Why proven Controlled Release Nutrition sets the standard

Andrew Wilson, ICL technical manager for the UK and Ireland, looks at how traditional simple organic fertilisers compare with the market leading Osmocote controlled release fertiliser range. He recommends growers look beyond the price as differences in formulation, reliability of nutrient release patterns and recommended rates all influence the true cost of nutrition in ornamental crops.  So, are these simple organic fertilisers worth the risk?

Developed over more than 50 years, Osmocote remains the gold standard in controlled release fertiliser (CRF) for ornamental nurseries worldwide. As substrates and production systems have evolved, so too has this pioneering range, with substantial R&D investment ensuring it continues to meet the needs of modern growers. The latest fifth-generation Osmocote 5 range has been specifically developed to optimise nutrition in sustainable peat-reduced and peat-free growing media.

Nutrient use efficiency in Controlled Release Fertilisers

Quality controlled release fertilisers deliver exceptionally high nutrient use efficiency (NUE), minimising nutrient losses to the environment while providing a consistent, predictable nutrient supply. Nutrient release from Osmocote granules is governed by the coating technology, thickness and temperature. Decades of research have enabled ICL to develop products with different longevities, precisely matching nutrient release to crop demand throughout the growing cycle. Every granule contains a balanced package of NPK and trace elements, ensuring uniform nutrition and consistent crop performance.

How Organic and Controlled Release Fertilisers differ

Organic fertilisers work very differently. Traditionally developed for soil-based agricultural systems, producing low value combinable crops, simple organic fertilisers rely on microbial activity to break down organic matter to make nutrients available to the plants. The speed of nutrient release depends on factors including temperature, moisture and pH, making it inherently less predictable. Wet conditions can accelerate nutrient release, while cool or dry conditions may slow it significantly.

This becomes even more relevant in modern ornamental growing media. While peat naturally supports biological activity, many widely used peat alternatives contain very little. Sterilised woodfibre and coir, now common components of quality UK growing media, are virtually free of microbes, while bark provides limited biological activity. Although some continental growing media incorporate green compost, which supports greater microbial populations, it is not considered a mainstream quality peat-alternative in the UK or Ireland.

So, nutrient release from organic fertilisers remains dependent on biological processes that growers cannot easily control.

It is worth noting that when topdressing with organic fertilisers there is the potential for volatilisation – where the nitrogen component is lost to the air as ammonia gas.  An issue neatly addressed with our advanced Poly-S coating for Osmocote Topdress FT.

Comparing the true cost of Fertiliser

Although simple organic fertilisers may appear attractive on upfront cost, it is important to look beyond the purchase price.

Major differences in the formula, nutrient availability and recommended application rates all influence the true cost of nutrition. With nitrogen bound within organic matter, potassium readily water soluble and phosphate often slow to become available, nutrient release patterns can be highly inconsistent, increasing the risk of variable crop performance and the need for corrective feeding.

Reliable nutrition and technical support for nurseries

By contrast, incorporating Osmocote into the growing media mix at manufacture provides confidence that the nutrition element is taken care of from the outset.

With Osmocote you get the technical support as well as the proven performance professional growers need.  Nursery production teams benefit from the support of ICL’s FACTS-qualified Technical Area Sales Managers plus AngelaWeb3.0 – our precision nutrition software that creates custom fertiliser and crop nutrition plans.

The future of Osmocote Controlled Release Fertiliser

With EU Fertilising Products Regulation (FPR) requirements for biodegradable coatings approaching, ICL is continuing to invest heavily in the future of its controlled release fertilisers. During 2026 alone, 240 trials are underway across Europe, including 23 in the UK and Ireland, evaluating new biodegradable Osmocote coating technologies.

It is this continuous commitment to innovation, combined with nearly six decades of proven reliability, that keeps Osmocote the controlled release fertiliser trusted by professional growers worldwide.