TEKNIK wrote: ↑Sat Jul 06, 2019 8:44 pm
From my limited understanding of co2 intake and maximum micromouls it is in direct relation to the spectrum.
Plants that receive sunlight in a green house can take more micromouls before co2 is required.
Under artificial lights I am pretty sure 1000 micromouls is maximum before co2 is required to go further.
There is probably a high chance that artificial lights have a more focused beneficial spectrum so although sunlight is able to hit the plants with more it isn't doing anything that is beneficial, the plants may just regulate themselves differently under the broader spectrum.
More research is required but I pretty certain there is a way to increase productivity without co2 and just with a different spectrum.
Sunlight is not only direct light a good part of it is diffuse. In greenhouses the pro's always use diffusing materials cuz diffuse light yields up to 12% higher compared to direct light. Diffuse light eliminates shadows and it travels much deeper inside the canopy. So the diffuse light is one of the factors why plants outdoor develope better. On cloudy days all the light is diffuse and as long as the temps stay high enough the photosynthetic rate stays almost the same.
Sunlight is also not constant, the intensity goes often up and down because of clouds.
Bad thing for us, we lose at least 6% of the light when using diffusers in front of our diodes. Even the best pmma materials have only 94% trasmission rate and as soon as we use a higher haze factor the transmission loss gets even higher.
Pretty sure you know fresnel lenses. Such fresnels could be used to focus the light on a certain surface area and get more diffuse light in the same time. Even if we lose 6% intensity the diffuse light could maybe compensate that. They would also improve the color mixing when different diodes are used and would reduce dazzling effects and help to get a more uniform spectrum.
The tomato plants in greenhouses are often +10m high and there is only 1m in between two rows of plants. Without diffusing cavity-plates the fruits on the bottom of the plants would not get enough light and they would yield much less.
Outdoors you always have diffuse light also when there are no clouds. The air is full of dust, vapor and other small particles and these also have diffusing effects.
Another reason why plants outdoor develope better is their root system at least when they are transplanted directly to the ground. The bigger the the root ball the bigger the plant. Always if you see 4-5m high monster plants with 5-6m perimeter they either have huge pots or are planted directly in the ground. Root temps also stay almost constant no matter if its day or night. The ground keeps the heat long enough so it swings only by 1 or 2° between night and day and that only on the grounds surface.
The wind outdoors also helps the light to travel deeper and the evaporation is much better distributed over the whole plant and not only focussed on the canopy like indoors.
The heat is also not only concentrated on the 1st few inches of the canopy. Outdoors the surrounding heat is almost the same from top of the plant down to the bottom.
All this things have effects and are different from indoor conditions. We can only try to keep a good balance between temps, humidity and intensity. Outdoor this happens almost automaticly and even under bad conditions the plant can adjust themself. If indoor only one of the 3 aspects change it immediately affects the photosynthetic rate.
IMO the best way to increase yield/m² is to go into the vertical and add a 2nd layer of plants and another light. With LED strips we need only 36"/1m of total heigth when we use cuttings and veg them less than a week. 8" high pots and strips mounted on U-profiles would still leave 30" free space for the plants in between. Enough for the most strains..
I've helped a friend to build two 350w strip lights for his 4x 4' tent(10pc 4ft EBgen2 strips + HLG-320H-20A). He has two stacked areas now, each with 36pc 1gal teku pots with coco and he regularly yields a pound or more from each light. Thats +1kg every 8-9 weeks out of a 4x 4' tent. Even outdoor plants can't do that in the same time..