Fertiliser calculation.
 

I am trying switching to making up a solution instead of measuring out the dose dry every time.

My rains are fried with a bad cold, so can someone just check the math?

The container holds 300 mls and the logical liquid does is 3 mls, so the jar will need 120g, ie 100 x 1.2

So the way to make a solution of 300 mls is to put 300 mls into the jar, and mark the level.

Then emmpty the jar, put in the 120g and fill the jar to the 300ml mark, then each 3 ml does will contain 1.2g

Wih a cold like this I coud so easily see the decimal point being aywhere.

Bump, me and numbers are like me and being politically correct, it just doesn't happen. Need a little help here

I'm usually very math oriented, and saw this thread and thought "finally, my chance to contribute." But I can't follow bil's logic, so I'm not sure what calcs need to be done.

Glad I am not the only math fool.

I'm not disnumerate, but I need pencil and paper or two steps into a calculation I am lost.

The jar will hold 300mml of liquid.

the easy dose to remove each time would be 3 mls.

So, that would mean that 300 mls would give 100 doses.

One dose is 1.2g

Ten doses would be 12g so 100 should be 120g

Therefore put 120g in the jar and fill to the 300ml line with water.

I sit here with my brains throbbing to the extent that I can't trust my own logic.

So, does it pass muster?

bil, I believe your math is correct, but it is based on the one dose = 1.2 g figure. Where are you getting that? is it a good number?

Ah, ok. You've got liquid fertilizer, and one dose is 1.2g, so 100 doses would be 120g. You dissolve that into a 300ml container in such a way that you end up with 300ml of solution, then you can use 3ml of solution per dose.

I prefer this sort of calc (Thanks, Ray).

If you're looking for 25 ppm N with a fertilizer with the first number of 13, for example, that means you want 25mg N per kg (liter) of water in the final solution. As the powder is 13% N, that means you're shooting for 25/0.13=192 mg of fertilizer powder per liter. But that's kind of tough to measure, so we should make life easier and make a concentrate in which that much is contained in a smaller volume - for example, let's say we want that in 10 ml. 192 mg/10ml = 19200 mg/L, so of you put 20 grams in a liter, that's close enough, and 10 ml of that solution, diluted to 1 liter, gives you your ~ 25 ppm N solution for feeding.

Yeah, I am one of Ray's weak solution growers (well apart from the catasetinae which get the fertiliser so strong it is crystalising out (joke, not reall that strong))

I disolve 1.2g in 65 litres to give myself a 25ppm dose. rouble is, altho I have a nice little spoon to measure it out in, simply opening and closing the container means that enough moist air gets in to turn the fertiliser lumpy within a week. So, I thought I would have a go at making a concentrated solution, which would solve the problem. I have also made a cannister for it to go in to keep the daylight off and stop it from going green.

---------- Post added at 05:15 PM ---------- Previous post was at 05:12 PM ----------

I know I'm not well, but that just makes my head spin. Math is so not my thing.

I go over to Ray's site and the nice calculator tells me how much to put into a litre for a 25ppm solution. I multiply that by the volume of my spray, and off I go.

Bil, I hope you feel better soon.

The calculations you mention are correct. There is not enough information to address the issue of whether 1.2g is correct, but you seem certain of that.

Thanks for that. The 1.2g is based on Ray's calculator giving 0·21g per litre to obtain 25ppm. I then multiply that by 6.5 because that's what the sprayer holds.

OK, it's a little below 25 but everything is doing ok on it. I think it's 23ppm.

On my calculator 0.21g/l * 6.5l is closer to 1.4g, but I doubt it would make a difference to the plants. I don't think orchids can count up to 23, let alone 25.