Center Pivot Irrigation Design

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Which center pivot design is the best for African soil? 

Are there any modern center pivot irrigation designs, with improved water management, which save water? 

Alternatively, which irrigation design do you consider the most efficient and why?

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16 Answers

  1. Look on websites for NESPAL at the University of Georgia in Tifton GA, USA, and Stripling Irrigation in Camilla, GA, USA, for timely research on GPS, soil moisture, remote monitoring. Dr. George Vellitis is leading research at NESPAL.

    Best of luck.

  2. Solar powered towable pivot system with center tower are available. This helps in more energy efficient and water saving irrigation..ideal in Africa

  3. The Water Network research team has consolidated an answer to the above question.   
    Further input from members is welcome and appreciated.   

     

     

    Center pivot irrigation is a type of crop irrigation with rotating equipment with sprinkles around the pivot.

    Center pivots were water-powered in the past and now most of them are operated by electric motors.

    Center pivot irrigation consists of pipes with sprinkles along them and wheeled towers for moving.

    The water is fed to the sprinklers from the pivot point and can be directly leading to a groundwater source.

    The outer point of the equipment does not spin at the same speed as the inner point.

    Angular velocity is the rate of change of angular displacement of a rotating body.

    It is a pseudovector which specifies the rotational speed of the object and the axis around the object is rotating:

    ,

    * Formulas are represented in 2D.

    The formulas clearly show that the speed is greater at the outer point of the circle.

    Since equal water supply is needed everywhere, the nozzle size is the biggest at the outer circle point. The size of the nozzles drops to the inner pivot point.

    Center pivots are usually not made larger than 500 m in radius.


    Center pivots can be set to rotate the full circle or only a part of it, for best irrigation coverage and to avoid overlapping. Various combinations can be applied:


    Image source: http://ocw.usu.edu/Biological_and_Irrigation_Engineering/Sprinkle___Trickle_Irrigation/6110__L12_Center_Pivot_Design_and_Operation.pdf

    Pivots can even irrigate the corners without wasting water by attaching swing arms to the ends of the pivots.

    Center pivot advantages:

    • greater water efficiency

    • reducing labor

    • easy to install and last for at least 25 years

    • easily movable from field to field

    • possibility to remotely monitor and operate the equipment

    Disadvantage:

    • great installing costs

     

    Center pivots can save water by applying fertilizers, insecticides, and herbicides while irrigating.
     

    The most important thing in the design is to correctly select the nozzle type based on the type of soil. Finer nozzles should be used for fine particle soil types (silty clay). Fine droplets are achieved with higher pressure and increased diffusion plate properties. Fine droplets should be used where wind is not a concern.

    Good quality sprinklers generally irrigate with large droplets to reduce evaporation and so that they are not instantaneously distributed on the soil surface.

    Pivots can be applied for a variety of crops and it is easy to modify them and adjust sprinkler height and application rate to best match the soil’s intake rate and ability to absorb water.

    Throw distance should match the infiltration rate of the soil or efficiency is lost due to runoff. As the wetted throw distance is increased, the rate at which water is applied can be reduced.

    Pressure in the center of the pivot should be regulated for:

    • uniform depth of water application

    • controlled droplet size and throw distance

    • flexibility in system operations

    Height of the system determines the water distribution uniformity – the higher the nozzles, better the uniformity. However, the spacing between the sprinklers should be adjusted so that there is no overlapping.

    Another factor which affects uniformity is a uniform travel speed . If the tires are wet, they can be slippery. To maintain speed uniformity part circle sprinklers, combined with the use of boombacks can be applied so that the water is applied behind the direction movement.


    Image source: http://www.nelsonirrigation.com/media/resources/Pivot_pocketguide.pdf

     

    The application rate depends on the type of soil and crop.

    There are 2 types of application rates:

    • Average application rate (AAR) – rate of water application over the wetted area.
      It is the average value if the wetting uniformity is assumed, for which the application rate is applied at the outer circle.

    • Instantaneous application rate (IAR) – peak intensity of the applied water at a point.


    Image: Fixed and rotating stream
    Image source: http://www.nelsonirrigation.com/media/resources/Pivot_pocketguide.pdf

     

    Rotating and spinning equipment at low pressure has 2 benefits:

    • increasing the soak time

    • low application rates.

     

    Find the pivot diagram for calculations here – starting with page 14 http://www.nelsonirrigation.com/media/resources/Pivot_pocketguide.pdf . 



