NPK: Plant macronutrients
This is the first in a series on plant nutrients and fertilizers.
When it comes to fertilizers you’ve probably noticed they’re labeled with 3 numbers such as 10-12-10. You may also see the letters N-P-K.
These are the periodic chart symbols for Nitrogen, Phosphorus and
Potassium.
The numbers are the percentage by weight of the three nutrients. So with the example above: 10% Nitrogen, 12% Phosphorous, 10% Potassium.
(Why don’t the numbers add up to 100?… there are fillers.)
By law, the product needs to be labeled with these nutrients and always in the same order: N-P-K.
Macro and micro-nutrients
There are 6 macro-nutrients.
Nitrogen, Phosphorus and Potassium are primary macro-nutrients.
Calcium (Ca), Sulfur (S), Magnesium (Mg) are secondary macro-nutrients.
Micro-nutrients include: Iron (Fe), Manganese (Mn), Boron (B), Copper (Cu), Molybdenum (Mo), Nickel (Ni), Chlorine (Cl), and Zinc (Zn).
Chemical (Inorganic) versus Organic fertilizers
Inorganic fertilizers are derived from, or with,
chemicals. They need to be water-soluble to be available to plants. A
consequence of this is once they’re dissolved in water, they’re vulnerable to evaporation, gasification and runoff.
To offset the losses, chemical fertilizers have a higher concentration of nutrients. Higher NPK values don’t necessarily equate to more plant nutrients.
The other issue with chemical fertilizers is the runoff which ends up in streams, lakes and ocean. High nitrogen runoff is credited for the large and growing algae dead zones in numerous bodies of water. Algae sucks up all the oxygen. Fish and sea life die.
With organic fertilizers, the “filler” is itself organic
material which also supplies micro and trace nutrients… everything is
used. Also, the nutrients are more slowly “released” to plants as they can use them.
Tho organic fertilizers have lower NPK values, the nutrients are more
completely used. So in the case - less is more.
Compost is about the best way you can feed your plants and keep the soil nutrient dense.
Other organic fertilizers include manures, worm castings, guanos, kelp, seaweed, blood meal and bone meal.
Organic fertilizers also are better soil aerators.
Nitrogen
Nitrogen helps plants produce more chlorophyll which in turn, promotes growth.
Few plants can convert atmospheric nitrogen so they need nitrogen in the soil.
Too much nitrogen and the plant will grow fast… but weak and disease vulnerable.
The form of nitrogen most frequently used in chemical fertilizers is
ammonium nitrate.
Phosphorous
Phosphorous supports root development and flowering.
It’s good to use with seedlings to get them established.
Chemical fertilizers generally use phosphoric acid/”triple super
phosphate”. This form can neutralize trace minerals in the soil.
Potassium
Potassium helps with disease resistance, extreme temperature tolerance and root development. It’s good to use during the winter (cold) and summer (hot).
Chemical fertilizers typically use Potassium Chloride or muriate of potash.
Potassium sulfate as a natural source of Potassium from the salt of The Great Salt Lake.
Plants aren’t all that different from humans in their need for nutrition. Where our best nutrition comes from broad array of fresh organic food, their best nutrition comes from nutrient dense organic soil.
Just as a plate of broccoli is a better, more available source of Vitamin C for us than a synthetically derived Vitamin C pill, so is organically fertile soil a better, more available source of N-P-K than chemical fertilizers.
Here are a few more like this one:
