Hi all,
How would I know I'm getting *ppm of each? Is there a long winded equation or something?
Yes, there is in this case. To work out NO3 it's 5ppm K & 1.8ppm N or 8ppm NO3 (14 + 48 = 62/101= 61.4% NO3 so for each ppm of K you add 1.59 ppm NO3, so a dilution to give 5ppm K will also add 8ppm NO3.) (so approx 5ppm NO3 and 3ppm K.)
I like James calculator, very nifty and I'd definitely use it for the compounds he lists, but actually if you know the formula for any compound, and the RAM of the elements contained, you can use these simple equations to work out how many ppm of each element any weight of any compound will add:
----------------------------------(ppm nutrient x dilution rate)------------------------------------100
grams of compound =-----(
----------------------------------------------)--x----(
-----------------------------)
per litre of stock sol. -----------------------1000----------------------------------------% element in compound
and
---------------------(grams of compound x 1000)-------------% nutrient
ppm in tank = (
---------------------------------------) x
-------------------
-------------------------dilution rate-----------------------------100
So to add 3ppm K to a tank of 100 litres using KNO3, making a litre of stock solution and diluting the stock solution 1:5000: (add 0.2 ml for each litre of tank water - 20 ml to 100 litres)
------------(3 x 5000)-------100------15000-----100
38.9g = (
------------ ) x (
--------) =
-------- x
------- = 15 x 2.59 = 38.9g
--------------1000------------38.6------1000------38.6
or
-----------(38.9 x 1000)------38.9
3ppm = (
-----------------) x
------- = 7.78 x 0.39 = 3ppm.
----------------5000------------100
You can do the calculations on paper, but I use an EXCEL spreadsheet, as it makes things quicker.
cheers Darrel