An Introduction to Controlled-Release Fertilizers

Coated or controlled-release fertilizers (CRF) have become increasingly popular and have gathered a great deal of attention from growers and agronomists around the world. Applying lower amounts of fertilizer is one solution to dealing with new regulations limiting the amount of leached nitrogen. Scientific proof has shown that growers can achieve the goal of higher production and higher quality with coated fertilizers. These fertilizers achieve results that are at least as good as standard fertilization while using less fertilizer, sometimes up to 25% less, with the benefit of leaching fewer nutrients and requiring fewer application passes. CRFs are used in all agricultural and horticultural crops all over the world. Each application in a particular climate calls for a specific fertilization strategy. Due to the differing length of time that each CRF granule takes to release the nutrients inside, it is possible to fertilize on cycles as short as 6 weeks and as long as 18 months. CRFs are fertilizers with one or more primary macro-, meso-, or micronutrients in a coated granule. There are different types of coating which gradually release the nutrients. Blends are often produced to achieve the correct nutrient levels for every crop. There is a wide range of available products from 100% coated NPK with trace elements to partially coated blends (N and/or P and/or K) with, or without, trace elements.  

The Special CRF Coating

These are all CRF products! However, the most important part of a CRF is the coating itself. The difference in coating percentages affects the direct availability of nutrients to the plant as well as leaching during the growing season. The type of coating is also important, whether it is a resin coating, a sulfate coating with a higher initial release, or a coating of polymer (polyethylene). Each coating technology has its own specific characteristics. Factors influencing the release of nutrients are moisture content and soil temperature. In resin or sulfate coatings, the release mechanism is primarily determined by the thickness of the coating. Coated products are also available which allow the microbiology within the soil to affect the release pattern. During the production process, the choice of nutrients combined with the type of coating are the key factors in the release of macro- and micronutrients. If this combination is not correct, not all of the macronutrients (especially the microelements) will be released. If the nutrients remain in the granule, they cannot benefit the plant.    

What are the Advantages of CRFs?

For the best results, choose a CRF to meet the needs of a particular crop taking into account soil type, temperature, and cultivation method. Also consider how the individual elements are released as well as the CRF’s period of effectiveness. For example, autumn leeks have a different requirement to winter leeks.

• There is better plant growth due to the continuous and uniform availability of the nutrients.
• Fertilizer application can be reduced by 20-25% as the risk of leaching is minimal. Of course, even with a CRF, rain will wash away the minerals which are present in the root environment, but the CRF will immediately release new nutrients.
• The positive effects of CRF application can include higher yields, better quality distribution, more uniform grading, a larger tuber, and greater plant weight. Because the plant grows evenly and gradually, it is less susceptible to damage and diseases such as aphids or powdery mildew, and will show fewer deficiencies.

How do you Select the Right CRF?

It can be hard for growers to differentiate between the various CRFs and choose the one that is right for their crop needs, climate needs and, of course, their budget. Perhaps the most important aspect is the efficiency: does the release of nutrients meet the needs of the plant during the whole growing stage? Suppliers of CRF will be able to advise you on specific fertilization questions and in consultation with the producer (ICL, for instance), growers can receive customized advice without obligation. It is even possible to draw up a nutrient release chart over time, per nutrient, taking all the relevant conditions into account. ICL has a very broad portfolio of CRF products e.g., Agroblen®,  Agromaster®, and Agrocote®. These products have different types of coating, differing coating percentages, and different longevities so they can suit a wide range of crops. Our production methods are verified by three different ISO certifications and all products are REACH compliant.