Tools & Tips

Fertilizers Mixing Rules

Irrigation Water quality

Fertilizers Information

Plant Nutrition

Growing Media & Hydroponics

Technical

7. Many labs express the Calcium, Magnesium and alkalinity as CaCO₃.

    To convert from Ca as CaCO₃ to Ca - multiply by 0.4.

    To convert from Mg as CaCO₃ to Mg - multiply by 0.24.

    To convert from HCO₃^-  as CaCO₃ (alkalinity) to HCO₃^- - multiply by 1.22 (for pH <8.4).

Fertilizers Data

1. Solubilities of common fertilizers are presented in the following table:  

 2. The fertilizer label refers to how much of an element is in the fertilizer, based on

    percentage by weight. All fertilizers are labeld by three numbers which indicate the

    percentage by weight of the three main elements - nitrogen, phosphorus and

    potassium. The first number refers to the total nitrogen, the second number to the

    oxide form of phosphorus (P₂O₅) and the third number refers to the oxide form of

    potassium (K₂O).

    The amount of micro-nutrients (like iron, manganese, zinc etc), if present in the

    fertilizer, is usually indicated in ppm - parts per million.

3.  Common fertilizer and their formulas:
    
     Ammonium Sulphate    (NH₄)₂SO₄

       Calcium Nitrate            5Ca(NO₃)₂ + NH₄NO₃*10H₂O

     Magnesium Nitrate       Mg(NO₃)₂*6H₂O

     Potassium Chloride      KCl

     Agricultural Lime          CaSO₄*2H₂O

     MAP (12-61-0)             NH₄H₂PO₄

       M.K.P (0-34-52)           KH₂PO₄

     Phosphoric acid           H₃PO₄    

  
4. What is Lime? Lime is a suitable material added to raise soil pH. Its application to

    acidic soils improves crop response of many crops.

    Common liming materials are ground limestone, ground dolomitic limestone, burned

    lime and hydrated lime.

    Factors that determine the liming material efficiency are:

• The physical particle size - fine particles are much more effective than medium or
  coarse particles.
• The chemical guarantee - equivalent to the impure whole material.

    The product of both chemical and physical properties is the neutralization index.

 Plant Nutrition

1. The NH4/NO3 (Ammonium/Nitrate) ratio affects the growing media pH when growing in

    containers. In higher ratio, the pH in the growing media may drop. The reason is that the plant

    roots relase hydrogen ions when uptaking NH4 (NH4 has a positive charge, like the hydrogen

    ion).

 2. Yield response curve: The curve below describes the crop response to fertilizers application -

    Zone A - Too low fertilizers application which results in nutrient deficiencies and lower yields

    Zone B - Adequate fertilizers application results in maximum efficiency and the highest

                 profitability.

    Zone C - Over fertilization where yield is not affected but fertilizers are wasted.

    Zone D - Excessive fertilizers application which results in decreased yields, toxicities and

                 salinity damages

Growing Media And Hydroponics

1. Analyzing dripper and drain water is extremely important in growing media, in order to

   monitor irrigation and fertilization. Basic analysis includes: pH, EC, drainage % out of the

   irrigation water.

   Nevertheless, these tests are not always enough. In case of non-uniform wetting of the

   medium may elicit false results in the drainage tests. The more porous the medium, the higher

   the chance of getting false results under non-uniform wetting conditions. Water will drain   

   through the larger pores, gravitating down ducts without washing out the salts.

   The drainage EC    test will indicate reasonable levels, but in reality salts are accumulating in  
   the medium. The solution is to do a visual check, e.g. turn the container upside down, and
   make sure wetting is uniform. While holding the container upside down, look also at the  
   distribution and density of the root system. It indicates if your irrigation regime is adequate and
   if the medium complies with the system's specifications. A whitish root system, well branched 

   and with visible root-hairs, is a healthy system.

 
2. How can you know if salts accumulate in the medium? Wash the container medium using a

    garden hose nozzle, or with a beaker. That way the medium will be saturated.

    Use the same water as the irrigation water (otherwise you'll have to calculate the difference).

    Wash only until you get the same drainage quantity as during regular irrigation (because the

    salts concentration in drainage water depends on the volume).

    If the EC in your regular drainage is significantly higher than the EC in your "wash" drainage,

    that means your medium accumulates salts on the edges.

Technical

1. Accurate fertilization starts with calibrating your system. Make sure it indicates the actual

    flows and volumes.

    Check your:

• Water Counters
• Fertilizer counters
• EC sensor
• pH sensor

2. Checklist for planning an efficient fertigation system

    If you are in the planning phase of a fertigation system, use this check list to make sure your 
    system can live up to your requirements:

• Determine the content and concentrations of the fertilizers solutions to be used
• Determine the required fertilization level, including pH, EC and injection rates
• Determine the required irrigation flow rate
• Calculate the minimal injector flow rate required, using the following formula: maximum irrigation flow rate x minimum required injector rate.

For more information read the articles How to choose the right fertilizer injectors and How to calibrate and test your fertilizer injectors