Controlled release fertilizers (CRF)

The key to Precision Nutrition

What Are Controlled Release Fertilisers?

Traditionally crop nutrients are applied on a few occasions in a growing season; whereas, crops actually take up nutrients a little at a time hour by hour and day by day.

Early in the season as small annual crops establish, or as perennial crops emerge from winter dormancy, uptake is quite small each day. Many fertilisers are soluble and volatile, so applied early in the season large amounts of nutrients are available – far more than the crop’s immediate need.

Controlled release fertilisers (CRF) provide nutrition that closely matches the plant requirements so little is lost and the crop can maximise nutrient uptake.

What distinguishes Controlled Release from Conventional Fertilisers?

Conventional fertilisers dissolve in the soil immediately after application, only providing nutrition for a short period of time. Multiple fertilizer applications are necessary to ensure that your crop gets the nutrition it needs. Multiple applications can also be practically complex for big farms, costly, and, as we know from recent studies, increase problems with soil compaction.

Thanks to their special coatings, CRF granules release their nutrients gradually over an extended time. Depending on a CRF product’s longevity, nutrient release takes several weeks up to many months.

For conventional fertilisers applied to major cereal crops, nitrogen efficiency is around 40-65 percent, potassium efficiency in the region of 30-50 percent and phosphorus efficiency just 15-25 percent. CRF is considered the fertiliser technology with the highest nutrient use efficiency and in many cases seeing an increase of over 50%.

What differentiates Slow and Controlled Release Fertilisers?

Both supply nutrients to the plant gradually, however, CRF uses advanced technology and a unique coating, so the release of nutrients is controlled and designed to closely match the need of the plant at a specific temperature.

Slow-release fertilisers (SRF) provide nutrient availability to plants spread over a period of time, but this is not controlled and is dependent on factors such as hydrolysis, biodegradation or limited solubility.  

So, the nutrient release mechanism for the two fertilisers is completely different. SRFs are minerals that take a certain time to dissolve or release their nutrients. CRFs require a good quality coating and a consistent manufacturing process. While SRFs nutrient release is influenced by temperature, water, soil pH, and micro-organisms, CRFs are only influenced by temperature and water.

How long do Controlled Release Fertilizers continue to release nutrients?

At higher temperatures, the release of nutrients will be faster. At lower temperatures, it will be slower, in line with the nutritional needs of the plant. ICL Fertilizers produce a range of blends and can tailor the contents of each fertiliser to the needs of specific crops.

How do Controlled Release Fertilisers work?

The fertiliser is covered in a special coating that, once in contact with the soil and associated moisture, begins to take up water. As the moisture content builds up in each granule of fertiliser, the osmotic pressure increases and nutrients start to ‘escape’ into the soil via micropores in the coating.

Thus the nutrients disperse gradually into the zone around the roots and are available as the plant requires them. This minimises the risk of valuable nutrients being lost from the crop and ending up causing adverse effects to air or water.

A good Controlled Release Fertiliser is determined by the quality of the coating. At ICL we use our extensive experience in coating to create products with an accurate release time in order to fulfil the product promises.

What are the most common uses for controlled release fertilisers?

Controlled release fertilisers can be used for many different crops such as field vegetables, top fruit and forestry including plant-hole and row application.

How do controlled release fertilisers help the environment?

For more information, visit our CRF Knowledge Hub here


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