Preparation of liquid fertiliser stock solutions

Page last updated: Monday, 5 January 2015 - 9:08am

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Liquid fertiliser is commonly used on its own or as a supplement to base fertiliser in horticulture. Although a range of proprietary liquid feeds is available, it is cheaper to mix your own recipe from single nutrients. The formula can be tailored to your specific crop and the ratio of nutrients adjusted to growth stage and time of year.

It is convenient to make up concentrated batches of fertiliser and dilute them through a proportioning device. These batches of concentrated nutrient solution are known as stock solutions.

This web page describes the steps in making up a stock solution.

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Mixing

Fertilisers differ in the amounts that can be dissolved in water. Most fertilisers dissolve more readily in warm or hot water.

When making up concentrated stock solutions it is helpful to know the solubility of the chemicals involved. Some examples are listed in Table 1 below.

Table 1 Solubility of common fertilisers
Fertiliser	Solubility in water @ 20ºC (g/L)
Ammonium nitrate	1902
Ammonium sulphate	750
Boric acid	49
Calcium nitrate	1290
Magnesium sulphate	330
Potassium chloride	340
Potassium nitrate	316
Potassium sulphate	111
Urea	1000

Remember, if a stock solution is heated to dissolve the components, the fertiliser may crystallise when the solution cools down. To avoid this, dilute the solution or use it immediately.

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Preparation of liquid fertiliser stock solutions

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Mixing

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