Hydroponic Tomatoes and light spectrums

Hi,

Fairly new to the forum, but I really need some hydroponic / lighting advice.

Unfortunately ALL the information on hydroponics on the internet is to do with cannabis. I just have a few micro-management questions about tomato growing that I cannot seem to resolve.

My tomato plants have been growing under CFL 6400k lights (daylight bulbs I believe..) now for around 30 days... I have flower "buds" beginning to form on all of them, and they are all around 30cm tall.

I have read that 2700k lighting (warm white lighting..) should be used to flower them, or should be used whilst flowering.

What I am struggling with is WHEN to make that change over from 6400k to 2700k spectrum. Do I do 2700k WHILST flowering, or do I do it before to encourage flowering?!

I do not own, nor wish to use HID or MH lighting.

Secondly, when should "bloom" nutrients be used.. again, when should the change over from veg to bloom nutrients be made.

Any ideas?!

Thanks in advance.

 

Hi tahsocks - thats sounds a complex set up. I have no clue.

But what are you doing? Is this a commercial venture, or are you doing it for fun?

I have a light box in which I grow seeds and cuttings. So I have read up a bit on lighting on the net, but don't profess to know much. To me, a lot of it comes down to economics. I read about different spectrum lights and how you should have the right lights for growing. But the best growing light is the sun, and the sun doesn't have a specialised spectrum - in fact its a very smooth wide spectrum. So my own suspicion is that if you can reproduce the wide spectrum of the sun plants will grow well. In my lightbox I have used ordinary household fluorescent tubes and found that plants grow and flower perfectly happily. I use a light meter to ensure that I have a sufficiently high intensity of light, but otherwise I am not convinced that I need special tubes.

As I say, I think a lot of it is to do with economice. It could be that a special tube would allow me to use a lower light intensity and wattage, and hence save money - but that has to be set against the cost of buying a special tube. But for me the best economy is to have an enclosed light box and make sure that the light level is high by ensuring that no light is lost. In the same way that if you want a high temperature in a room or house you must insulate it well to ensure no heat is lost.

 

OK, well, obviously the sun is better than any bulb however that is not my concern.

I'm hoping to grow my own tomatoes and other vegetables hydroponically throughout the winter, just a hobby really. So it is not too late to start growing (: they are already producing buds and hopefully tomatoes soon!

I have just read on numerous sites that red spectrum bulbs are needed during flowering... hence my original question.

Thanks anyway. I suppose I will just have to see...

 

Tahsocks. I don't think it is strictly true that red spectrum bulbs are needed during flowering. Any light source will give out a spectrum that includes red light. Consequently I believe that any normal light source will do as long as it is bright enough. If the comment was that red spectrum bulbs are more efficient because they give out more of their light in the red area - the comment could well be right. Again I think it comes down to economics.

Incandescent lights give out a pure black body spectrum (ie a continuous spectrum of all colours), and are really closest to the sun in that respect. Consequently their light would be just right. However they are not used because they are more expensive to run - and there is also a heat problem which costs money to solve.

Fluorescent lights give out highly specific wavelegths of light from the mercury in them in the form of spectral lines with quite a bit in the blue area, but they also give out a wide spectrum (black body radiation) from the phosphors. This of course includes red light. So if you have sufficient intensity of light, you will get all the red light you need.

I have never grown fruit under lights, but I don't have any problem in getting plants to flower under ordinary fluorescent lights. However you do need a high intensity of light to get things to grow well (whatever the source of light). I aim to get about 10,000 lux at the foliage level - as measured by my light meter. This, of course, is quite a bit less that a sunny summer day, but it remains constant for 14 hours a day, whilst daylight varies through the day. 3,000 lux tends to be quoted as the minimum for reasonable growth.