CRF products: a smart solution for sustainable farmers

Although it seems to be simple it is easier said than done. However, controlled-release fertilizers (CRF) are products enabling farmers to reach this perfection.

By the ISO standard definition, a CRF is a „fertilizer in which nutrient release is controlled, meeting the stated release rate of a nutrient and the state release time at a specified temperature.“ CRF products are coated with a membrane enabling consistent and predictable release of nutrients largely based on the soil temperature. These features bring farmers several benefits including:

• Fewer applications and lesser nutrient losses resulting in increased nutrient use efficiency (NUE)
• Reduced impact on soil pH and salt content
• Positive effect on soil microbiome
• Reduced carbon footprint at farm level

ICL has been a pioneer in the CRF technology for almost 60 years now, having recently introduced a new generation of biodegradable coatings which meet the new EU regulation. Ronald Clemens, ICL’s Marketing & Portfolio Manager for CRF products, gave an interview for the September-October issue of the Fertilizer International magazine (FI 522, 2024) speaking mainly about the ICL’s patented innovation – eqo.x coating and the new trends and opportunities which can move CRF products on a next level.

Clemens explains: “The mechanism of nutrient release from CRFs depends on the type of coating, but generally it is a very similar combination of diffusion with osmotic pressure. As soon as granules are applied to the soil, water penetrates the coating by diffusion and the nutrients start to dissolve. Osmotic pressure will then slowly press nutrients out of the coating. The coating really needs to work as a membrane, as a kind of raincoat around the granule, for this specific mechanism to work.”

Reduced nitrogen losses mean better NUE

Having fully tested the new biodegradable coating in the field with excellent results, ICL started to utilize it in its well-known and widely used specialty agriculture products Agrocote and Agromaster. CRFs have been proven to be an efficient tool to reduce nitrogen losses with three different mechanisms – leaching, nitrous oxide emissions and ammonia volatilization.

“Comparing standard urea applications with different types of enhanced efficiency fertilizer (EEF), including urease inhibitors, nitrification inhibitors and controlled-release fertilizers, CRFs proved to be actually the only EEF effective at reducing nitrogen losses for all the possible pathways – ammonia volatilization, leaching and N₂O emissions“, Clemens quotes the results of a meta-analysis of 21 previously published studies performed by Australian researchers¹.

Reduced nitrogen losses have one big effect: more of the nutrient remains available for the plant uptake thus increasing the overall efficiency of the applied nutrition. It results in increased yields with the same inputs or allows for reducing the inputs and maintaining the same yields. Be it anyway, the farmer is the one who gains in this case.

Caring for the soil and plant health

Mineral fertilizers are generally perceived as negative agents for the soil health, however might the opposite also be true? Ronald Clemens comments the findings of a long-term study on the effect of CRFs on plant-growth promoting microorganisms (PGPMs) recently published by Chinese researchers²: “The important conclusions were that compared to conventional urea, controlled-release fertilizers were able to increase soil organic matter. The sulfur coated urea (SCU) and polymer sulfur coated urea (PSCU) clearly had benefits in stimulating plant growth and promoting microorganisms, while, on the other hand, inhibiting the growth of nitro and denitrifying bacteria and also reducing plant pathogens.”

Similar positive effects on plant health have been also recently confirmed by research at the Wageningen University in Netherlands supported by ICL. CRFs applied on Pelargonium positively influenced plant’s microbiome, suppressing unwanted plant pathogens. The excess of nitrogen increases plants’ sensitivity to bacterial diseases. However, if the release of nitrogen is controlled (as in CRFs), this danger is reduced.

“This recent study on ornamental plants in the Netherlands, which ICL contributed to, showed that controlled-release fertilizers have a positive effect on the biological control of certain bacterial plant diseases. The main conclusion was that abundant direct nitrogen supply resulted in a higher sensitivity of plants to diseases – and that the type of fertilizers and their applied dose really have an effect on the success of flower growing,” adds Clemens.

Lower carbon footprint for every farm

The correct calculation of a farm’s carbon footprint is a complex process. Taking into account the fertilizer production footprints alone might be misleading. It is always necessary to assess the whole life cycle. Although coated urea has a higher carbon footprint than the conventional product, the higher NUE and reduced nitrogen losses make up for it and the effect on the final carbon footprint figures might be huge.

Ronald Clemens explains: “This is where enhanced efficiency fertilizers like CRFs can really deliver an improvement. For instance, by making it possible to reduce inputs by 20-30 percent – or keep inputs the same and increase crop yields – reductions in the carbon footprint of 10-15 percent are possible over the total life cycle.”

Smart solution for smart farmers

Controlled-release fertilizers are not just modern fertilizers that improve nutrient use efficiency and reduce nitrogen losses and farms’ carbon footprints. They are also a platform for future research and development to enhance fertilizer effectivity, improve plant and soil health and contribute to the sustainability of the whole farming industry.

„Coatings based on sulfur, for instance, can certainly have a positive effect by depressing plant pathogens. I think there are also real opportunities for developing combinations of controlled-release fertilizers and certain biostimulants based on micro-organisms to improve fertilization efficiency,” Clemens concludes for the Fertilizer International magazine.

References:

1. Lam, S., et al., 2022. Next-generation enhanced-efficiency fertilizers for sustained food security. Nature Food, 3, 575-580.
2. Feng, G., et al., 2023. The effect of long-term controlled-release urea application on the relative abundances of plant growth-promoting microorganisms. European Journal of Agronomy, 151, 126971.