The N-P-K ratio is the percentage by volume of nitrogen (chemical symbol N), phosphorus (P), and potassium (K) in fertilizer. A 16-16-16 fertilizer, for example, contains 16% nitrogen, 16% phosphorus, and 16% potassium.
How is NPK Calculated?
To calculate the pounds of nitrogen in a bag of fertilizer, multiply the weight of the bag by the percent nitrogen (this is the first number in the N-P-K designation on the front of the bag). Then divide the pounds of nitrogen by the area the bag states it will cover to get the pounds of nitrogen per 1,000 sq. ft.
Roles of NPK
The first number of the ratio indicates the amount of nitrogen in the fertilizer. Nitrogen serves a few different roles but its primary benefit to grass is to help produce lush, green leaves. The second element is phosphorus, which is focused on more of the downward growth and fuels important developments such as root growth. The final nutrient represented in the ratio is potassium. This particular nutrient focuses more on resistance. If you already have an established lawn that’s starting to suffer from stress or diseases then the application of potassium is crucial to the health of the grass.
What’s the Best Ratio?
The NPK ratio represents is the percentage of nitrogen (N), phosphorus (P), and potassium (K) in the fertilizer. So how do you what’s best for what ratio? Here are some basic rules to follow. If you are starting a new lawn then get lawn fertilizer that has a higher percentage of phosphorus and potassium. At this stage, it’s important to focus on root development and disease resistance.
If you are installing a new layer of sod then apply a similar ratio to what you would use for new lawns. Although new sod does have established grass, the roots themselves have been shaved off so it is vital to up the amount of phosphorus in the soil for root development purposes.
Finally, if you are well into the gardening season and have an established lawn then focus on using a fertilizer that has a higher composition of nitrogen. Before Using Lawn Fertilizer perform a test to determine the amount of nutrients that already exist in the soil. This can be done on your own through the use of NPK soil test kit.
Partial Source: http://www.jgilorganic.com/npk-lawn-care/
