Perfect Sun LED
Well-Known Member
Hey, Neil here. What’s up my fellow growers? I have a modified Lukas Formula and will explain why it is better, and how you can know that whatever nutrients you are using is giving your cannabis the best possible feeding.
The first thing we need to know is what is the optimal feeding for marijuana. Many recent studies have been done growing marijuana to determine what ppm of each nutrient cannabis does best with. Interestingly, enough, this is very close to tomato plants.
Just in case you don’t know what NPK Ca Mg S is, let’s cover that.
N = nitrogen
P = Phosphorus
K = Potassium
Ca = Calcium
Mg = Magnesium
S = sulfur.
You might remember this from the periodic table. These are the major elements that plants need to survive and grow their best.
For example, cannabis did very well with low phosphorus (P) levels, from 11.5 ppm to 20 ppm. This lead to the most potent THC, CHD, etc levels. Don’t worry, I will show you an easy way to know how much ppms of each nutrient you are feeding your plants.
The test growing also showed that higher ppm of phosphorus (P) up to 30 ppm grew larger buds, but they said there might be a correlation in this causing lower THC, CBD, etc levels. You will be feeding your plants more than 30ppm of P anyway unless you have a 4 part system or something.
Regardless, test growing also showed that plants did great with phosphorus (P) levels of 55, and did not show toxicity up to 100 ppm and even 196 ppm. But as of now, they cannot determine if there was any benefit of going above 50 ppm.
Thus, optimal levels of P are between 20-50 ppm.
Test growing also showed that optimal levels of nitrogen (N) are between 100-155. It is best to reduce N to 100 during the last two weeks of flower. Here are other optimal levels.
Ideal levels for cannabis
N 150
P 30-50
K 160-250
Ca 100
Mg 50
S 40
Before we get into the modified Lukas formula and learn how to figure out the ppm you are feeding for each element, there are a few more things I wanted to cover.
Cannabis seems to grow very well when there is a 4
1 ratio of P, Ca, Mg, or at least close to it. Like a 3.51. This means if Mg is 50, then Ca should be around 100, and K around 150-200. Plants seem to grow bigger buds when potassium (K) levels are raised for one week during mid flower. So I would hit them with an extra PK booster then.
Okay, let’s look at the Lukas formula first, which is using General Hydroponics three-part Flora series, Flora Bloom and Flora Micro. It doesn’t use the grow, thus if you can buy these two separately, you can save money.
The Lukas Formula uses 8ml of Flora Micro and 16ml of Flora Bloom, so a 2:1 ratio. Use twice as much bloom as micro. You use these throughout the grow at different strengths.
Here are the ppm numbers we get when using this.
N 105 ppm
P 90 ppm
K 157 ppm
Ca 105 ppm
Mg 63 ppm
S 42ppm
Fe 2.1 ppm
How do we get these numbers? So there are two ways nutrient companies can list the percent of elements in their bottles. One is by percent of weight by volume and percent of weight by weight. Most use percent of weight by volume because this makes it easier for growers to solve for how much nutrients they need to reach a target ppm. This is why it is the standard. This means we do not need to calculate for the SG, specific gravity. If that makes no sense, that is fine. A lot of this might sound like jibberish. That is okay. It is nerdy shit that you don’t need to know.
We can see that these numbers are not bad compared to the ideal numbers. The P is a little high, but these levels did not show to be toxic or have ill effects. The nitrogen is a bit low, especially for late veg and early flower. You can make up for this using calmag plus, but that will also raise the calcium and magnesium, which are already a bit higher than optimal levels. But we do have a close to 3.51 ratio of K, Ca, Mg.
The modified version looks like this feeding 10ml of Flora Micro and 16ml of Flora Bloom.
N 132 ppm
P 90 ppm
K 161 ppm
Ca 132 ppm
Mg 63 ppm
S 42 ppm
Fe 2.64 ppm
This gives us a better feeding of nitrogen and potassium (K) still looks good. Calcium is a bit higher, but this will not harm the plants. I recommend using the Lukas formula for early veg and later flower, and the modified version during late veg and the first half of flower.
Okay, but before we keep going, how do you figure out what ppm you are feeding your plants? It is pretty simple. So you know the numbers on nutrients bottles NPK? Those numbers are the percentage of each of those elements in the bottle per percent of weight by volume. Meaning that, whatever volume we measure out, say 100ml, then the percent of nitrogen (N) in that 100ml of liquid is the same as if you poured out 200ml or 1000ml.
