I find my plants are always P def. most ratios I used have very little P. 3-1-5...5-2-6...3-1-2..the heavy 16 im using has the highest ratio and even then its 2.5:1 nitrogen to phos.
I was doing a little reading during lunch and the thing i was reading said to start with the MKP since its the only phosphorus source...it will also supply some K and to use potassium nitrate next to get the rest of the K and this also provides N. Then to use calcium nitrate which supplys rest of N with the addition if Ca. Then epsom salts for some Mg and S. Then the rest of the micros. They never mentioned anything about calcium nitrate being mixed separately.
The list was
calcium nitrate
magnesium sulfate heptahydrate
potassium nitrate
copper sulfate
potassium monobasic phosphate (mkp)
Manganese sulfate monohydrate
zinc sulfate dihydrate
sodium molybdate dihydrate
boric acid
iron EDTA (NaFeEDTA)
That's a big, long list that's far more complicated than it really needs to be for us end users. We don't need to mix them, just use them properly:
Most dry chemical manufacturers take the hard work out of mixing most of those salts by providing a base 'mix'. The one I use is called 'hi K' from Hydrogardens.com, and it has the whole list above already in it and in the right proportions, with only the following exceptions;
Calcium nitrate
Epsom salt (mag sulfate hep.)
MKP
Thus the mix already created for you has the right ratios of ammonia for pH stability, all the micronutrients and is guaranteed soluble at high concentrations to make stock solutions.
So why isn't EVERYTHING in there already? Also pretty straightforward; calcium nitrate needs to be mixed separately so it doesn't react with the rest of the nutes. The others are only needed at certain times in the growth cycle or for certain plants, so you can add them only as you need them.
My stock solution isn't particularly strong, but it is convenient; one gallon for a one hundred gallon changeout of my RDWC system.
In one bucket, I put in epsom salt, MKP if needed and some hot water to dissolve them. Once they've done so, I add the stock solution made from the mix I just explained. That's part one of two parts.
Part two is putting the calcium nitrate in a separate bucket and dissolving that in water. It dissolves very readily and doesn't need to stand for long, if at all. This is why I do it first and put it in the res before I mess with the other part. This way it gets plenty of time to mix and dilute so it can't react when I dump in the other bucket.
Pour the two buckets into your nutrient reservoir, which needs to be at least half full of fresh water- this is necessary so parts A and B don't get together at too high a solution strength and undergo any unwanted chemical reactions.
Why go to the trouble? Several reasons;
1. I know what's in my nutrient solution, no fudging. And I can control my own ratios.
2. I know what is NOT in my nutrient solution; there are lots of non fertilizer additives to speed up growth out there- including stuff that's not safe for people. Yes, it's already happened that nutrient manufacturers were forced to alter their formulas to remove carcinogenic materials! Remember, they don't have to tell you about anything they add except the N-P-K numbers.
3. I make my own stock solutions, adding to convenience. Stuff that's dry stays stable for a long time- years, just keep it dry. It's easy to measure on a scale and it's precise.
4. My hundred gallon changeout costs me less than one dollar.