NPK fertilizer refers to the three elemental nutrients found in common garden fertilizer: nitrogen (N), phosphorus (P) and potassium (K), or potash. Also seen as N-P-K, the hyphens are representative of the percentages of each element within the fertilizer. These three major elements are important nutrients for overall plant health, and depending on the type of plant species, will have a varying effect on how well a garden will thrive.
At any home improvement center, there are a variety of choices when it comes to NPK fertilizers. The numbers seen on the bags represent, in order, the percentages of nitrogen, phosphorus, and potassium contained within the mixture. A bag of 10-20-10 fertilizer will contain 10% nitrogen, 20% phosphorous, and 10% potassium.
Nitrogen functions as a means for the plant to produce more chlorophyll. This will result in abundant growth and allow for a dark green color. Many NPK lawn fertilizers have a high content of nitrogen in order to help produce lush, green grass.
Phosphorus aids in the initial growth of plants by contributing to root development and healthy flowering. Higher concentrations of phosphorus can be helpful when planting a new garden or sowing a lawn.
Potassium in NPK fertilizer provides an immune boost to plants by protecting them from certain diseases. It also aids in solid root development. Potassium also offers protection against seasonal weather such as extreme cold or drought.
In addition to plant type, some other considerations for choosing the right type of NPK fertilizer should include water solubility and the type of soil being used. Whether the fertilizer is organic or chemically produced is also an important consideration. Natural fertilizer will typically contain lower levels of nutrients than chemically produced fertilizer.
Another choice for the gardener is whether to use solid or liquid mixtures of fertilizer. In general, a liquid fertilizer will need to be applied to the area more frequently, and is prone to being washed away by rain, while solid fertilizer stands a better chance of absorption. While choosing which type of NPK fertilizer to use may seem confusing, a typical rule of thumb is that flowering plants and vegetables will require more fertilizer with a higher level of nitrogen, while slow-growing plants will need less fertilizer.