Secondary Nutrient 
The macro-nutrients of Calcium, Magnesium and Sulphur. Sodium is also classed as a secondary nutrient in the Fertilisers Regulations 1991, however, this for its benefit to agricultural animals and not turfgrasses.
Secondary Nutrient
The macro-nutrients of Calcium, Magnesium and Sulphur. Sodium is also classed as a secondary nutrient in the Fertilisers Regulations 1991, however, this for its benefit to agricultural animals and not turfgrasses.