Controlled Release Fertilizers vs Slow Release Fertilizer

A common misconception is that Slow Release Fertilizers (SRF) and Controlled Release Fertilizers (CRF) are the same. Both deliver nutrients over a duration but are completely different products.

Controlled release fertilizers are affected by only one factor that is soil temperature and therefore releases plant nutrients at a predictable and sustained rate. Controlled release fertilizers only come in the granular form where the coating thickness regulates the nutrient release.

Slow Release Fertilizers, on the other hand, are affected by soil temperature, moisture, microorganisms, surface area and pH. Slow Release Fertilizers come in granular, nugget or packet/sachet forms where the release mechanism varies widely.

The table below compares the different types of Slow Release Fertilizer and Controlled Release Fertilizers on the market.


Table Comparison of Controlled vs Slow Release Fertilizer

CharacteristicSK Cote CRF SCUIBDU/MU/UF NuggetInhibitors
TechnologyPolymer CoatingSulphur Coating Urea Reaction Product CompressionNitrification/Urease Inhibition
Release MechanismDiffusionRupture of coatingIBDU: Hydrolysis

MU/UF: Microbial activity
Smaller surface area Inhibition of enzymes
Longevity2-24 months 2-3 monthsIBDU: 90 days

MU: 12 weeks

UF: 12 weeks
2-4 months Depends on soil moisture and bacteria
Release Controlling FactorTemperatureMicrobial activity, moisture, temperature.Microbial activity, moisture, temperature, pH, organic matter.Microbial activity, moisture, temperature, pH. Microbial activity, moisture, temperature, pH.
Controlled Release100% 40-50%20-85%30-50% 0

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