For example, in Ewing's EMPRO fertilizer, the analysis is 28-3-10. The first number is always nitrogen (N), the second is phosphorus (P), and the third is potassium (K) which is why you see the NPK phrase. The numbers indicate a percentage by weight of each nutrient, so in this example, this bag consists of 28% Nitrogen.
Below the declaration of nutrient percentages, you will see the "derived from" statement. This is where the rubber meets the road so here are some important details including what each of these nutrients do.
Nitrogen (N) – Considered to be the most important nutrient, plants absorb more nitrogen than any other element. N is essential in multiple genetic, structural, and metabolic compounds including proteins, amino acids, enzymes, and others.
Nitrogen is also a key component of the production of chlorophyll which gives grasses their green color. Chlorophyll is crucial in the process that plants use to make food. Shoot growth (top growth) is stimulated by nitrogen as well. Nitrogen can also play a strong role in overall plant health. In many cases, nitrogen deficient plants will be more susceptible to diseases or increasingly likely to suffer from environmental stresses and traffic.
Nitrogen sources will vary but will be in the forms of Ammonium, Nitrate, or Urea. When listed as these forms, they are considered to be readily available to the plant, mineral sources, or loosely as "fast release" and may be called WSN (water soluble nitrogen).
Most fertilizers will have a slow-release component sometimes called EEF products (Enhanced Efficiency Fertilizers), and that will be expressed as a percentage of the total N. Slow-release sources may be coated, reacted, or natural organic, but the idea is that they feed over a period of time much longer than the mineral sources.
Typically turf fertilizers will be made up of a combination of both slow and fast N sources to give a quicker green up while providing nutrients for longer term feeding.
To make matters more confusing, there are also products that will contain stabilized N or nitrification or urease inhibitors as this product does. These are a discussion for another day, but the short story is that these products reduce volatilization or conversion of nitrogen to plant available forms and can feed for longer periods.
On this label, you will see two nitrogen forms: Ammonium phosphate and urea. Some of the nitrogen is stabilized with dicyandiamide, which is a nitrification inhibitor and N-(n-butyl) thiophosphoric triamide, a urease inhibitor. This is a mouthful, but all you should recognize is that these are stabilized sources. There are none of the other slow-release components in this product.
A lot of this can sound confusing, but we'll discuss more about these sources in a later post so there's a much greater understanding.
Please reach out to the Ewing Technical Services Team if there are any questions.