So if the bottle list the NPK as 5-4-8, then we have 5% nitrogen (N), 4% phosphorus (P), and 8% potassium (K). Some nutrients will also list the Mg and Ca on the back of the bottle. General Hydroponics does this. In fact, they tell us more than that.
Let’s get comfortable knowing how to calculate the ppm we will add to our 1 gallon of water if we feed with 8ml of Flora Micro and 16ml of Flora Bloom. We will do this for nitrogen first because P and K take an extra step, which we will learn after we feel comfortable with how to calculate ppm of nitrogen.
You can view the back labels on the general hydroponics site. Flora Bloom has no N. Flora Micro has 5% by volume. This means 100ml has 5% N and 500ml has 5% N. This makes the math a bit easier. It works like this. There is more than one way to do the math, but I find this method very easy.
Take the ml you are adding to a gallon of water, so in this case, we are adding 8ml of Flora Micro. We multiply that times the percent of nitrogen (N) in Flora Micro, so 5%.
First, here is the whole formula, then we will break it down.
8ml x 5% x 1000 / 3.78
The first part.
8ml x 5% = 0.4
Be sure to multiply by 5%, not just 5. So on your calculation, hit 8 then x then 5 then the % symbol then =.
You can also convert 5% to a decimal if your calculator doesn’t do percent. To do this do 5 divided by 100, which gives you 0.05. Then you multiply 8 x 0.05 = 0.4.
So we then multiply by 1000 because there is a correlation between grams and milliliters. We have a certain amount of grams of nitrogen in the liquid, and 1 ml of water weighs a gram. If we were adding 8ml to 1000ml of water, then we would just do
8ml x 5% x 1000 = 400 ppm
However, we are adding 8ml to 1 gallon of water, not 1000ml, so we need to figure out how many liters in a gallon, for 1000ml is a liter. It is 3.78, thus we divide 1000 by 3.78 to get the ppm for a gallon of water.
8 x 5% x 1000 / 3.78 = 105.8
So, break it down, 8 times 5% = 0.4. 0.4 x 1000 = 400. 400 divided by 3.78 = 105 ppm.
That is how you solve for the amount of nitrogen your nutrients are adding to a gallon of water. So for example, say your nutrients are a part A and part B. Part A has 3% nitrogen and Part B has 5% nitrogen. Because these kinds of ingredients measure equal parts of A and B, we can add the percentages together. 3 + 5 = 8%
Let’s say this nutrient calls for us feeding at 6ml per gallon.
6ml x 8% x 1000 / 3.78 = 126 ppm
On my phone calculator, I can run all that and get the right answer. Not all calculators do this, though, so you might have to do 6 x 8%, then hit =, Then do x 1000 and hit = then divided by 3.78 and hit =.
Now to solve for the Ca and Mg is the same as nitrogen. There is only calcium in Flora Micro at 5%. Thus
8ml x 5% x 1000 / 3.78 = 105 ppm
It is the same as the nitrogen. Magnesium (Mg) is only in Flora Bloom at 1.5%, and we are feeding with 16ml per gallon of Flora Bloom, so
16ml x 1.5% x 1000 / 3.78 = 63
Before we continue, we can save a step by dividing 1000 / 3.78 = 264.5
We can then just do
16ml x 1.5% x 264.5 = 63
You can even just do
16ml x 1.5% x 264 = 63.
Now to solve for P and K. This is where it gets a bit tricky. Most labels list PSO5 and K2O, as general hydroponics does. That is not the same as element P and K. To convert P2O5 to element P (phosphorus), we need to take the percent on the bottle of phosphate, and in this case, in Flora Bloom it is 5%, and multiply it by 0.43.
5 x 0.43 = 2.15
So the percent of element P (phosphorus) is 2.15% by volume.
We feed at Bloom at 16ml per gallon, so
16ml x 2.15% x 264 = 90 ppm
That gives us 90 ppm of P.
Now to figure out the potassium (K), we need to solve for the ppm in each bottle separately, then add the ppm together because we are feeding different amounts from each bottle, 8ml and 16ml.
