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TESTING YOUR IRRIGATION WATER

The quality and content of the irrigation water can greatly affect the success of your crop.

 

Testing your irrigation water is important for assessing the suitability of the water source for irrigation.

 

Knowing what is in your irrigation water is also essential for the day-to-day practice, affecting both the irrigation regime and fertilizer schedule.

 

WHAT SHOULD YOU TEST FOR?

Most labs will ask you to indicate which tests you would like them to do.

The required tests depend on:

 

  •   The source of water – i.e. surface water, ground water, reclaimed water, desalinated water etc.

     

  •   The irrigation method.

     

    The tests can be divided to three groups: chemical (salt concentration and composition) physical and biological.

     

     

     

    Test

      What to expect
    Surface water Groundwater
     Chemical Low salt concentration  Medium-high salt concentration
     Biological contaminations Very likely to be found   Less likely to be found
     Physical contaminations Very likely to be found  Low level is expected

     

     

    BIOLOGICAL AND PHYSICAL PARAMETERS

    Biological contaminants include algae, bacteria, nematodes and viruses.

     

    Physical parameters - The two main parameters which define the extent of physical contaminations are Turbidity and TSS (Total Suspended Solids).

     

    Read more about physical and biological contaminations in irrigation water.

     

    You will most likely need to test your irrigation water for physical and biological contaminants in the following cases:

     

  •   Your water source is surface water, you are using trickle irrigation and/or you are growing crops that are sensitive to water-borne disease.

     

  •   Your water source is reused water.

     

    CHEMICAL PARAMETERS

    Standard irrigation water testing will usually include the chemical parameters.

    Recommended chemical tests for surface and groundwater:

     

     Element

    Groundwater

    Surface water

    Calcium (Ca)

    Magnesium (Mg)

    Sulphate (SO4)

    Bicarbonates (HCO3)

    Carbonates (CO3)

     

    Sodium (Na)

    Iron (Fe)

     

    Manganese (Mn)

     

    Boron (B)

     

    Fluoride (F).

     

    Nitrate (NO3)

     

    Phosphate (PO4)

     

    Chlorides (Cl)

    Electrical conductivity

    pH

    √ 

     

     

    The chemical quality of your water is important for the following reasons:

     

    1. Determines the suitability of the water for irrigation – your water may have high salinity (high EC), high SAR level or contain harmful elements in levels that might be toxic to your crop. Read more about irrigation water quality.

    2. Affects crop yields – the total salinity of the irrigation water and the level of particular elements can reduce the crop yield, if a certain threshold is exceed. This threshold is crop specific.

    3. Influences the fertilization program – your water may contain essential plant nutrients, like calcium, magnesium, sulphur and boron. Adequate levels of these nutrients in the irrigation water can save on fertilizer use, as nutrients present in the irrigation water are available to the plant.

    4. Affects the irrigation schedule - high salt level in your water may require higher application amounts in order to prevent salts to accumulate in the root zone.

     

    SAMPLING YOUR IRRIGATION WATER

    • Make sure to take a representative sample of your water.

    • Use a plastic or glass container/bottle.

    • For chemical analysis – rinse the container several times with the water you are about to sample.

    • For biological analysis use a sterilized container, provided by your laboratory. Never rinse the bottle prior to collecting the sample.

    • Label the bottle clearly, immediately after sampling.

    • Seal the container properly.

    • Sample must be placed in an ice-cooled chest and delivered to the laboratory as soon as possible. Some parameters are more time sensitive than others. 


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