The logic behind the introduction of slow-release fertilizers lies in the need to regulate the supply of Nitrogen which is a highly soluble element.  Urea Formalde-hyde polymers are the most important ingredient  of slow-release fertilizers.  Availability of nitrogen is controlled by microbial activity which in turn is controlled by temperature.  Culterra's range of SRN's is available in 2kg, 5kg, 10kg and 20kg bags.

Available -

Vitaflora 5.1.5 SRN

Vitaflora 2.3.2 SRN

Vitaflora 3.1.5 SRN

Vitaflora 3.2.1 SRN