Calcium Magnesium questions

[consettbay2003]

Gonewild,
It actually 2% magnesium oxide. I mistakenly assumed it was magnesium sulphate.

Macronutrients:
Nitrogen 26%
Nitrate nitrogen (NO3-N) 15.5%
Ammoniacal nitrogen 10.5%

Phosphorus Pentoxide Soluble (P2O5) 6%

Potassium Oxide Soluble (K2O) 11%


Micronutrients:
Magnesium oxide 2%
Boron (B) 300mg/kg
Copper (Cu) 200mg/kg
Chelated Iron 1533mg/kg
Manganese (Mn) 1000mg/kg
Molybdenum (Mo) 120mg/kg
Zinc (Zn) 270mg/kg

It seems I am low in magnesium, and lacking sulphur and calcium.

 

[gonewild]

Consettbay,
Here is a recipe to make a ratio similar to the MSU formula I use. The percentages are all rounded off and are approximate values.

Start with the 15-7-30 fertilizer formula as the base. I am assuming it has 2%magnesium content, if not we need to slightly readjust this recipe.

Mix these amounts together in the dry salt form. (Mix very well, make sure all lumps are crushed). Measure accurately.

10 parts 15-7-30 fertilizer.
7 parts Calcium nitrate.
3 parts Magnesium sulfate (Epsom salt).

Once mixed this gives you a fertilizer of (13-3.5-15-6.7-2.4)
13% Nitrogen
3.5% Phosphorous
15% Potassium
6.7% Calcium
2.4% Magnesium

If you mix 1/2 tsp/gallon of this new formula you will have about the same nitrogen level you are applying now (86 ppm), but you will have more potassium, calcium and magnesium which will raise your total ppm about 80 ppm, not a problem.

To get the calcium % higher we would need to raise the nitrogen level higher than the potassium which would not be similar to the MSU formula. To raise the calcium and keep the NPK ratio I think we would need to use some Potassium nitrate also. But I think the 6.7% calcium is enough and it is a 3:1 ratio with magnesium which is a little higher than the MSU.

You should also add a micro nutrient mix to give all the nutrients the MSU formula has and plants need.

Your current fertilizer has a lot higher nitrogen ratio with NPK 26-6-11.
If you want to keep using the high nitrogen balance which is not similar to the MSU formula you can mix equal parts of the NPK26-6-11 with Calcium nitrate and wind up with NPK21-3-5.5 with 9.5% calcium added.

Depending on what media you grow in with the high nitrogen ratio you are probably either wasting nitrogen or underfeeding potassium.

Hope this makes sense and helps.
If anybody cares to dispute my calculations I'm happy to listen.

 

[consettbay2003]

Thanks Gonewild, I really appreciate the time and effort you have put into helping me to get a more balanced fertilizer. I hope others have benefited from your generosity on this thread.

Bill

 

[gonewild]

Gonewild,
It actually 2% magnesium oxide. I mistakenly assumed it was magnesium sulphate.

Then it only has about half as much actual magnesium. That's not a problem because there is some extra in Calcium nitrate that I did not calculate in to what I suggested.

Micronutrients:
Magnesium oxide 2%
Boron (B) 300mg/kg
Copper (Cu) 200mg/kg
Chelated Iron 1533mg/kg
Manganese (Mn) 1000mg/kg
Molybdenum (Mo) 120mg/kg
Zinc (Zn) 270mg/kg

With these already in the base fertilizer you won't need to add micro nutrients as I suggested.

It seems I am low in magnesium, and lacking sulphur and calcium.

You will get about 2% sulfur in the new recipe with the addition of the Magnesium sulfate.

 

[gonewild]

Thanks Gonewild, I really appreciate the time and effort you have put into helping me to get a more balanced fertilizer. I hope others have benefited from your generosity on this thread.

Bill

Your welcome. Thanks for asking the question.
Where there is a will there is a way. :wink: