NPK is important because they work synergistically to help your plants grow better than any single component would alone. When we add just 1 or 2 nutrients to our garden, chances are there will be no visible results. However, when we combine all 3 of them, we get a much stronger effect. The NPK value represents different percentages of each nutrient present in the mixture. The ideal NPK ratio will depend on what you are growing as different plants need different amounts of nutrients.