Be cautious when using slow release fertilizers

Fertilization with slow-release fertilizers has recently caused some damage in horticulture, as reported by Agro Expertiseburo in its newsletter.

Coated slow fertilizers are often used in horticulture. They have a long action period, whereby the fertilizers are supposed to be gradually released over time. However, in a number of damage cases it was found that the release of fertilizers may already be very high in the first period after application. This can cause high EC levels (salinity) in the pot or release too much of a certain fertilizer (for example Ammonium). This can cause damage to young plants that still need to take root. There may also be too little release of nutrition from the slow-release fertilizer at the end of cultivation, which means adding more fertilizer incurring additional costs. In the meantime too much fertilizer is rinsed out, which is bad for the environment.

When choosing a fertilizer it is important to get information about:

- What is the purpose of the fertilization;

- The content of the coated granules and its properties;

- What is released when and under what circumstances;

- How safe is the product in cultivation, first acquire experience by conducting tests;

- Compare the costs and benefits of the fertilizer and consider the environmental impact.

Examination of the crop, substrate and irrigation water provides insight into whether and the extent to which the nutrition presents irregularities. Agro Expertburo can assist you in investigating the cause and establishing the extent of the damage. In these type of damage cases Agro Expertiseburo always collaborates with the laboratories and consultants of the Delft Research Group in Delfgauw.

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