First, we solve for K in Bloom. It lists K20 4%, so
4 x 0.83 = 3.32% of element K
Then for Micro. It list K20 as 1%, so
1 x 0.83 = 0.83
Then let’s solve for the ppm for each bottle, starting with bloom at 16ml
16ml x 3.32% x 264 = 140 ppm
Then micro at 8ml
8ml x 0.83 x 264 = 17.5
140 plus 17 = 157 ppm of element K in our gallon of water.
If you use all three parts and feed with different amounts of each part, then you have to do a lot more math, but it is the same process. Solve for N in each bottle, then add the final ppm from each bottle together.
If you use all three parts, you can get the levels of P much lower. The purpose of the Lukas formula and the modified version is to save money and make feeding easier and less time-consuming.
For the nutrients I use Perfect Nutrients, which you can learn more about in the link in my sig, I wanted the most optimal levels. It is a very simple system, yet though simple, it gives optimal levels of everything and uses the highest quality mineral you can from Haifa Group, sources in the USA.
I feed with equal parts of Complete A and Complete B. That is it. I do that for the whole grow and that gives me great levels of each element. I do 8ml and then 12ml of each. Here are the ppm this gives me.
8mL/G
N 105 ppm
P 36 ppm
K 113 ppm
Ca 77 ppm
Mg 36 ppm
S 28 ppm
Fe 1.47 ppm
This is perfect for the first half of veg, then I hit them with 12ml per gallon, which gives me.
12ml/G
N 158 ppm
P 54 ppm
K 170 ppm
Ca 116ppm
Mg 55 ppm
S 42 ppm
Fe 2 ppm
This gives me optimal levels of everything. However, during veg, I also hit them with a bit of my Fulvic Calmag, to raise the nitrogen Ca and Mg, which gives me even more ideal levels. I then drop the Fulvic Calmag during flower and switch to Flower Girl, to pump up the potassium to around 200, which is most optimal.
Finally, I drop back to 8ml during the last two weeks of flower to reduce the nitrogen back to 100 ppm, which has proven to be best for tight buds that are more frosty.
I don’t know of any other nutrient that is so simple with such optimal levels of everything tailored specifically for cannabis, based on recent research.
Thanks for reading. I hope you found this useful.
The first thing we need to know is what is the optimal feeding for marijuana. Many recent studies have been done growing marijuana to determine what ppm of each nutrient cannabis does best with. Interestingly, enough, this is very close to tomato plants.
Just in case you don’t know what NPK Ca Mg S is, let’s cover that.
N = nitrogen
P = Phosphorus
K = Potassium
Ca = Calcium
Mg = Magnesium
S = sulfur.
You might remember this from the periodic table. These are the major elements that plants need to survive and grow their best.
For example, cannabis did very well with low phosphorus (P) levels, from 11.5 ppm to 20 ppm. This lead to the most potent THC, CHD, etc levels. Don’t worry, I will show you an easy way to know how much ppms of each nutrient you are feeding your plants.
The test growing also showed that higher ppm of phosphorus (P) up to 30 ppm grew larger buds, but they said there might be a correlation in this causing lower THC, CBD, etc levels. You will be feeding your plants more than 30ppm of P anyway unless you have a 4 part system or something.
Regardless, test growing also showed that plants did great with phosphorus (P) levels of 55, and did not show toxicity up to 100 ppm and even 196 ppm. But as of now, they cannot determine if there was any benefit of going above 50 ppm.
Thus, optimal levels of P are between 20-50 ppm.
Test growing also showed that optimal levels of nitrogen (N) are between 100-155. It is best to reduce N to 100 during the last two weeks of flower. Here are other optimal levels.
Ideal levels for cannabis
N 150
P 30-50
K 160-250
Ca 100
Mg 50
S 40
Before we get into the modified Lukas formula and learn how to figure out the ppm you are feeding for each element, there are a few more things I wanted to cover.
Cannabis seems to grow very well when there is a 4
1 ratio of P, Ca, Mg, or at least close to it. Like a 3.51. This means if Mg is 50, then Ca should be around 100, and K around 150-200. Plants seem to grow bigger buds when potassium (K) levels are raised for one week during mid flower. So I would hit them with an extra PK booster then.Okay, let’s look at the Lukas formula first, which is using General Hydroponics three-part Flora series, Flora Bloom and Flora Micro. It doesn’t use the grow, thus if you can buy these two separately, you can save money.
