NPK Fertilizer Numbers - what they really mean

Most online gardening information get this wrong. Find out what NPK fertilizer numbers really mean.

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NPK Fertilizer Numbers - what they really mean

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[jmctavishiii]

I personally appreciate learning what's true vs what's easy to understand. Knowledge is power, and knowledge builds upon itself. The more you more, the more you will know.

Thank you for providing factual info.

[skyland]

I love gardening and chemistry so this video was like an early birthday present for me! I saw this video first so now I'm off to watch the one you recommended at the end. Thank you so much!

[rubene]

Thanks for pointing out the obvious we all overlooked. Now it’s time for me to watch your other videos.

[thomaswiegmann]

Well well 5 10 10 etc they are best understood as proportions of compound rather than elemental weight

[brichter]

Very informative video. Thank you for the clarification of the numbers. Knowing the difference is so beneficial. Chemistry is important too. I recently found out that using dolomite garden lime can be detrimental to calcium absorption in tomato and pepper plants. A home gardener who has a Ph.D. in Genetics and Plant Breeding mentioned using calcium nitrate for his tomatoes and pepper plants. I asked him about BER, blossom end rot, and mentioned what amendments I use in my homemade potting mix, which dolomite lime was one of them to reduce the acidity of peat moss. His reply was that dolomitic lime contains magnesium. Mg is a metal similar to calcium but has a stronger charge than calcium. It can replace the calcium and cause BER. I am going to add calcium nitrate to my tomato and pepper plants to see if it will help with BER.

[Devilcity]

Have used 10-10-10 all my life in my vegetable garden, no issues so far. No soil test done either.

[cgirl]

This is why if you keep fish using your water change on your plants is so helpful. All the bad stuff in your tank is great stuff in your garden or potted plants.

[pamelashoemaker]

Whoa! I didnt even think about it like that! 🤩
But I do have a question:

This is greatly assuming that the proportions of the NPK containing molecules are all equal in the fertilizer, e.g. a 3lb bag of fertilizer contains 1lb of N containing molecules, 1lb P containing molecules and so on.
So here's my question:
Do fertilizer companies not balance the NPK molecules so that their product can reflect the NPK numbers they claim?

[yazidghanma]

Just came across your video and have to admit that I was surprised that all those prestigious companies and especially universities are getting it so wrong. An excellent explanation and the net figures are spot on. Happy that I watched the video. Thank you.

[forger]

WHY does the first number in the ratio refer to just pure Nitrogen rather than the compound it is supplied as, like with the other two numbers? Is there any reasoning behind this?

[Daniel_Callie]

Absolutely love your channel! Your presentation reminds me of my botany professor from years ago. Sharing and liking thank you,

[stellajohnson-vives]

Really good information. Really knowledgeable and clearly explained. Thank you

[calculatedrush]

This is a great video. I have been trying to understand plants more and this helped a ton. Extremely clear and simple.

I'm sure others have pointed it out but at 4:23 you said phosphorus but you meant potassium. I mix them up when I talk all the time.

[robertjohnson]

In southern Florida, the soil is naturally high in phosphate. So I need a fertilizer of the form X-0-X. It is difficult to find a fertilizer that is not for lawns(high nitrogen) with zero phosphate. I am growing vegetables. I had to go online to find something close to what I need. I found 10-0-6 which is the best fit for my soil. This fertilizer is still called for lawn applications. Seems low in Nitrogen for lawns.

[bobsbackyard]

Thank you. So what should I be using on my Bonsai and or potted plants?

[quantumxoc]

The country where I live has a regulation that fertilizer "grading", or labelling, must include the concentration of elemental NPK in an additional number in brackets after the ratio.
For example 3:1:5 (18), which would mean 18% of the product weight is pure NPK.
In the above example 1kg fertilizer would have 180g pure elemental NPK, which is divided into 9 parts (3+1+5). This means 1 part is 20g, which works out to 60g N (3 parts x 20g), 20g P (1 part x 20g) and 100g K (5 parts x 20g) per 1kg product.
Still takes some calculation, but at least the average person is able to work it out without needing to know the molar masses or atomic weights of compounds and elements.
This also help to gauge at a glance how "strong" the fertilizer is, a 3:1:5 (36) would be twice as concentrated as a 3:1:5 (18) and should be used in a halved dosage.

[kws]

Pavlis knows what he is talking about. Thank you Sir.

[jerrybessetteDIY]

When the Ag Extension Service says add X pounds of K per 1000 sq ft. is that the compound or adjusted number?

[MommaRock]

Thank you I'm trying to give myself a college level of understanding this process through all the input I can get on the internet it's good to get correct information 👍

[davidstick]

We write what we do for simplicity. And for over 100 years it has worked perfectly. Doing exactly what we ask of it. Why do we write it the way we do? Simple really. I will leave that response out so snowflakes don't get pissy. Here is all people need to know. We provide the ratio of utilizable nutrients per weight of the bag. Nothing more. Nothing nefarious.