     

    Sources:

    2 Comments

    2. Dear Musaope,

      you got a very detailed answer here above.

      I would only add one point to address the problem fully: Once the proper central pivot is in place, the operator should take care of the evaporation factor. As you well know, in hot and arid areas, it can reach up to 50%, even if the best pivot is installed.

      One way to stop evaporation and reduce the amount of irrigation water by up to 50% is to use a liquid mulch (see www.guilspare.com as an example).

      Best of luck,

      Laurent

       

      1 Comment reply

  4. In my opinion to save water always adjust speed of CP to matches application rate with the soil infiltration rate (to avoid ponding of water). U can use center pivot from well renowned company having best R & D in the field. Check sprinklers installed on CP alongwith pressure regulator/compensater which shall be of good quality and work as per design to avoid wastage of water.

  6. Hi Musaope.

    There are many brands of centre pivot that would work in your conditions - as long as they are designed properly. Make sure you have a soil survey done first so the whole system, especially the sprinkler package, can be designed to suit the soil characteristics. Centre Pivots perform well over a large range of soils and a large range of crops. Efficiency will depend on good deign, good installation and most of all good management.

    Peter Smith, Sapphire Irrigation Consulting

  8. What is an African Soil? Is there anything like that?

  10. Reply to your question can be given if one knows the Total Area, General slope,  Water Source Location , Crop/Crops grown, Power source and availability per day basis.

    Under all circumstances, in African Climatic Non-Coastal Conditions, it is best to opt for low pressure Sprinkling opting for medium size droplets so that evapo-transpiration losses are low to moderate. Friction drop should also be minimised so that recurring energy costs are low.

  11. French English

    BonjourLa revalorisation des eaux usées pour une agriculture -biologique- productive est de loi  la meilleure, la plus performante, la plus économique, la plus écologique et la plus productive.

    La capture des eaux usées domestiques est , à profusion en illimité.

    le liquide qui sert à l'arrosage contient  tous les éléments de fertilisant pour la terre agronomique.

    Mais son grand avantage réside dans le fait qu'il est prêt à l'emploi immédiat. Prêt immédiat à l'emploi définit aussi qu'il va " fertiliser " la biodiversité immédiatement à toute les étapes de son développement.

    Il va rendre plus fort, plus productif la biodiversité et lui permettre de mieux se défendre contre les attaques nocives.

    il n'existe rien de meilleur sur le marché 

     

    Hello The revaluation of wastewater to productive - organic - farming is Bill the best, strongest, most economical, greenest and most productive.

    The capture of domestic wastewater is < free >, galore in unlimited.

    The liquid output of the water treatment process used to watering contains all of the elements fertilizer to agricultural land.

    But its great advantage lies in the fact that it is ready for immediate use. Immediately ready to use sets as he'll------"fertilize------" biodiversity immediately at all stages of its development.

    It will make it stronger, more productive biodiversity and allow him to better defend themselves against harmful attacks.

    There is nothing better on the market

    1 Comment

  12. I have written many times that there are systems that : - purify the waste water and direct them for irrigation, while very low rates, because of the small energy consumption is only 0.5 kW per 1 m3. WE INVITE YOU TO SEE THIS MARVELOUS EQUIPMENT IN ACTION.

    1 Comment

  13. We have a Solar Powered Constant / Continuous Move Pivot Irrigator, covering maximum of 75 Acers. The drive is independent of Power. Constant Move makes the machine move in straight line, avoiding frequent start / stops improving water distribution efficiency, and life of the machine. This may be very useful for Africa.

    3 Comments

  14. Centre Pivot designs are generally very similar these days. The major factors to look at are your nozzle/spray package choice and the sizing of the pipes of the pivot. nozzles spread the water to allow for soil infiltration and water distribution. Pivot pipes largely determine energy consumption at your pump (friction losses increase energy consumption with smaller pipes). The better nozzles/sprayers usually cost a little more (think i-Wob) as do the larger pipe sizes to minimise friction losses. A good choice for Africa is the South African made Senter360. DM me if you want contact details for their MD.

  15. Your question is very general. Irrigation design depends on many factors including : water availability, scales (small or large ), weather condition, crop type , and soil type ....

    If you have a large scale, center pivot is best option provided you consider the balance between the irrigation discharge rate and the soil infiltration . 

    2 Comments