jesters missus
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What do those numbers on the fertilizer label mean?
Originally published by Dr. David E. Neil
CEO - Dyna-Gro Nutrition Solutions
Maximum Yield Australia - September / October 2008
N - Nitrogen
P - Phosphorus
K - Potassium
Most growers are aware that the three numbers on the fertilizer label refer to nitrogen (N), phosphorus (P) and Potassium (K), respectively, but many do not know exactly what the numbers signify.
In general, they refer to the weight of each of those elements expressed as a percent of the total weight of the net contents of the container.
The first number refers to the percentage, by weight, of elemental nitrogen regardless of the form in which it is present. That form may be Urea Nitrogen - Co(NH2)2, Ammoniacal Nitrogen - NH4 or Nitrate Nitrogen - NO3. The weight of the carbon, oxygen and hydrogen atoms in these various nitrogen containing molecules is not counted.
However, things are different when we get to phosphorus and potassium.
Phosphorus is expressed as the percentage, by weight, of phosphate - P2O3.
Potassium is expressed as the percentage, by weight of elemental potash or K2O.
From the atomic weights of phosphorus (31) and oxygen (16) we can calculate the percentage, by weight, of elemental phosphorus in the phosphate molecule at 43.7%
Similarly, from the atomic weights of potassium (39) and oxygen (16), we can calculate the percentage, by weight, of elemental potassium in the potash molecule at 83%.
What this means is that a fertilizer which is labeled 10-10-10
Originally published by Dr. David E. Neil
CEO - Dyna-Gro Nutrition Solutions
Maximum Yield Australia - September / October 2008
N - Nitrogen
P - Phosphorus
K - Potassium
Most growers are aware that the three numbers on the fertilizer label refer to nitrogen (N), phosphorus (P) and Potassium (K), respectively, but many do not know exactly what the numbers signify.
In general, they refer to the weight of each of those elements expressed as a percent of the total weight of the net contents of the container.
The first number refers to the percentage, by weight, of elemental nitrogen regardless of the form in which it is present. That form may be Urea Nitrogen - Co(NH2)2, Ammoniacal Nitrogen - NH4 or Nitrate Nitrogen - NO3. The weight of the carbon, oxygen and hydrogen atoms in these various nitrogen containing molecules is not counted.
However, things are different when we get to phosphorus and potassium.
Phosphorus is expressed as the percentage, by weight, of phosphate - P2O3.
Potassium is expressed as the percentage, by weight of elemental potash or K2O.
From the atomic weights of phosphorus (31) and oxygen (16) we can calculate the percentage, by weight, of elemental phosphorus in the phosphate molecule at 43.7%
Similarly, from the atomic weights of potassium (39) and oxygen (16), we can calculate the percentage, by weight, of elemental potassium in the potash molecule at 83%.
What this means is that a fertilizer which is labeled 10-10-10
is in reality, 10% elemental nitrogen, 4.37% elemental phosphorus (10 x 43-7%) and 8.3% elemental potassium (10 x 83%) by weight, or 10-4-8 in elemental terms.
Understanding these differences is important when you are attempting to utilize the numbers on the fertilizer label to calculate application rates to meet the nutritional requirements of your plants.
The other macronutrients - calcium (Ca), magnesium (mg), sulfur (S) and silicon (Si) are expressed as a percentage, by weight, of the elements themselves whether the element is part of a larger molecule, or not.
eg. The 2% calcium in Dyna-Gro's complete nutrition formulae is 2% element calcium by weight.
Trace elements such as iron (Fe), copper (cu), manganese (Mn), zinc (Zn), boron (B), molybdenum (Mo), chlorine (Cl), sodium (na), cobalt (Co) and nickle (Ni), some of which are present as a part of a larger chealate molecule to keep them in the solution and hence available to the plants.
The number refers to the percentage by weight of the trace element itself and not the accompanying EDTA chealate.
Understanding these differences is important when you are attempting to utilize the numbers on the fertilizer label to calculate application rates to meet the nutritional requirements of your plants.
The other macronutrients - calcium (Ca), magnesium (mg), sulfur (S) and silicon (Si) are expressed as a percentage, by weight, of the elements themselves whether the element is part of a larger molecule, or not.
eg. The 2% calcium in Dyna-Gro's complete nutrition formulae is 2% element calcium by weight.
Trace elements such as iron (Fe), copper (cu), manganese (Mn), zinc (Zn), boron (B), molybdenum (Mo), chlorine (Cl), sodium (na), cobalt (Co) and nickle (Ni), some of which are present as a part of a larger chealate molecule to keep them in the solution and hence available to the plants.
The number refers to the percentage by weight of the trace element itself and not the accompanying EDTA chealate.
