In the Lensli Academy we regularly inform you about practical situations that we encounter in the sector, we talk about insights gained in practice, we give you cultivation tips and we share our knowledge about other interesting substrate-related matters.
Academy – Slow release fertilizers
Fertilizers: a wide range of possibilities
Fertilizers are necessary for healthy and strong crops and come in many different forms, from single to multiple applications and from slow-acting versus fast-acting variants. But what determines which variant and strategy is most suitable for your crop? Every nursery, cultivation and plant is different and based on, among other things, the fertilization strategy, company objectives and wishes, we determine together with the customer which type of fertilizers are used.
Basic fertilizers
We traditionally use fast-acting, simple basic fertilizers, both in organic and artificial form. These variants offer growers a quick, but also short-term solution for their crop. The fertilizers are absorbed and fully used in a short time, which means that adjustments must be made at several points during the cultivation. To give the cultivation a good start, we often start with a high EC value, so that the fertilizers can be controlled better during the course of the cultivation. The disadvantage of this is that nutrients are not always available to the plant in the correct proportions. This can cause a plant to grow too quickly or become more susceptible to diseases and pests.
The disadvantage for a grower of using regular, fast-acting fertilizers is that this is a time-intensive way of working, requiring adjustments to the fertilization at various times. This form of fertilization does offer the advantage of being able to adjust at element level; However, this form of fertilization takes a lot of time and energy. Often many more fertilizers are required than with slow-acting solutions.
Slow release fertilizers
By using slow-release fertilizers, the substrate not only contains the correct nutritional balance at the start of cultivation, but also during cultivation. Slow-release fertilizers are, as it were, a nutrient buffer during cultivation; the fertilizers are constantly present in the substrate, so that a plant always has access to the right nutrition.
Naturally, a grower still needs to monitor how the cultivation is progressing and make adjustments where necessary, but compared to the regular fertilization strategy, this is much less necessary. Particularly in certain situations where rain plays a major variable role, as is the case with open cultivation, nutrients that are available for longer periods of time are important.
The use of slow-release fertilizers offers a grower convenience, security and efficiency. Thanks to the slow-acting fertilizers, much less control is required during cultivation, which relieves the grower's burden.
The use of slow-release fertilizers in combination with basic fertilizers
A grower often wants a maximum EC at the start of a cultivation, or this is necessary for a specific cultivation. In order not to start with an EC value that is too high in these types of situations, we recommend slow-release fertilizers in addition to the use of basic fertilizers.
As an example: A green plant grower uses a peat-free mixture, with relatively high nitrogen fixation. There is limited possibility to steer this with the A+B gearbox. With water-soluble fertilizers such as lime nitrate, the starting EC is too high. In this situation, a coated fertilizer (CRF) with different operating times can be chosen, or an SRF with an operating time between 2 and 4 months.
Different types of slow release fertilizers
The slow-acting fertilizers can, just like the basic fertilizers, be divided into Organic and Artificial fertilizers:
- Organic fertilizers
Consist of at least 60% organic material
Create a correct nutritional environment based on animal or vegetable bacteria
Effective for up to 100 days
Release is partly dependent on soil life - Artificial fertilizers
SRF (Slow Release Fertilizer)
Releases nutrients gradually
Performance less predictable and reliable than coated fertilizers
For example Crotodur
Effective for 2-4 months
CRF (Controlled Release Fertilizer)
Coated fertilizers
Thanks to the coating, the fertilizers are released slowly, making it easier to regulate the growth of the plant.
Osmocote – Multicote
2 – 16 months active
Advantages of slow-release fertilizers
The most important advantages of slow-release fertilizers compared to regular fertilizers are:
- The fertilizers are continuously present in the substrate and therefore in the pot.
- Offers a grower convenience during cultivation and fertilization
- Much less error-prone compared to other fertilization strategies
Overall, the SRF and CRF fertilizers offer the grower a certain degree of safety and security: after all, a plant has access to the right nutrients it requires for a longer period of time. The effect of organic slow-release fertilizers depends on the quality of soil life, which is less easy to control.
Renewable raw materials
With the use of more and more renewable raw materials in substrates, we are faced with different interactions than we are used to with peat-containing substrates, and the use of slow-release fertilizers is becoming increasingly important.
For example, many raw materials in low-peat and peat-free compositions have a lower buffer, withdraw nitrogen from the nutrient solution or bring nutrients with them. Consider, for example, compost, wood fiber, bark products, coconut and the Basic BioMix. As a substrate producer, we can overcome these situations and create the right balance in the substrate by using different types of fertilizers.
Consult with your Lensli account manager or product manager about what is the best choice for you, to ensure that the peat-free substrate you use is in balance with the desired cultivation and fertilization strategy.
Would you like to know more about the possibilities for your own cultivation, do you need a sparring partner or do you have another substantive question? Please contact your Lensli account manager or our Substrates Technical Product Manager Nick Vollmer by email n.vollmer@lensli.com or telephone +31 (6) 51269415.
We are happy to talk to you.