all in one solution mathematics

[Toulouse]

Hello

I have been look at the all in one DIY TPN+ on JamesC website but I get a little confused with the mathematics. Not that it matter because I trust that I just follow the instructions and all will be OK but someone can explain me something on the maths?

If the mix is 500ml DI water with total 72.9g dry salts then I get to 572.9g (for using 1ml water = 1g)

If 48g is KNO3 and KNO3 breaks down to
N - 13.854%
o = 47.474%
K = 38.672%
Then that would mean that 48g is added to make 6.65g of N. divide by 572.9 that comes to 1.16% of solution yet James' calculations state 1.34%

Am i doing my math wrong? or I have missed something somewhere?

Thank in advance
Mane

 

[dw1305]

Hi all,
Yes it is the maths, it isn't add 72.9g of fertiliser to 500cm3 of water, but add water to the salts until the solution (with all the salts dissolved) has a volume of 500cm3. Because the density of the solution will be pretty close to 1 (1g = 1cm3), as you say, it will be about 427g (or cm3) of water.

cheers Darrel

 

[Toulouse]

thank you I understand now 🙂

 

[geoffbark]

Oh

I always read that you add the total amount of dry fert to the 500ml water when making solutioins, not add water to dry ferts upto 500g (ml)

oops

 

[ceg4048]

People, lets take a mini reality break. Who cares whether the solution is 1.16% vs 1.34%? If anyone thinks they'll see a difference they'll be fooling themselves. We are not in a laboratory trying to develop some kind of nuclear medicine to cure Turrets Syndrome here, we're just feeding our plants. Why on Earth would we worry about a 0.18% difference? This is like picking out the lint in your bellybutton just before you step on the scale in the doctors office because you're concerned that the extra weight of the lint might affect the readings. This is a complete non-issue. Mix it any way you want and just get on with it. Your plants won't care. These calculations are academic. The important thing is to feed you plants well and to not be afraid of adding nitrate/phosphate salts.

Cheers,