The Lukas Formula uses 8ml of Flora Micro and 16ml of Flora Bloom, so a 2:1 ratio. Use twice as much bloom as micro. You use these throughout the grow at different strengths.
Here are the ppm numbers we get when using this.
N 105 ppm
P 90 ppm
K 157 ppm
Ca 105 ppm
Mg 63 ppm
S 42ppm
Fe 2.1 ppm
How do we get these numbers? So there are two ways nutrient companies can list the percent of elements in their bottles. One is by percent of weight by volume and percent of weight by weight. Most use percent of weight by volume because this makes it easier for growers to solve for how much nutrients they need to reach a target ppm. This is why it is the standard. This means we do not need to calculate for the SG, specific gravity. If that makes no sense, that is fine. A lot of this might sound like jibberish. That is okay. It is nerdy shit that you don’t need to know.
We can see that these numbers are not bad compared to the ideal numbers. The P is a little high, but these levels did not show to be toxic or have ill effects. The nitrogen is a bit low, especially for late veg and early flower. You can make up for this using calmag plus, but that will also raise the calcium and magnesium, which are already a bit higher than optimal levels. But we do have a close to 3.5
1 ratio of K, Ca, Mg.The modified version looks like this feeding 10ml of Flora Micro and 16ml of Flora Bloom.
N 132 ppm
P 90 ppm
K 161 ppm
Ca 132 ppm
Mg 63 ppm
S 42 ppm
Fe 2.64 ppm
This gives us a better feeding of nitrogen and potassium (K) still looks good. Calcium is a bit higher, but this will not harm the plants. I recommend using the Lukas formula for early veg and later flower, and the modified version during late veg and the first half of flower.
Okay, but before we keep going, how do you figure out what ppm you are feeding your plants? It is pretty simple. So you know the numbers on nutrients bottles NPK? Those numbers are the percentage of each of those elements in the bottle per percent of weight by volume. Meaning that, whatever volume we measure out, say 100ml, then the percent of nitrogen (N) in that 100ml of liquid is the same as if you poured out 200ml or 1000ml.
So if the bottle list the NPK as 5-4-8, then we have 5% nitrogen (N), 4% phosphorus (P), and 8% potassium (K). Some nutrients will also list the Mg and Ca on the back of the bottle. General Hydroponics does this. In fact, they tell us more than that.
Let’s get comfortable knowing how to calculate the ppm we will add to our 1 gallon of water if we feed with 8ml of Flora Micro and 16ml of Flora Bloom. We will do this for nitrogen first because P and K take an extra step, which we will learn after we feel comfortable with how to calculate ppm of nitrogen.
You can view the back labels on the general hydroponics site. Flora Bloom has no N. Flora Micro has 5% by volume. This means 100ml has 5% N and 500ml has 5% N. This makes the math a bit easier. It works like this. There is more than one way to do the math, but I find this method very easy.
Take the ml you are adding to a gallon of water, so in this case, we are adding 8ml of Flora Micro. We multiply that times the percent of nitrogen (N) in Flora Micro, so 5%.
First, here is the whole formula, then we will break it down.
8ml x 5% x 1000 / 3.78
The first part.
8ml x 5% = 0.4
Be sure to multiply by 5%, not just 5. So on your calculation, hit 8 then x then 5 then the % symbol then =.
You can also convert 5% to a decimal if your calculator doesn’t do percent. To do this do 5 divided by 100, which gives you 0.05. Then you multiply 8 x 0.05 = 0.4.
So we then multiply by 1000 because there is a correlation between grams and milliliters. We have a certain amount of grams of nitrogen in the liquid, and 1 ml of water weighs a gram. If we were adding 8ml to 1000ml of water, then we would just do
8ml x 5% x 1000 = 400 ppm
However, we are adding 8ml to 1 gallon of water, not 1000ml, so we need to figure out how many liters in a gallon, for 1000ml is a liter. It is 3.78, thus we divide 1000 by 3.78 to get the ppm for a gallon of water.
8 x 5% x 1000 / 3.78 = 105.8
So, break it down, 8 times 5% = 0.4. 0.4 x 1000 = 400. 400 divided by 3.78 = 105 ppm.
