Fertigation

With fertigation diluted fertilisers are given with the irrigation water.

The advantages of this system are:

  • Fertilizers can be given in the correct ratios and concentrations.
  • Small concentrations of fertilizers can be applied frequently.
  • The nutrient status can be kept near the optimum value permanently.
  • The nutrient status can be adjusted according the growth phase and needs of the plants.
  • Fertilizers move with the irrigation water into the soil and are therefore spread more evenly than in the case where granular fertilizers are broadcasted on the soil surface by hand.

With the A and B – tank system stock solutions of fertilizers are dissolved in two tanks called the A and B – tank. The size of each of these tanks is normally 1000 litre and the concentration of the stock solution in each tank is 10% (100kg of fertilizers in each tank). Fertilizers are injected from these tanks into the mainline of the irrigation system. The amount of fertilizers injected from the concentrated tanks is controlled with an automatic electric conductivity meter (EC – meter). This instrument measures the conductivity (EC) of the irrigation water in the units mS cm-1. The EC is a function of the total amount of salts in the water and regulation of the EC is therefore an accurate way to regulates the amount of fertilizers in the irrigation water.

The garden: The A and B tank system is however too complicated and expensive to use in gardens. A less expensive alternative is to make a ready to use mix of fertilisers in a big tank (between 1000 and 5000 liters) and to irrigate your garden once a week directly from this tank. The following mix may be used as long as the quality of your irrigation water is good.

Add the following fertilizers once a week per 1000 liters of irrigation water:

Sandy soils:

200 gram calsiumnitrate + 250 gram potassiumnitrate + 20 gram mono ammonium phospate + 100 gram magnesiumsulphate.

Clay soils:

150 gram calsiumnitrate + 200 gram potassiumnitrate + 20 gram mono ammonium phospate + 100 gram magnesiumsulphate.

Warning: If the above mix is not properly diluted unwanted chemical reactions will take place (Example: the calcium in the calcium nitrate will react with the sulphate in the magnesiumsulphate and insoluble gypsum will be formed). For the prevention of unwanted reactions use the following procedures:

1. Fill the tank to the 1000 liter mark.

2. Add the CaNO3 and stir.

3. Add the KNO3 and stir.

4. Add the MgSO4 and stir.

5. Add the MAP and stir.

Warning: Do not use a stronger concentration unless otherwise advised by a soil scientist.

Give once a month a foliar spray with a foliar feed containing all the trace elements.

Please note that this fertigation program does not take the nutrient status of the soil into consideration. For the calculation of an accurate program an analysis of the soil and the clean irrigation water is needed.