Lucas Formula 2.0-How to maximize the Lucas Formula

ahh-ha!!! why would botanicare, or the guy at the hydro show tell me this... Id buy less. Thanks for the quick reply. and stellar info.

 

hehe...me too!

Ahh flushes. This could be the tie-breaker for me. I have a 50ish Gal tank that with the 3-part GH formula I change every week. Pain in the arse in job!

So you just do regular top-ups throughout? My thoughts on this is that my girls deserve fresh water every week and if that means emptying out however big a tank you've got, it's just part of growing.

It would be good if someone could figure out an add-back formula for the 3 part GH series. So far I just top up with same strength nutrients as what the tank is, having a little more control would be nice.

 

Nice thread bro. So many people are confused about the lucas method and adding back. I know i was until you enlightened me on my own thread. Thanks bro!
Sticky worthy in my eyes! GC needs to keep their ppm's in check! lol.

 

Here is what I do when its time to add back.

I take a sample and take readings just to see where my PH and PPM numbers are. I also see how many gallons I need to add back to reach full. I usually do this every 3 days and have to add back a gallon of ph adjusted water. I add that in with no nutes and give it a bit of time to mix.

I then take a sample and get the ppm reading. I use that ppm reading and my targer ppm reading and plug it into the formula below. The result give me the amount of micro to add back in in ml. I double that # for the amount of bloom.

Addback Formula - ((target - current) / target) * 8 ml per gallon * res gallons = Flora Micro (ml) double this figure to get Flora Bloom (ml)

I then take a gallon of solution out of my res, and add the nutes to that gallon to dilute. Then I add that back to the res. It gives me my target PPM every time. And as long as my ppm and ph #'s are right on, i see no reason to flush.

 

let me see if i'm following you.

if i set up my dwc and decide on 1000ppm as your target, and when i check it later and the water level has gone down 1 gallon but the ppm has dropped to 750ppm i need to raise my target ppm. conversely if the plant has consumed 1 gallon but tds has jumped to 1250ppm it needs less food and more water.

the question i have is, do you have a formula to determine what ppm would be more favorable to the plant?

 

What ever formula works for your strain. Whether it's 0-7-14 or 0-9-18, etc. as long as your ppms remain steady. it may take a day or two of watching your meter to figure what is good for your plants.
For me i start with 0-8-16 when i change my water.(every Sunday) From there if i mix
0-6-12 and add back with that, my ppms stay around 1000-1050. if i continue adding back full strength , my ppm's climb. Again, alot of it is your strain. Thanks to DR.T again for getting me dialed. With this method i've seen great growth rates and heathy looking plants. Also less stress from no ppm swings. Gotta keep your PH in check too though.

 

It actually does work just fine, even if dialed in. Because if you are dialed in, when you run the formula, you will come out to the exact amount of ml per gallon as you used in the beginning. What I mean is, if you are a gallon short of water, and you are dialed in, when you add the water and take a reading, the amount needed to reach your target ppm will be the amount per gallon that you used in the beginning. Example, I used the 0-8-16 formula in the beginning. When i was a gallon short, i added water back, took a reading, plugged the numbers into the formula, and came up with needing 8 ml of micro and 16 of grow to get back to my target ppm, the exact amount per gallon as I started with. So I was dialed in at the time, and the formula confirmed it. This last time I added water back, the ppm numbers were lower, the plants were eating more than drinking. So I adjusted my target ppm, added the water back, took a reading, came up with how much micro and bloom I needed to reach my new target ppm with the addback formula, added the nutes, and took a reading. The ppm was right where I wanted it to be, and taking readings for a few days afterwards, the ppm is holding steady. So the add back formula does actually work, whether dialed in, or making adjustments, at least for me its working just fine.

Of course you can not judge your reading before adding water, it has to be after. And I even used the formula with an adjusted ppm (I wanted to raise my ppm a bit due to yellow spots). The formula worked fine, and after adding nutes and taking a reading, my ppm was right where the formula said it would be.

So the add back formula actually does work weather dialed in, or needing an adjustment. And when using this, I have no need to flush.

 

Yep, I do as you do. I take my reading before adding water to see if I am dialed in or not. If I am, I know what the results of the add back formula will be, but I do it anyway just to confirm. But its when the numbers go astray, or i realize I need to adjust my nutes if I am not dialed in, I just adjust my target ppm in the add back formula to arrive at the new target ppm.

