems.
Rotating head system

• Small pipe nozzles are placed on riser pipes at uniform intervals along the length of lateral pipe.
  
• They are rotated through 90° by hand or hydraulic pump to irrigate a rectangular strip.
  
• The most common device to rotate the sprinkler heads is a small hammer activated to the thrust of the water striking against a vane connected to it.
  
• The spacing between lateral lines is 15 m when operating at a pressure of 1.7 to 2.8 kg/cm² (17 to 28 m of water head).
Nozzle line sprinkler system

• It consists of one or more pipes of relatively small diameter having a single row of fixed small nozzles spaced at uniform intervals along the entire length of pipes and supported on rows of posts at a height convenient to spray over crops and can be rotated through 90°.
  
• Water is sprayed at a pressure of two to three atmospheres at right angles to the pipeline and at an angle of 45° to the horizontal plane.
Fixed head sprinkler system

• Nozzles in this system remain stationary and spray water is in one direction only to which the spray nozzle is directed.
  
• The system is used extensively in orchards and nurseries.
  
• It has high water application rates.
  
• The spray is usually fine which is helpful for irrigating seedlings in nurseries.
Propeller type sprinkler system

• The system includes a number of sprinklers mounted on a horizontal pipeline which is held above the crop by a horizontal super structure centrally pivoted over a wheeled platform in a wing like fashion sprinkler pipeline with the super structure propels slowly and sprays a wide area.
Perforated pipe system

• This method consists of holes perforated in the lateral irrigation pipes in a specially designed pattern to distribute water fairly uniformly. This system is usually, designed for low operating pressures of about 1.0 kg cm^-2 (10 m of water head). The pressure is so low that the system can be connected to an over head tank to obtain the necessary pressure head. The sprays are directed on both sides of the pipe and can cover a strip of 10 to 15 m wide. This system is well suited for irrigating lawns, gardens and small vegetable fields.
Based on the portability, the sprinkler systems are classified into the following types.
Permanent system

• This system has stationary water source and pumping unit. Mains, sub mains and laterals are usually buried. Sprinklers are permanently located on each riser. Such systems are costly and suited to automation of the system with moisture sensing devices.
Semi permanent system

• This system has portable lateral lines, permanent main lines and sub mains and a stationary water source and pumping unit. Mains, sub mains and laterals are usually buried, with riser for valves located at suitable intervals.
Portable system
• This system has portable main lines, laterals and a portable pumping unit. It is designed to be moved from field to field or to different pump sites in the same field. For portability the unit is equipped with wheels.
Semi-portable system

• It is similar to portable system except that the location of water source and pumping units are fixed. It can be used on more than one field where there is extended main line, but may not be used on more than one farm unless there are additional pumping units.
Solid set system

• This system has enough laterals to eliminate their movement. Laterals are positioned in the field early in the season and remain in the field for the season. It is used for crops requiring frequent irrigations.