Three questions...

What is the NPK rating of your nutrients?

What is the type of light you use and how far away from the lettuce is it?

How often have you been changing your nurtients?

NPK is three part -

Fert is 8 - 15 - 36
Cal Nit is 15.5 - 0- 0
Mag Sulfate

I use Metal Halides that are 34 - 36" above canopy, they are air cooled

I change my nutrients every 2 weeks

What kind of system is it? EnF and drip systems may build up nutrient deposits on the medium.

This is a continuous NFT.

Well, I can't say for sure but it seems like your nutrient mix is very high in the P&K ratings. It is almost like you are using a "bloom" type mix instead of grow. With lettuce you really shouldn't need that much potassium and phosphorus. This could be the problem.

Like grizzman pointed out, sometimes nutrient salts can build up in your reservoir. This could be another cause of your tip burn. It sounds like your lighting setup should be very cool, what temperature does the grow area stay around?

I never get temps above 79 - 80 F when lights are on and it stays at 74 or lower when the lights are out. I chill the resevoir to 65 though, so the temps should be fine.

I am using Hydro-gardens commercial nutrients which are very tried and true in the industry. It seems that I always get a nice reaction after I change my tank but I really shouldn't have to change it more than every 2 weeks.

I was intitially told by Hydro-Gardens that the cause was due to me mixing all the dry components together (Fert., CaNitrate and epsom salt) because the Calcium Nitrate must be liquified separately. If not, it would cause binding of the other minerals. I did see a slimy residue in the tank prior to the change which now seems to be gone and staying gone. I add pre-liquified ingredients of the three now separately.

Plant analysis of these are consistently low in the micro's and high in the macros indicating lockout. I'm wondering if I should change my formula. It is currently 1 part fert, 1 part cal nit and 2/3 part mag sulfate (epsom salt). Maybe cut back on the fert or something. Still wondering what to do so I appreciate your questions.

Decided to change out resevoir again and found more slimy goo (technical for build up) in the lines and the tank. This has to be related to the deficiencies. Why would my nutrients be collecting as a residue vs. being used? I'm going to run a 24 hr water only and see if I can clean out the system and roots a little more. Roots overall look really good (thick and white). I cleaned out as many tubes as I could to make sure the slime was removed.

For some reason, my nutrients want to collect. Trying to figure out why so additional questions/opinions welcome.

Thanks all.

The slimy goo is probably algae. Although it could be a fungus, you said your roots look white and healthy. So I would figure probably algae. I don't know how your NFT system is constructed, but most have open ends that allow light in. That light is all that's needed (in a hydroponic system) to grow algae. The nutrients are the food source, you need water for the nutrient solution, so all that's left is light. Though I don't really think the algae would cause a tip burn, though I suppose it might be possible it contributes. Alage uses some of the nutrients, but it mostly just uses up the dissolved oxygen in the water (that might lead to a nutrient problem). As well as if it gets severe enough and covers the roots, it could suffocate the roots (I suppose that could keep the roots from absorbing the nutrients in that case too). Algae could also possibly feed other microorganisms that could be a problem.

Pictures of the leaves may help figure out if this is a nutrient deficiency and/or toxicity, or if it is of other causes.

Here are some pictures. Call me crazy but it seems to be slightly improving after a tank change. I've seen this before. Is it possible that the nutrients get out of balance in just one weeks time and need to be changed? I'm growing about 350 heads with a single 100 gallon tank.

The Romaine is the largest offender. The butterhead just seems to tighten up and form a small dense head. The other types appear to fair ok.

Here are some photos.

https://picasaweb.google.com/hydroscotty09/LettuceTipburnIssues72011?authuser=0amp;authkey=Gv1sRgCJbcy5r7r5KtywE&feat=directlink

Here is a link that might be useful: Lettuce Tipburn

Interesting indeed. Do you use water from the tap or do you run R/O through your system? From doing some research, tip burn would be caused by either chlorine toxicity, or boron accumulation leading to toxicity... other types of deficiencies and toxicities (according to this source) lead to chlorosis of the leaves before burning or dieng off.

Here is a link that might be useful: Symptoms of Deficiencies and Toxicities

I do use tap but prior to this I used Reverse Osmosis with the same results. My water was tested and was low in the following:

Nitrate Nit
Ammonia Nit
Phospor
Potassium
Zinc
Manganese
Iron
Copper
Carbonate

It had the following other items with values
Calcium at 43 ppm
mag - 24 ppm
sodium 16 ppm
chloride 18 ppm
sulfate 141 ppm
bicarbonate 95 ppm

pH of 7.2 and TDS of 250

Not sure if any of these could cause the issue but like I said earlier, it has happened with the RO water also.

All thought provoking ideas are needed. Thanks

One other question reagarding the pH is where Lettuce like the value to sit. I have been advised that the pH needs to stay around 5.8 - 6.0 but find it wants to wlak up the ladder to 6.2 - 6.4 where it stabilizes some. Could I be creating lockout forcing the pH down so low. Of course the pH climbs as the ec drops which is what I expect. After the tank change, the heads appear to eating better and the tipburn is improving. It's all got me puzzeled as I do not want to have to chnage the tank weekly.

hydro_scotty
Lettuce pH range 5.5 to 6.5, I would try for right in the middle of about 6.0. But I wouldn't worry about it if it fluctuates some, as long as it's within range. But I think your on the right track, 100 gallons for 350 plants comes out to just over 1/4 gallon per plant (0.285 gallons per plant). Small plants like lettuce should have a minimum of 1/2 gallon per plant of water volume (nutrient solution) as a general rule of thumb. Splitting your system into two systems, each fed by it's own 100 gallon reservoir should provide the minimum water volume for the 350 plants (0.571 gallons per plant). For the larger heads like Romaine you may want 3/4 gallons of water volume per plant.

One of the reasons the problem may seem to come and go is the size/age of the plants at the time. If the plants are larger, they will use up the nutrients faster, causing it to go out of balance faster. The smaller plants will still be affected, but the more larger plants in the system, the faster it goes out of balance overall.

Hello everyone - I think the tank size has been affecting me in a large way as homehydro pointed out. I am keeping the pH around 6.0 - 6.5 and changing the tank every 5 - 7 days to ensure the nutrient balance is maintained. All I can say is that the improvements have been quite dramatic to the point of the leaves growing around the tip burned area. I'll be splitting it or just buy a larger tank. Thanks for all the input. Fingers crossed I'm finally through this.

Ok. I have another update here. I let the EC climb back to 1 and started seeing the burn again. This is crazy because that is the total ec including my tap water which is basically 0.5. I lowered it back down to 0.87 or so and I see improvements but the EC has remained unchanged for 2 - 3 days while the pH climbs 0.2 or more per day. I'm just wondering if anyone knows why this is happening. If I raise the EC to 1, I get a fast drop to 0.9 which I assume is the macro nutrients being taken in. Just curious why there is such a big difference in performance based on a small 0.1 ec change???????
Any ideas?

Maybe there is bacteria in the system? Have you tried adding H2O2 or Florashield into your solution?

Its been awhile so the problem may not even exist anymore.