"NPK" stands for Nitrogen, Phosphorus, Potassium.
Nitrogen: encourages foliage growth.
Phosphorous: encourages root and flower growth.
2 letters - ph ("f") - flowers/roots
Potassium - Pest resistance
Do plants only need nitrogen, phosphorous and potassium?
No. Feeding plants artificial fertilizers that only contain N-P-K is like raising your kids on a diet of white bread and soda. They will grow, but they will not be healthy. They need more.
“Up, Down and All-Around” is another way to think about NPK and the numbering system for fertilizers. Your lawn needs nitrogen for the leaves’ color and growth, phosphorous for strong roots, and potassium for overall health. Source: Home Depot.
My 7 Most Important Organic Soil Amendments | http://bit.ly/YjPIa4
Why The N-P-K Is D-U-M(b) | http://bit.ly/YjPPSO