Next Generation Controlled Release Fertilizer (NextGenCRF)

NextGenRnD® Solution No. 19

General description of the NextGenCRF approach

According to the European Standardization Committee (CEN) Task Force on Slow-Release Fertilizers1, the criteria of controlled release fertilizer (CRF), which releases the nutrients slower than conventional fertilizer, are as follows: (i) < 15% of the nutrients (e.g., urea) are released within 24 hours; (ii) < 75% of the nutrients are released within 28 days; and (iii) > 75% of the nutrients are released within the stated release time.

The report2 by Lawrencia et al. evaluated various materials and their modifications with respect to the “< 75% of nutrients release within 28 days”-criterion of CRF and reached the following conclusions. First, sulfur and mineral(inorganic)-based CRFs do not satisfy this criterion. Second, among the synthetic polymer-based CRFs: polystyrene-, polyurethane(PU)-, and polyvinyl alcohol(PVA)-modified materials satisfy the criterion with only the PVA-based material being biodegradable. Third, of natural polymer-based CRFs: bio-based PU, poly(eugenol sulfone), latex, starch, cellulose, and alginate modified materials release less than 75% of nutrients within 28 days. Furthermore, Lawrencia and colleagues found that the CRFs that fulfilled the criterion (ii), mentioned above, combined both hydrophilic and hydrophobic materials. Therefore, authors concluded that the “ideal” CRF should enable efficient adsorption of nutrients to its matrix and should be composed of both hydrophilic and hydrophobic materials.

Synthetic polymers, including thermoset resins (e.g., urethane-, epoxy-, unsaturated polyester-, phenol-, melamine-, and silicon-based), are mostly non-biodegradable, which leads to their accumulation in the soil, non-optimal crop yield, and concomitant damage to the soil and to the environment. Thus, nowadays, there is a pressing need for the natural polymer-based CRFs.


An optimal natural polymer-based CRF (“ONP-CRF”) would have the potential to not only provide the nutrient controlled release functionality, but would also enable water retention, pH correction, and an additional source of nutrients among other essential requirements according to the European Standardization Committee (CEN) Task Force on Slow-Release Fertilizers. In this NextGenCRF Solution, NextGenRnD describes the experimental approach allowing the determination of the materials sufficiently characterized and enabling such functionalities.

The major current technical approach is to have a fertilizer, e.g., urea, as a core granule and to cover it with either a single or multiple polymer layers, which are preferably biodegradable. In contrast, to create ONP-CRF capsules, the NextGenCRF platform offers to cover urea micro prill with either a single fully-biodegradable polymer layer of variable thickness or multiple fully-biodegradable polymer layers. The inventive step (non-obviousness) is the combination of the urea micro prill and coating with a specific hybrid polymer composition. Specifically, fully biodegradable hybrid three-component polymer is proposed.

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