Farming and Animal Husbandry

Why do plants need fertilizers?
Answered by HowStuffWorks
  • HowStuffWorks

    HowStuffWorks

  1. Given the right soil and proper care, plants are usually all too happy to grow. But sometimes they need a little help getting out of the ground. Potassium, phosphorus and nitrogen are the most important chemical elements necessary for the growth of a plant. Often, though, it's difficult for plants to obtain these key chemical elements, or macronutrients, in nature. That's where fertilizer comes in handy. Fertilizer typically contains potassium, phosphorus and nitrogen because other elements, which are needed in lower quantities, are usually readily supplied in the soil.

    Broadly speaking, fertilizers fall under two main headings: organic and inorganic. The type of fertilizer we just discussed would be inorganic because chemicals nutrients are being added to the soil. Organic fertilizer, meanwhile, comes from nature, and includes many possible variations, such as fish meal, seaweed extract and wood ash [source: Garden Centers].

    And if you happen to be in the market for some fertilizer, you'll find some helpful measure of standardization in its labeling. When you're buying a new bag to give your plants the pop they need, you can find each of the primary elements listed on the bag's label. The label will have three numbers, each in bold. They will list the percentage amounts of nitrogen, phosphate (phosphorus) and potash (potassium). So, a hypothetical bag with a 15-15-15 label would contain 15 percent nitrogen, 15 percent phosphorus and 15 percent potassium. (The remaining percentage of the fertilizer is called ballast, which has no value to the plants.) You don't have to buy the same balance of all three nutrients. You can buy fertilizer that blends the nutrients together (fertilizer grades) or even just addresses one nutrient in particular. If you're after a  blend, it's recommended that you first obtain a soil sample taken from your work area so you'll know which fertilizer grade will have the best chance of success [source: North Carolina Dept. of Agriculture and Consumer Services].

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