Topdressing dry meals: easy way to create your own dry fertilizer mix, and adjust NPK


Well-Known Member
Topdressing dry meals in a organic soil grow is the ultimate in kick-back feeding for plants. If you build your own soil mixes from scratch, you're gonna have a lot of leftover ammendments. Want to make a custom mix using a multitude of dry meals like : alfalfa, kelp, neem, fish bone, chicken manure pellets, guano, etc?
I'll show you how I make my own fertilizer mixes, and teach you how to manipulate those NPK values.
You might not care about NPK, but using the same ingredients you're already using in your grow but tweaked for nutrient ratio isn't going to hurt, is it? Cycling additions is always a good idea, and switching topdressing amendments through the season will do just that.

All you'll need is a variety of meals, some measuring cups, and a kitchen scale. I used some typical meals used in organic gardening.

- Quick explanation:
NPK values are based on % of mass. Most soil recipes are based on measurements of volume (cu.ft, gallons). I took my unit of measurement (1Cup), which is a measure of volume, and weighed 1Cup of each of my meals to get the mass (weight).

Approx. weights of 1Cup of meal/NPK values:
Alfalfa - (5oz) 2.5 - 0.5 - 2.5
Kelp - (7.5oz) 1 - 0.1 - 2
Crab - (7oz) 4 - 3 - 0
Neem - (6.5oz) 6 - 1 - 2
Fish Bone - (8oz) 3 - 16 - 0

Now multiply each value in a given NPK by the weight in ounces.
Ex. - Alfalfa weighs 5oz in a cup. N 2.5 x 5 = (12.5 ) P 0.5 x 5 = (2.5) K 2.5 x 5 = (12.5)
Do that for each meal.
Now add all the N values together. Then P and K.

The above values totaled:
111 - 158.75 - 40.5
Now add up the total amount of ounces:
5 + 7.5 + 7+ 6.5 + 8 = 34oz
Divide each NPK value by 34:

= 3.26 - 4.67 - 1.2
I'll use that for VEG.

For BLOOM I'll soften the nitrogen and even up the P and K numbers while adding sulfur and magnesium. I chose to use Langbeinite 0 - 0 - 22 aka sul-po-mag. I'll take 1 Cup of the above fert mix and add 1/3 Cup of Langbeinite.

So as before I'll weigh the 1/3 Cup of Langbeinite = 5.3oz

Follow all the steps before and multiply the NPK values by oz then add all the values together and we arrive at:
111 - 158.75 - 157.1 ÷ total oz (39.3)
2.8 - 4.03 - 3.99

You can see how different inputs will have an affect on the final NPK values. All you have to do is adjust the use of each ingredient. Hope this helps
- ColaC
Cover the top dressing with some straw and should be good. They need to break down to take advantage of the NPK stuff. Its not the same as a bottle with soluble fertilizer.

Bacteria and hypae are our friends here.
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