Phosphorus fertilizers are designed to supply a key nutrient to growing plants, namely phosphorous. These fertilizers usually contain the element phosphorous, not in its pure form, but as one of several chemical compounds called phosphates. Choosing the best phosphorus fertilizer for your needs begins with identifying the needs of the plant or crop you are growing, testing the soil, and deciding on which application method is most appropriate.
Plants need many nutrients for healthy growth, but three elements are regarded as the most important and are popularly called the big three. Nitrogen, phosphorus, and potassium are these nutrients and the amount of each in a particular fertilizer is represented on the label by the symbols, N, P, and K respectively, followed by percentages of each nutrient present in the fertilizer, by weight. Fertilizers are available in a number of different formulas, each with different amounts of each nutrient.
In order to choose the best phosphorus fertilizer for your needs, research the plant or crop you intend to fertilize to learn as much as possible about its needs. Some plants require large amounts of phosphorus, but others may not need as much. Matching a fertilizer to a plant's needs is important to the plant's health and the overall success of cultivation. The Internet, your local library, or an agricultural extension are good sources of such information as are greenhouse professionals and garden clubs. Since many plants will benefit from a comprehensive fertilizer, it is a good idea to research how much nitrogen and potassium a plant requires requires as well.
Once you have determined the needs of a particular plant, test your soil for nutrient content or have it tested by your local agricultural extension office or other agency that provides this service. Soil testing kits are available through many home improvement stores, garden centers, mail order catalogs that carry gardening supplies, or the Internet. Many are inexpensive, and by following their instructions, you can learn a great deal about the nutrients present in your soil. If your soil is already rich in phosphorus, you may not need a fertilizer with high levels of phosphorus. Conversely, if your soil is phosphorus poor, you may need a fertilizer that supplies a great deal of it.
The final step in choosing the best phosphorus fertilizer is to determine what application method best suits your needs. Fertilizers for residential and light farming use are generally available in one of two forms — granules or liquid. Some fertilizers that are meant to be applied as a liquid may be concentrated or sold as crystals that must be dissolved in water. Granulated phosphorus fertilizers may be applied directly. Once you have decided which type you wish to use, you are ready to choose the best phosphorus fertilizer for your plants or crops.