» Simple Answers to Complicated Fertilizer Questions

Simple Answers to Complicated Fertilizer Questions

Q. Several years ago I was able to buy fertilizer components from an agricultural fertilizer plant. The man who ran the plant was very knowledgable and understood what I was trying to achieve with the Mittleider Grow Boxes. He sold me all the components and I still have some of them. One of the things I have is 50 lbs. of potassium chloride. I neglected to write on it the NPK numbers. My source died and the plant seems to have closed down since we lived in NM the last time.

So my first question is what is the ice melt (potassium cloride) NPK number?

Mr. Kennard told me that if I could get these items I’d have a great compound:
34-0-0 use 10#
0-45-0 use 4#
0-0-60 use 6#
add 3# epsom salt

should I use 6# of the potassium cloride to finish this if I ever find a supplier again?

so here is what I was able to get
ammonium sulfate 21-0-0
triple super phosphate 18-46-0
potassium cloride
magnisium sulfate

The man from the local fertilizer plant said to use:
sulphur pellets instead of gypsum (in the Pre-Plant mix)
ammonium sulfate use 10#
magnesium sulfate use 6#
triple super phosphate use 1.25#
potassimum chloride use 6#
boron use 10 grams

What do you think of his recipe?

Someone from the Scotts company told me something that doesn’t make sense. I don’t think they understand what y’all are trying to do here. This is part of her note.

“Ms. Friend, a 45-45-45 mix would become a 15-15-15 due to percentage of weight (45-45-45 is divided by 3) The analysis could be too much fertilizer for your vegetables in the boxes. Are the nutrients you want to combine a slow-release or agricultural grade? You may want to contact the manufacturer of the products you have to make sure they are safe for vegetable plantings.”

Thanks for your help. I’m confident you can help me understand how to get this stuff mixed up. We had over 1000 tomatoes from 5 plants the last time we did this with plenty of sunshine. We look forward to landscaping our new yard with vegetable beds, fruit trees, and berry bushes.


A. First, your potassium chloride is 0-0-60, so it is good for what you are trying to do. And yes, if you were using the other ingredients 6# of this would be right.

The fellow from the local fertilizer plant does not know fertilizing plants as well as Dr. Jacob Mittleider, but that’s to be expected, because NO-ONE does. He is out on several points, but he got two out of five right. By the way diammonium phosphate is the name of 18-46-0. It’s known all around the world as DAP.

What you are after is a mix with a ratio of 110-60-110. So, using the materials you say you can get here’s what you should use:

(I invite you serious gardeners to do the calculations to prove this. You will forever after be able to mix the correct fertilizer mix, no matter what your source material is)

21-0-0 13.5#

18-46-0 4.5#

0-0-60 6.0#

Mag Sulfate 3.3#

To this you should add one 8 ½ ounce package of the Mittleider Micro-Mix.

Do not use sulfur pellets INSTEAD of gypsum. Gypsum is the source for essential calcium in high pH soils. If you have extremely high pH you might need some sulfur, but never instead of your calcium. Also, gypsum has sulfur in it, so you usually don’t need added sulfur.

The Scotts woman was trying to tell you that if you combine (as a hypothetical example) 100# of Urea, which is actually 46-0-0, 100# of triple super phosphate, which is 0-45-0, and 100# of potassium sulfate, which in some places might be as low as 0-0-45, you would have the following:

Fertilizer Analysis Weight purchased # of N # of P # of K # of Inert Matls

45-0-0 100# 45 0 0 55

0-45-0 100# 0 45 0 55

0-0-45 100# 0 0 45 55

300# 45 45 45 165

You would still only have 45# of each of the three mineral nutrients, but you would have 300# of total fertilizer. 45 as a percentage of 300 is only 15% – the rest being inert materials. You see then that you end up with a mix of 15-15-15.

The 15-15-15 is most assuredly safe for use on your vegetable garden. And it is typically agricultural grade, rather than slow release. We therefore use a very small amount and apply it each week – until 3 weeks before the havest for single crop plants, and until 8 weeks before the END of the harvest for ever-bearing crops.