The Fertilizer Numbers Printed On The Bag - What Do They Mean?There are three fertilizer numbers printed prominently on every bag, box or bottle of garden fertilizer that you buy. Do you know what they mean? If you know the code, you’ll know which to buy for the plants you want to grow, and how much to use for best results. It’s simple really. The three numbers represent the three primary nutrients that every plant needs in large quantity to grow. They are Nitrogen (N), Phosphorus (P) and Potassium (K), and they will always be listed in that order (N-P-K). The numbers indicate the amount of each of the plant nutrients as a percentage of the total content. If the fertilizer bag reads 20-8-8 and weighs 25 pounds, it contains 5 pounds of nitrogen (N), 2 pounds of phosphorus, and 2 pounds of potassium. Since that only totals 9 pounds, the remaining 16 pounds in the bag will consist of other secondary or trace elements that plants need, or inert material that doesn’t really feed your plants. Pretty good math for a garden gnome , huh! Because fertilizer can be expensive, farmers depend on soil tests before they plant a crop. The results come with recommendations on how much of each major nutrient to add at planting time given in pounds per acre. If you get a soil test for your garden, similar recommendations will be given, though they will be in pounds per 1000 square feet. Why are the fertilizer numbers important to you? If you are planting a very large garden, the cost of fertilizer would justify testing so that you only have to apply as much fertilizer as is absolutely necessary. But even in a smaller garden, the numbers are still important to help you know what type of fertilizer to use. Corn, for example, is in the grass family and is a high nitrogen feeder. The best choice is one that is higher in nitrogen, like a lawn fertilizer. The numbers might read 20-10-10. Leafy greens also need lots of nitrogen so they might like a similar diet. Tomatoes, cucumbers and peppers (fruiting vegetables) and flowers need more phosphorus than nitrogen, so a better choice might be 10-20-10 or 5-15-5. You get the idea. Chemical fertilizers are potent, and will have higher numbers, so less is needed at a time. But they are water-soluble and leach away more quickly. They need to be applied more frequently, usually two or three times during the growing season. Organic fertilizers are natural and less potent, containing more inert matter. You will need to apply more total pounds at a time, but they break down slower so they won’t have to be applied as often. Usually, once at planting time is sufficient. Lack of any of the major plant nutrients will spell disaster for your garden, so watch the fertilizer numbers. Happy gardening, Geefrank
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