That is how you solve for the amount of nitrogen your nutrients are adding to a gallon of water. So for example, say your nutrients are a part A and part B. Part A has 3% nitrogen and Part B has 5% nitrogen. Because these kinds of ingredients measure equal parts of A and B, we can add the percentages together. 3 + 5 = 8%
Let’s say this nutrient calls for us feeding at 6ml per gallon.
6ml x 8% x 1000 / 3.78 = 126 ppm
On my phone calculator, I can run all that and get the right answer. Not all calculators do this, though, so you might have to do 6 x 8%, then hit =, Then do x 1000 and hit = then divided by 3.78 and hit =.
Now to solve for the Ca and Mg is the same as nitrogen. There is only calcium in Flora Micro at 5%. Thus
8ml x 5% x 1000 / 3.78 = 105 ppm
It is the same as the nitrogen. Magnesium (Mg) is only in Flora Bloom at 1.5%, and we are feeding with 16ml per gallon of Flora Bloom, so
16ml x 1.5% x 1000 / 3.78 = 63
Before we continue, we can save a step by dividing 1000 / 3.78 = 264.5
We can then just do
16ml x 1.5% x 264.5 = 63
You can even just do
16ml x 1.5% x 264 = 63.
Now to solve for P and K. This is where it gets a bit tricky. Most labels list PSO5 and K2O, as general hydroponics does. That is not the same as element P and K. To convert P2O5 to element P (phosphorus), we need to take the percent on the bottle of phosphate, and in this case, in Flora Bloom it is 5%, and multiply it by 0.43.
5 x 0.43 = 2.15
So the percent of element P (phosphorus) is 2.15% by volume.
We feed at Bloom at 16ml per gallon, so
16ml x 2.15% x 264 = 90 ppm
That gives us 90 ppm of P.
Now to figure out the potassium (K), we need to solve for the ppm in each bottle separately, then add the ppm together because we are feeding different amounts from each bottle, 8ml and 16ml.
First, we solve for K in Bloom. It lists K20 4%, so
4 x 0.83 = 3.32% of element K
Then for Micro. It list K20 as 1%, so
1 x 0.83 = 0.83
Then let’s solve for the ppm for each bottle, starting with bloom at 16ml
16ml x 3.32% x 264 = 140 ppm
Then micro at 8ml
8ml x 0.83 x 264 = 17.5
140 plus 17 = 157 ppm of element K in our gallon of water.
If you use all three parts and feed with different amounts of each part, then you have to do a lot more math, but it is the same process. Solve for N in each bottle, then add the final ppm from each bottle together.
If you use all three parts, you can get the levels of P much lower. The purpose of the Lukas formula and the modified version is to save money and make feeding easier and less time-consuming.
For the nutrients I use Perfect Nutrients, which you can learn more about in the link in my sig, I wanted the most optimal levels. It is a very simple system, yet though simple, it gives optimal levels of everything and uses the highest quality mineral you can from Haifa Group, sources in the USA.
I feed with equal parts of Complete A and Complete B. That is it. I do that for the whole grow and that gives me great levels of each element. I do 8ml and then 12ml of each. Here are the ppm this gives me.
8mL/G
N 105 ppm
P 36 ppm
K 113 ppm
Ca 77 ppm
Mg 36 ppm
S 28 ppm
Fe 1.47 ppm
This is perfect for the first half of veg, then I hit them with 12ml per gallon, which gives me.
12ml/G
N 158 ppm
P 54 ppm
K 170 ppm
Ca 116ppm
Mg 55 ppm
S 42 ppm
Fe 2 ppm
This gives me optimal levels of everything. However, during veg, I also hit them with a bit of my Fulvic Calmag, to raise the nitrogen Ca and Mg, which gives me even more ideal levels. I then drop the Fulvic Calmag during flower and switch to Flower Girl, to pump up the potassium to around 200, which is most optimal.
Finally, I drop back to 8ml during the last two weeks of flower to reduce the nitrogen back to 100 ppm, which has proven to be best for tight buds that are more frosty.
I don’t know of any other nutrient that is so simple with such optimal levels of everything tailored specifically for cannabis, based on recent research.
Thanks for reading. I hope you found this useful.
So I doubt if the followers of lucas are interested in learning how to calculate their elemental P and K from P205 & K20. 