 

Thanks. This thread has been excellent, and I have definitely learned a thing or 2 from you. Here is what I am finding on my current grow of 1 White Widow and 1 Northern Lights. They are 5 weeks old and just entered the 12/12 period. For the first 3 1/2 weeks, the original 0-8-16 is exactly what they were looking for, and my ppm remained constant at around 1060 on my meter. So the original formula was dead on for them. After that though, explosive growth began, and my ppm began dropping. So now I have them at about 1300, and they are doing great and the #'s are staying steady. So thats what I like about the addback formula. It helps to figure out how much to add to get to a target ppm without having to do a full flush and starting over.

 

I can't believe I didn't put this in here. If you are doing add-back, and you know the capacity of your system, this is more accurate than Lucas' addback formula. It is not based on markup or markdown math, and is accurate to the ppm if you can measure your nutes that effectively. It can also account for starting ppm of tap water, and can utilize whichever conversion your meter uses.

Super's add-back calculator

http://docs.google.com/fileview?id=...mMtN2ZlNi00MGFhLTkyNWEtYmRlODkzNDU1OWZh&hl=en

 

Yo, That rocks. Thank you, MUCH appreciated.

 

That's what i'm here for lol. No problem hope it helps you out. The doc is right, always measure your EC/PPM/TDS BEFORE adding back any water. You need to know whether the ppms have risen or dropped since your last adjustment. a good rule that I follow is to move up or down in 100ppm increments. That 100ppm of difference can be the difference between perfectly formed leaves, and leaves with a little bit of tip burn from the nutes. go up another 100 ppm and that tip burn turns into worse burn.

My personal method for plants that I am unfamiliar with is to begin vegging (THIS ONLY APPLIES TO CLONES) the plants at around 850ppm@.7 conversion. then if the ppms drop the next time i check it, i go to 950. Most plants that I have dealt with will take the 850ppm no problem, but not all will take much more than that. I vegged my master kush in 950ppm@.7 the entire veg cycle, and the first week of 12/12. Only after the stretch started did the ppms start droppingand so i raised the ppmsand they have balanced at 1100 for the time being. Always start low, then work your way up. You will see alot of people on GC and other sites that have DWC or other hydro, but they have been vegging their plants for 2 or 3 or 4 weeks even and they are still small, and then they wonder why the plants are growing so slowly. If you overfeed a small plant, it WILL stunt its growth (even if you don't see the burn, alot of times it looks like super dark green leaves that are kind of wavy on the surface instead of smooth like they should be). Unless you are doing some serious training or scrogging etc, you should never need to veg any longer than a month in a good dwc. If it is not big enough to flower after a month either something is wrong, or you must want to grow 10' trees.

Sorry for the long post, super blazed.

 

I'm doing my first grow with the DWC & the Lucus Formula, and I like it. Having only done GH & Ebb/Flow before, I've had some interesting experiences.

I have 2 14 gal rubbermaid tubs, one for 1 plant and one for a res. My fill line is at 8 gallons, so while my plant and root mass was smaller, I was calculating for 16 gallons. It worked fine for the 1st month of flower, but then I started seeing higher ppms and lower pH. As you more experience growers have already figured out, my root mass had increased so much that it was displacing several gallons, and throwing my addback calculation way off.

So anyone reading this, who is new to DWC/LF, learn from my mistake and dump & refill every few weeks so you can get an idea of the true number of gallons in your system.

Live and learn!

 

Not necessary. Running the LF with no flushes and my numbers are spot on. I love no flushes, and never plan on doing any. Easy enough to make adjustments based on a little bit of displacement. And my ppm and ph is remaining spot on. I love the LF and I love the spreadsheet superusa posted for how much to addback. Sorry your numbers went astray, but still, no flushes necessary with the LF. Good Luck with the rest of your grow.

PS If your ppm #'s were going up, you do realize you could adjust your nute level to bring it down right? You could also just add PH adjusted water to bring the numbers down. Once your target ppm # changes, adjust your target ppm for those changes. I started my grow at about 1060 ppm. They loved it for a while. Now they like 1200. Last addback, I saw they drank more than they ate, so I made the adjustment, and bam, perfect #'s again. No flushes. Flushes are a real PITA.