Does the 'Lucas Formula' work with low wattage lights?

[w33d]

Hi folks! I'm new to this site so first of all I'd like to extend greetings out to the community. Your posts have been very informative, and I have tried to gather as much information as possible before asking any 'silly questions'. That being said, I would like to ask the community for some clarification on the 'Lucas Formula'.

As I understand it, the formula calls for GH micro / GH bloom in a 1:2 ratio at varying EC levels throughout the grow. Many of the articles I have read seemed to mention how large one's setup needs to be for best results, calling for lights of a given wattage with a reservoire of a given size.

I plan on trying something similar to this thread:
http://www.icmag.com/ic/showthread.php?t=141394

My setup will be RDWC rather than the (low pressure?) aeroponic setup used by Laylow0. I am unsure of my reservoire size, but it will probably be somewhere in the neighborhood of 10 to 20 gallons.

So to sum this all up, will I have any special concerns due to the use of a low wattage light? How often should I change the reservoire out to prevent salt buildup? Am I overthinking the whole thing?

Any comments or suggestions are appreciated. Thanks!

 

[Guest 18340]

I copied and pasted this from another site, someone asked Lucas a similar question to yours.
"to grow with the Lucas formula you use 8ml micro, 16ml bloom, GH Flora Series nutes. this should come in around 2.0 EC and works great for HPS light.. (or MH if you are oldschool and want lower yields)

for fluorescent light, I suggest you drop nutes strength to 5ml micro, 10ml bloom, per gallon of water, about EC 1.4".
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
All of the above came from Lucas himself.
Btw, Lucas formula does not call for varying ec levels, only the ratios mentioned above. When I use the 8/16 ration, I do so all the way from veg, thru flower.

 

[w33d]

Thanks for the advice. Does the wattage of the light effect the rate of evaporation from the reservoire? Any thoughts on how often to swap the solution out?

 

[Helis]

More lights = more nutrient uptake = greater transpiration in plants (generally)
Evaporation from a resevoir will generally go up with light wattage, but it's all about the temperature at and in the res itself IMO

I have recently been using the lucas formula in a 272w setup over 2.6 sq. ft (104w/sq. ft., 6846 lu/sq. ft.) and while growing from (mostly) bagseed, I have never needed to go over 1.0 EC with a 1:2 M:B ratio. Some are heavy sativas and needed even lighter feeding... The one indica-dom plant I do have (of better genetics, too) has liked every heavy feeding adjustment I've given but seemed to dislike much over 1.2 EC. I was originally following lucas's advice on using a 1.4 EC but believe this would work better from clone, and likely if my environment were a touch cooler/better vented. Either way approach everything lightly, consider 1.4 a possible goal but some strains may like ≤1.0 EC with this sort of light setup.
That said perhaps his ideal of "fluorescent lighting" is more saturated than mine. As usual ymmv.... Good luck!

 

[oldnooby]

I use it with only a 150hps and all is well.

 

[Guest 18340]

Also, theirs another Lucas "type" formula by Rez and head, it's 6ml/gal micro, 9ml/gal bloom.
Thats what I'm currently using for veg (I veg under t5's) and my plants thrive.

 

[w33d]

Thanks everyone for the great advice! Looks like very little can o wrong with this method. Is there a way to know when your solution needs to be swapped out? I've heard a range of answers including:

1. Each time you have topped the reservoir up with as much water as you started with initially.

2. Swap when flipping the plants over to flower.

3. Do not swap at all, in fact 3-4 complete grows are possible before a solution swap.

As I am new to hydro and would like to have *some* degree of success the first time I will lean to the side of caution if there is some type of risk. Once again thanks for your insight.

 

[Hydro-Soil]

Thanks everyone for the great advice! Looks like very little can o wrong with this method. Is there a way to know when your solution needs to be swapped out? I've heard a range of answers including:

1. Each time you have topped the reservoir up with as much water as you started with initially.

2. Swap when flipping the plants over to flower.

3. Do not swap at all, in fact 3-4 complete grows are possible before a solution swap.

As I am new to hydro and would like to have *some* degree of success the first time I will lean to the side of caution if there is some type of risk. Once again thanks for your insight.

I suggest reading a bit more on the Lucas Method as it covers both simple and advanced res management. The final choice will be up to you but the instructions are very simple to understand.

Stay Safe!

 

[w33d]

Thanks Hydro-Soil. I have read through much of the 'Ask Lucas' thread:
http://www.cannabis-world.org/cw/showthread.php?t=892

This seems to clarify my question in his second post where he says:

The original reservoir strategy I learned from pH was to dump and replace as you described, once an equal volume of addback water has reached. IOW, when a 20 gallon res, got 20 gallons of top up water, the res was dumped and refilled at fresh 0-8-16. This was not with pH adjusted water, because it works best to allow the res pH to fluctuate within a range of 5.3 to 6.3

An alternate reservoir management strategy I now prefer, is to add nutes to the reservoir in the addback water. The goal is to bring the reservoir back up to 1300ppm. In this strategy, I feel a single res change at harvest is sufficient.

Looks like it would be fine to attempt this with no reservoir swap until the end. If it works, giddy up! If not, Rome wasn't built in a day

 

[hilbie]

anybody compared rez/head flora series form at 6/9 to lucas to 8/16

anybody compared rez/head flora series form at 6/9 to lucas to 8/16

i was wondering if anybodys ran both and had any wisdom to share?

 

[LJB]

knna (for the uninitiated he's Spanish, so English wasn't his first lang.):

What determines optimun EC level is plant's transpiration level, not watering cycles. As far as the watering cycle is enough to keep water potential at a good level that dont difficulties transpiration, it dont depend on watering schedule at all, but of temps, humidity and CO2 level (or directly the three parameters together on the VPD (Vapor (water) Pressure Deficit)

The higher the transpiration rate, the EC should be lower (same amount of mg of nutes total, but dissolved on more water).

So independend of watering schedule, EC must be adjusting according to how much water a day plants are transpiring: how much gals of NS they consume on a daily (or weekly) basis. The higher, the lower EC.

Transpiration often is greatest in hot, dry (low relative humidity), windy weather.

 

[Guest 18340]

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