Controlled-release fertilizers in horticultural production
The aim of this article is to inform our readers – growers and other interested professionals – about the potential drawbacks of using controlled-release nutrient fertilizers (so-called CRF fertilizers) in professional horticultural production. They are becoming more and more popular and growers have learned to love them regardless the size of their business.
The advantage lies especially in the simple application and in the excellent results achieved.
Composition of the slow-release nutrients
These products are based on standard chloride-free granulated mineral fertilizers of accurately targeted fractions combined with a concentrate of microelements, most of them in chelate form. The surface of the granules is covered in a semi-permeable membrane (envelope). Different producers choose different materials according to their know-how.
The ratio of essential nutrients – N, P, K is designed upon the customers’ preferences, or upon the specific needs of the cultivated crops. These fertilizers can be used for almost all plant species, there are no big differences.
Easy to use
The controlled-release fertilizers, as their name suggests, supply nutrients for months, compared to standard fertilizers that only last for weeks. The actual application is very simple – the fertilizer is mixed in with the substrate during its production, or it can be added by the grower shortly before planting. The defined amount of fertilizer can be also placed underneath the plant inside the pot (dibbling method). The recommended dose per unit or area or volume of substrate is stated in the instructions for use. It usually ranges around 3 grams per litre of substrate.
Advantages of controlled-release fertilizers
High concentration of nutrients, the form of solid dust-free granules supplied in 25 kg bags makes these fertilizers easy to store, even in non-air-conditioned areas. The gradual intake of the nutrients by plants depends on the temperature around the roots, and is almost immediate with minimum loss. If mixing the fertilizer in with the substrate the dosage is very accurate thanks to an automated production process.
Limitation of use
The impossibility to use these fertilizers in usual doses during high summer temperatures, especially in covered areas, can be limiting in some cases. In outdoor areas, on the other hand, nutrient release slows down under the ideal needs of the plants if temperatures are too low. A check-up of the plants’ real nutrition condition should be carried out in the second half of the growing season, and followed by a potential remediation of any deficiencies.
Controlled-release fertilizers are a significant factor in the intensification of horticultural production. Their application is very easy, quick and effective with correctly recommended dosage, and can be performed just once per growing season. This prevents the occurrence of necrosis or other damage to the leaf. Slow-release fertilizers effectively address the current need of individual nutrients, and also eliminate other omissions during the technological procedure of plant cultivation.
The results are highly successful if all other technological requirements of plant growing are met.
Ing. Jiří Valtera, AGRO CS