Lettuce tip burn issue in indoor hydroponic

Asked June 14, 2016, 4:03 AM EDT

I am doing indoor hydroponic to grow some vegetables as a hobby but I always bumped into issue where all kind of vegetables that I grow has a common issue -- TIP BURN.

Here is my setup
Kratky method (non-circulating hydroponic) - 1 liter and 4 liters containers
Using two tubes of T5 6400K fluorescent light (21 watt) in 4X1 feet area (small area in my office desk) running 16 hours a day with timer.

Environment
Humidity is 55-60%
Temperature is 24-26 degree Celsius

Water and Nutrients
PH is about 6.2
Using A & B powdered nutrient that need to mix with water in separate container to be concentrated solution, then take each part of it to make up a complete hydroponic nutrient solution. I bought it from this site
http://www.scomart.com/Hydroponic-Nutrient-Powder-Leaf-Grow-Fertilizer-10-Liter-FTM-10L-FA-LG-FTM-10...

Basically it is a 30-10-40 hydroponic nutrient which is quite different from people's recommend in terms of N-P-K ratio.
The nutrient that I have used, I have tried with EC = 1.0 and EC = 0.7 for growing lettuce (buttercrunch, red leaf lettuce, lollo bionda), but all having tip burn issue. The tip burn issue only happen on the older leaves, young leaves are looking fine.

After reading through many articles on the web, there is a question in my mind, some websites have summarized a table of what EC/cF/PPM to use for each type of vegetable, but there are plenty of hydroponic nutrient in the market with different N-P-K ratio, how does this N-P-K ratio impact the concentration of the nutrient in EC/cF/PPM? Recommended EC for lettuce is 0.8-1.2, is this EC value still valid since I am using pretty high N-P-K hydroponic nutrient? Comparing the nutrient that I am using and hydroponic nutrient with N-P-K of 3-1-2 as example, how different it is in terms of EC value?

Here is some photos of my plants, cherry belle radish, lollo bionda lettuce and red leaf lettuce. Please help!

Outside United States

3 Responses

The following reference might be helpful in explaining some of the physiology behind tipburn in lettuce: http://www.e-gro.org/pdf/2015_431.pdf

Ideally, you would not want the ec of the nutrient solution to rise above 1.5, so you are well within an acceptable range. Improving air flow in the growing area will encourage transpiration where plants take up the nutrient solution enabling calcium to reach the growing tips. A small fan providing gentle air movement over the top of the plants will help with this.

Thanks Beth for the response. Yes I have read through the article that you sent out, but that still doesn't answer my question.

From what i have understand so far, based on what I read from the web article, there are few reasons that could cause tip burn
1. Nutrient solution is too strong
2. Low humidity and high temperature
3. Lack of Nitrogen and other micro nutrients

I think my case would be more likely is nutrient issue, but before I conclude that, i would like to understand more how does the hydroponic nutrient with different N-P-K ratio impact the EC that recommended by the website for a specific type of vegetable, so that's why i raise my question here.

For example now I have two types of hydroponic nutrient, one with N-P-K of 30-10-40, and another type of nutrient has N-P-K ratio of 3-1-2, as recommended in some of the website, the recommended EC for lettuce is 0.7. So preparing two different types of nutrient that I mention above, now both nutrient solution has equivalent EC of 0.7, use both nutrient solution on the same type of lettuce, how does it impact the lettuce growth? I think first i need to understand the N-P-K requirement of lettuce, but seems like I can't find much information on the web, maybe from there i can base on the nutrient requirement to do some calculation in order to get the answer.

By the way, i don't think i need a fan for my grow area, since the temperature and humidity are meeting the expectation, please correct me if my understanding is not correct, but I do notice the lollo bionda lettuce has the least tip burn issue, not sure is it because it is placed at the side of grow area where the side has the most air flow.

Thanks!

There are definitely differences in lettuce types and varieties that are prone to tip burn. The University of Arkansas is doing hydroponic trials of a wide number of varieties, but I have not found the research summary posted yet.

The EC (electrical conductivity) of a solution measures the concentration of dissolved salts in that solution. Each element contained in a fertilizer dissolves in the water and contributes to the EC value. The EC does not measure which ions are present, just the total concentration of dissolved salts. Commercial fertilizers generally have recommendations for what EC to expect when using various rates of fertilizer. So for example, a fertilizer rate of 100 ppm might be obtained when the EC of the solution is 0.7.


You will need to have an EC meter to accurately measure this value. You would also need to take into account the base EC of the water that you are using and measure that before you add fertilizer.

Here is an overview article on fertilizers used in plant production, If you have more specific questions, please feel free to send me an email at scheckelhoff.11@osu.edu.