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What is NPK?

What is NPK?

The 3 numbers on fertilizer represents the value of the three macro nutrients used by plants. These macro nutrients are nitrogen (N), phosphorus (P) and potassium (K) or NPK for short.

The higher the number the more concentrated the nutrient is in the fertilizer. For example, numbers on fertilizer listed as 20-5-5 has four times more nitrogen in it than phosphorous and potassium. A 20-20-20 fertilizer has twice as much concentration of all three nutrients than 10-10-10.

The fertilizer numbers can be used to calculate how much of a fertilizer needs to be applied to equal 1 pound of the nutrient you are trying to add to the soil. So if the numbers on the fertilizer are 10-10-10, you can divide 100 by 10 and this will tell you that you need 10 pounds of the fertilizer to add 1 pound of the nutrient to the soil. If the fertilizer numbers were 20-20-20, you divide 100 by 20 and you know that it will take 5 pounds of the fertilizer to add 1 pound of the nutrient to the soil.

A fertilizer that contains only one macro nutrient will have 0 in the other values. For example, if a fertilizer is 10-0-0, than it only contains nitrogen.

These fertilizer numbers, also called NPK values, should appear on any fertilizer you purchase, whether it is an organic fertilizer or a chemical fertilizer.

Why Is NPK Important

So now that you know what the numbers on fertilizer mean, now you need to know why NPK is important to your plants. All plants need nitrogen, phosphorus and potassium to grow. Without enough of any one of these nutrients, a plant will fail.

(N) NITROGEN

Nitrogen is essential for plant growth. Nitrogen is a part of every living cell. The two forms of nitrogen which plants take up are in the ammonia (NH4) and nitrate (N03) ion forms. Most agronomic crops take up most of their nitrogen in the nitrate ion form. Plants will utilize N in the (NH4) ion form if present and available to the plant. Lack of nitrogen and chlorophyll means that plants cannot utilize sunlight as an energy source to carry on essential functions such as nutrient uptake. Research has proven foliar or leaf applications of nitrogen is one form of application that can supplement a plants nitrogen requirements during the growing cycle.

  • Nitrogen is necessary for chlorophyll synthesis and as a part of the chlorophyll molecule is involved in photosynthesis.
  • Nitrogen is also a component of amino acids.
  • Nitrogen is needed for growth of plants.

From the Greek words “nitron genes” meaning “nitre” and “forming” and the Latin word “nitrum”. Discovered in Scotland by Daniel Rutherford in 1772.

(P) PHOSPHORUS

Phosphate is a very important plant nutrient (macro-nutrient) needed for the plant to complete its normal production cycle. The highest level of P in young plants is found in tissue at the growing stage. As plants mature most of the P moves into the flower and then to the seed or fruit.

  • Phosphorus is needed for photosynthesis.
  • Phosphorus is necessary for plant respiration.
  • Phosphorus is essential for energy storage and transfer.
  • Phosphorus is needed for cell division.
  • Phosphorus is necessary for cell enlargement.
  • Phosphorus is essential for several other plant processes.

From the Greek word “phosphoros” meaning “bringer of light” (an ancient name for the planet Venus?). Discovered in Germany by Hennig Brand in 1669.

(K) POTASSIUM

An important function of Potassium is it’s influence in efficient water use. It helps in the process of opening and closing of plant leaf pores, called the stomata. Potassium is found in cell walls which surround stomata. Adequate amounts of Potassium can increase stress conditions on plants during drought conditions. Potassium is also responsible for producing quality crops.

  • Potassium is essential for protein synthesis.
  • Potassium is important in the breakdown of carbohydrates, providing energy for plants.
  • Potassium helps to control ionic balance.
  • Potassium is important in the translocation of minerals.
  • Potassium helps plants to overcome effects of disease.
  • Potassium is essential in the fruit formation stage.
  • Potassium helps improve shelf life of fruits and vegetables.
  • Potassium is involved in the activation of more than 60 enzymes which regulate the rates of major plant growth reactions.

From the English word “potash” and the Arabic word “qali” meaning alkali (“K” comes from the Latin word “kalium”). Discovered in England by Sir Humphrey Davy in 1807.