Nitrogen is.
The first element in the fourth period, which is used in making fertilizer, is potassium.
Nitrogen.
potassium
This chemical element is potassium (K).
Potassium
Phosphate fertilizer is a compound, not an element. The compound contains phosphorus.
Potassium is the element that used to be first to make fertilizer.
Nitrogen.
Nitrogen.
nitrogen
gypsum
Sulfur