| When you buy a bag of fertilizer, it usually has a set of numbers that look something like this; '10-5-15' or '10-10-10'. These numbers represent the levels of major nutrients contained in the fertilizer represented as 'N-P-K' or 'Nitrogen-Phosphorus-Potassium'. Nitrogen (N) percentage is the first number. This is a primary nutrient that makes the plant grow. Phosphorus (P) percentage is the middle number. This is a primary nutrient that encourages rooting, blooming and fruit production. Potassium (K) percentage is the last number on the bag. Potassium helps plants to resist disease and aids in hardiness. Kim, from WA, entered 1999-12-16 | 