S
Snow Crash
- 150
- 18
Oh, and here's how you do it. P = (10,000p)/(V/m)
Where:
(big) P is the final element concentration in parts per million
(little) p is element concentration listed on the product label as a percentage
(big) V is total volume of the final solution in milliliters, or water + m
(little) m is the volume of nutrients used in milliliters
Percentages are actually "Parts Per Hundred"
All you need to do is convert your percentage to parts per million
To do that you multiply the percentage by 10,000
This will give you the ppm of that element in the bottle
To convert this to ppm of an element in solution you do some division.
First, divide the number of ml of nutrients you used by the number of ml of final solution.
Second, divide the nutrient ppm by the number you calculated first.
If you added 10ml of Nutrients to 3780ml of water (1 gallon) you would divide the calculated ppm by 379 (3780ml+10ml / 10ml) to get the final concentration in the solution.
Pretend you have a 1-5-3.5 nutrient and you are using 10ml of that to 1 gallon of water.
[without much regard for significant digits...]
N= (10,000 x 1) / (3790 / 10) = 10,000/379 = 26.38ppm
P= (10,000 x 5) / (3790 / 10) = 50,000/379 = 131.92ppm
K= (10,000 x 3.5) / (3790 / 10) = 35,000/379 = 92.35ppm
Then things get even trickier...
P listed on the bottle isn't just Phosphorus. It is a measurement by weight of P2O5 which is a little less than 45% actual Phosphorus. So... if you're a real stickler for measurement and detail you then need to reduce the ppm level of p. Multiply the readying by 0.44 to get the actual ppm of Phosphorus. Be mindful that most people and nutrient companies are talking about P2O5 when they suggest an NPK profile.
Potassium is in a similar boat. The listed K is actually K2O, and only 83% of what is listed is elemental potassium. So... again, multiply the final calculation by 0.83 to get the actual ppm level of that element.
Strangely enough, nitrogen is calculated for despite being listed in a variety of forms. The companies know their P205 is 44% of listed but it's "Big Ag" that controls how things are labeled. It really isn't a big deal because we're working with relational, inaccurate, information anyway.
Apply the formula to all the elements listed. Add them all together and multiply by 2. This is what the EC is supposed to be if the company you are getting your nutrients from are North American. Otherwise they are probably using a 0.7 conversion and you'd multiply that number by 1.3 to get the same EC that your nutrient company says you should get based on the labels.
Ultimately, your readings are going to be different which is why it is important to understand both where your readings "should" be and where they are measuring. This provides a clearer understanding of what your plants have access to than relying on just measuring, or just calculating. Doing both will make a dramatic improvement in any grow room when the information is recorded and applied.
For a slightly more mathematically inclined person the formula can also be represented as:
P = 10,000pm/V
This manipulation will allow you to use it in a spreadsheet and select 0 (zero) ml of nutrients used. Otherwise the formula would attempt to divide by zero and error. Stupid computers and their inability to divide by zero...
Where:
(big) P is the final element concentration in parts per million
(little) p is element concentration listed on the product label as a percentage
(big) V is total volume of the final solution in milliliters, or water + m
(little) m is the volume of nutrients used in milliliters
Percentages are actually "Parts Per Hundred"
All you need to do is convert your percentage to parts per million
To do that you multiply the percentage by 10,000
This will give you the ppm of that element in the bottle
To convert this to ppm of an element in solution you do some division.
First, divide the number of ml of nutrients you used by the number of ml of final solution.
Second, divide the nutrient ppm by the number you calculated first.
If you added 10ml of Nutrients to 3780ml of water (1 gallon) you would divide the calculated ppm by 379 (3780ml+10ml / 10ml) to get the final concentration in the solution.
Pretend you have a 1-5-3.5 nutrient and you are using 10ml of that to 1 gallon of water.
[without much regard for significant digits...]
N= (10,000 x 1) / (3790 / 10) = 10,000/379 = 26.38ppm
P= (10,000 x 5) / (3790 / 10) = 50,000/379 = 131.92ppm
K= (10,000 x 3.5) / (3790 / 10) = 35,000/379 = 92.35ppm
Then things get even trickier...
P listed on the bottle isn't just Phosphorus. It is a measurement by weight of P2O5 which is a little less than 45% actual Phosphorus. So... if you're a real stickler for measurement and detail you then need to reduce the ppm level of p. Multiply the readying by 0.44 to get the actual ppm of Phosphorus. Be mindful that most people and nutrient companies are talking about P2O5 when they suggest an NPK profile.
Potassium is in a similar boat. The listed K is actually K2O, and only 83% of what is listed is elemental potassium. So... again, multiply the final calculation by 0.83 to get the actual ppm level of that element.
Strangely enough, nitrogen is calculated for despite being listed in a variety of forms. The companies know their P205 is 44% of listed but it's "Big Ag" that controls how things are labeled. It really isn't a big deal because we're working with relational, inaccurate, information anyway.
Apply the formula to all the elements listed. Add them all together and multiply by 2. This is what the EC is supposed to be if the company you are getting your nutrients from are North American. Otherwise they are probably using a 0.7 conversion and you'd multiply that number by 1.3 to get the same EC that your nutrient company says you should get based on the labels.
Ultimately, your readings are going to be different which is why it is important to understand both where your readings "should" be and where they are measuring. This provides a clearer understanding of what your plants have access to than relying on just measuring, or just calculating. Doing both will make a dramatic improvement in any grow room when the information is recorded and applied.
For a slightly more mathematically inclined person the formula can also be represented as:
P = 10,000pm/V
This manipulation will allow you to use it in a spreadsheet and select 0 (zero) ml of nutrients used. Otherwise the formula would attempt to divide by zero and error. Stupid computers and their inability to divide by zero...
