Never grown it but i would start low at EC 2-2.5 and gradually ramp it up until you reach EC 4.0 or see some burn. The only decent info i could find does have pics so EC 4.0 is obviously working ok for the guy in Thailand. Might be worth an email to ask what nute make up he uses.
http://banraitubtim.com/blog/2013/12/growing-chinese-kale-chinese-broccoli-kai-lan-soil-less-system/

This post was edited by hex2006 on Wed, May 28, 14 at 8:07

Thanks Hex we must be on the same wave length as this site was the one that I also found. I will do as you say and let you know what the outcome is. Strange such a popular chinese vegetable , and grows well in hydroponics , and is a staple in nearly in every asian restaurant.

Hex thank you for your comments I just received a reply from Thailand re the growing of Kai Lan or Chinese Broccoli. the following is a cut a paste from the person in Bangkok
I germinate the kai Lan on a sponge with only water. When it germinate, we keep it in plain water until the second week or when the real leaf starting to come out. Then we used .8 EC, until the root is long enough to about 2-3cm or so. this is where you have to judge when to move it to the grow table. I usually look if the leaf are strong. from germination time, this may takes upto 2 weeks.

In grow table, some other farm use only 2-4 EC, but I found it turning the leaf yellow. In the summer, like now, I have a hard time adjusting anything. My nutrient tank is measure over 36C some time. from my experience, we need to low EC and increase the PH. So this month, my Kai Lan table is at 4EC and PH=8-9. Why? Water evaporation is really high in summer, if your nutrient is too concentrated, it will shock the plant due to the amount of liquid passing through the plants.

I am in the process of converting all my tanks into one single big tank to lower the over all temperature. Hopefully down to 30C and 32C day time.

In theory, the plant uses food from the seed, until it is big enough to require outside food source. So you will have to judge when you need to be EC=0, EC=.8 and EC=4-5.

Thanks for posting the info mate. Battling 36C res temps cant be much fun for him but compensating for the evaporation by using low EC, high PH is a sound approach as PH tends to drop as the EC increases.
I do the same with aero, the droplets get smaller from the second they are created and theres not a lot of water in a 50 micron droplet to start with.
Most aero users are aware of the lower nute strength requirements (typically 1/8-1/4 strength) but not many understand the reason. Even fewer will consider the PH shifts that accompany droplet EC increases due to evaporation.