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What is the limiting factor in plants growing and production speed given that all nutrients are adequate in the soil.

Some factors I can think of:

  • intensity of light
  • concentration of CO2 in the air.

Some ideas to fix both: you could place reflective surfaces near a your crop. In case of greenhouse, you could also raise CO2 levels with a CO2 generator. Raising from current 0.04% to 0.5% (12.5x increase) does not require a lot of combustion.

I haven't seen anyone doing this. Why not? What are pros and cons and caveats?

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    Heat and water are also two important factors. Note: some plants (e.g. tomatoes doesn't like too much heat, e.g. over 30 degree centigrade.). – Giacomo Catenazzi Jun 7 '17 at 10:42
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    and note: production speed is not equal better production. On many vegetables a high speed means also dull taste. – Giacomo Catenazzi Jun 7 '17 at 10:43
  • Do you have any data which veggies are tasteless when grown too fast? I mean, pretty much everything commercially available products are tasteless, just not sure why. I always blamed hydroponics. Perhaps I will post another question. – sanjihan Jun 7 '17 at 16:51
  • For the commercial product the main reason it is that they are harvested too early, so that they ripe during transport and various storage and ready to sell before their are over-ripen. Unfortunately this is done without sun. – Giacomo Catenazzi Jun 7 '17 at 18:09
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You haven't seen anyone doing this because it's only some professional growers who do it, or even can do it successfully, and generally only for large scale crops. Increased or stable CO2 levels can only be achieved in airtight or sealed greenhouses, though that does not mean without vents, using very expensive and very large equipment. Ultimately, it's all a question of balance; integration of factors such as levels of sunlight on particular days will mean more or less CO2 supplementation is best, so its a complicated balancing act. The ultimate limiting factor, if you got all the factors such as light, warmth/cold/, soil ph, CO2, nutrients, airflow, disease prevention, will always be the genetics of the particular plant, meaning that, as a simplistic example, a tomato plant will never grow so big as a shrub, it will only ever grow so far and fast as it's programmed to, even under optimum conditions. Some reading here which demonstrates some of what's involved http://www.omafra.gov.on.ca/english/crops/facts/00-077.htm

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    Just to add. CO2 has high cost on safety. Sometime devices fails, so it could give a toxic environment (for human). [look for CO, or just high concentration] – Giacomo Catenazzi Jun 7 '17 at 10:45
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    Its not something I'm recommending @GiacomoCatenazzi - there's a reason why its only some professional growers that do it, its not something an amateur should attempt as far as I'm concerned. – Bamboo Jun 7 '17 at 10:47
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    The genetics can also be and are, as a matter of fact, altered. The only limiting factor is the human's lack of self-control when altering things it doesn't understand and cannot ultimately control. – user10810 Jun 7 '17 at 12:33
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Good discussion but I find it interesting that none has mentioned the pH as one of the most important limiting factors. The availability of inorganic carbon for photosynthesis tends to increase with greater pH. The pH also affects plant nutrient availability. Plant uptake of certain nutrients may become restricted and thus plant yield may be reduced. Over to you.

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