Overview NPK 21:5:10 is a high-nitrogen complex fertilizer where the guaranteed nutrients (by weight) are: N = 21% P₂O₅ = 5% K₂O = 10% “Complex/compound” generally means each granule contains N, P and K (made by chemical reaction + granulation, or by granulating a blended mix), rather than a simple physical blend of separate single-nutrient […]
