Photo courtesy of eh3k at Flickr.com.
We’ve all seen the mysterious numbers on fertilizer and lawn-food bags (10-2-4, 0-7-1, 4-5-4, and the like), but many of us have only a vague idea what they mean. You should know that they’re an important indicator of what those fertilizers contain, and how they can help you improve your soil and keep it healthy. The numbers represent the NPK content, where N, P, and K are the chemical symbols of three nutrients critical to plant growth: Nitrogen, Phosphorus, and Potassium, in that order. Each number tells you the percentage of the element present in the fertilizer by content.
Thus, if the NPK number is 10-2-4, that means the fertilizer offers 10% Nitrogen, 2% Phosphorus, and 4% Potassium by content. Nitrogen is integral to the development of leaves, blades, and other foliage. Phosphorus aids root development, while Potassium is a good overall nutrient that aids plant growth in general. A particular type of fertilizer may contain all three elements (in addition to dirt, fillers, amino acids and other micronutrients), or it may contain only one or two. If one of the trio is missing, it will be represented by a “0″ in the NPK number. For example, an NPK number of 0-7-1 means that the fertilizer contains no Nitrogen, 7% Phosphorus, and 1% Potassium.
Note that the NPK number applies whether the fertilizer is considered organic or chemical. For more information on NPK numbers, take a look at our detailed explanation here.
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