The N to the P to the K



The N to the P to the K

Friday, July 11, 2014

The N to the P to the K

By Jennifer Ruisch


There are a lot of ways you can give your plants a leg up on the competition, and one of the easiest is with fertilizer. But which one to choose? One must know the ingredient ratios and the existing soil or water conditions. Which ingredients to add? Which to avoid? The answers might sound complicated, but really, they’re…elementary. (groan)

The Mighty Three

First the basics: The main things you need to know are your macro nutrients. These are the pillars that will support your plants’ good health and big yield. There are three macronutrients: nitrogen, phosphorus and potassium. These are the big players of the game, and their levels need to be balanced in order to get good results from your crop. The macro nutrients are expressed on bags of fertilizer with a printed ratio of three numbers, usually separated by dashes, for example, you might see 20-20-20, which would mean 20% of that particular type of fertilizer is made up of each nutrient, and the remainder would be some type of filler, usually mostly carbon. They are always presented in the order of NPK, so nitrogen is listed first, then phosphorus, then potassium. Each element performs a specific function in the growth and development of photosynthesizing life forms, and like any good boss, you have to know how to delegate the jobs.


Nitrogen’s job is to keep plants green. It helps foliage form. It keeps leaves green, which means your plant can increase surface area to process light into energy.  Big healthy leaves means more metabolic power for your plant. As your plants grow big and strong, they will need plenty of nitrogen to maintain those big old solar panels we call leaves.  You want to use plenty of nitrogen through the active growth stage all the way up to the flowering stage. Once your plant starts flowering, you can switch to a ratio of 3-20-20. This is a low nitrogen ratio that provides plenty of the other stuff for your buds to bust out. If you find yellow leaves on a plant, often a shot of nitrogen will help even things out. Some growers swear by urea. The stuff is loaded with nitrogen. You can buy it, or even make it yourself. I’ll give you three guesses how people make urea.

Decaying leaves, closeup shot

Phosphorus comes from decaying organic matter. It accelerates the growth of root tissue, which will allow your plants plenty of surface area to absorb other nutrients and water, and get them pumping up to the top by the flowers, where they matter most. Phosphorus is best applied with respect to timing, as it will assist in flowering BIG TIME.  If your leaves take on a purplish hue, you can add a bit of phosphorus to the mix to green things up.

Potassium, also known as potash, and known by its elemental symbol, “K”, helps plants to form chlorophyll, which will help them photosynthesize, and metabolize, and all the other desirable “izes”. Potassium also has the added benefit of helping your plant bolster its own immune system, strengthening its disease resistance. It’s like an immune supplement for your plants. Potassium can be found in wood ash, hence its other common name, potash. If you find that a cohort of crops is getting thrips and mealy bugs and molds and whatever else happens by, add some potassium to their regimen. It can mean the difference between a sickly plant, and one that is able to repair and defend itself against invaders.


Homework? And Tests???!!!

Once you’ve done your homework and gotten to know your macronutrients (you’re welcome), you need to decide which ratio best suites your setup. What you’ve gotta do is perform a soil or water test. Kits can be purchased at indoor garden centers, or even aquarium supply stores, for water tests. You want your medium to be Ph balanced, right at the sweet spot. Between 6.0 and 6.5. This slightly acidic substrate will provide the best environment for soaking up nutrients. Check your Ph, and while you’re down there, test for the presence of micro nutrients as well. These are calcium, magnesium, sulphur and carbon. All are required for your plants to grow and flower properly.

Liquid or Granules?

Once you figure out what you need, you can snag the right odds and ends from the garden center. You’ll have to decide if you want to use liquid nutrients or granules. Granules are easy to store, and just need to be suspended in water before adding to a reservoir. Liquid tends to be concentrated, so watch that heavy hand when you pour. More does not mean better, folks. It is definitely possible for your plants to O.D. on fertilizers. This is where the camps tend to split:

Organic or Synthetic?

You can try organic fertilizers, or synthetically produced ones. Organics are the remains of living organisms. For soil, you can buy blood or bone meal, for hydro setups, fish and squid emulsions are popular. Organic fertilizers are slowly broken down by bacteria in the soil, or in your water base. The plants cannot access nutrients until the bacteria have done their work. For this reason, it is nearly impossible to O.D. your plants on organics. You can add as much as you like, and the plants can absorb to their little hearts contents. Since your crop has to wait for the breakdown, one drawback of organics is that they can’t fix a problem overnight, so to speak. Plants in dire need of nutrients will have to wait for those bacteria to do their thing. The good news is, you can actually purchase and cultivate these beneficial bacteria. If you keep them well-fed, they can populate your setup and (like a good hydrofarmer) keep the whole process fluid.

Synthetics are a recent development, relatively speaking. Man-made fertilizers appeared in the mid twentieth century and have helped agriculture explode. Almost literally. Synthetics are faster acting and can mainline nutrients to a plant that is deficient of stressed. Dry synthetic granules tend to be cheaper than organics, and just need to be suspended in water before they are added to a system. One drawback of synthetics is that they are manufactured only with NPK, and insoluble fillers. Organic has NPK, plus carbon, and other nutrients. Synthetic will need to be supplemented.

Texture of plants group of green algae

I have one last tip to pull out of my hat. That, my friends, is seaweed. Seaweed provides many valuable services to flora cultivators of all types. It contains a little ingredient called mannitol, which helps plants absorb other nutrients. It also helps cultivate those beneficial bacteria we discussed before.

Organic or synthetic? Liquid or granule? Only you can decide which is best for your plants. When you do, let me know.


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