A direct calculation based solely on light is not possible, light intensity is a significant factor influencing a plant's water needs.
Photosynthesis drives gas exchange which which drives transpiration. 90% water is used for transpiration roughly 10% cooling.
Rate of transpiration dictates rate of water and nutrient uptake/cycle.
The environmental factors that determine photosynthesis are not the same environmental factors that drive transpiration. Although there is crossover with temperature.
Plants use light for photosynthesis. More light generally means more water is transpired through the leaves to cool the plant and transport nutrients.
Plants in brighter areas may need more frequent watering compared to those in shaded environments.
Temperature, humidity, and soil type all influence how much water a plant needs. For example, warmer temperatures and lower humidity will increase transpiration, while well-draining soil will allow for better watering.
The best way to determine how much water a plant needs is to observe it and consider its environment. Look for signs of wilting, yellowing leaves, or dry soil, which can indicate the plant needs water.
Thoroughly water the plant until water drains out of the pot, and let the excess water drain out. Avoid overwatering, as it can lead to root rot.
Plants in brighter environments generally need more water due to increased transpiration (water loss through leaves). Other factors like plant size, temperature, humidity, and soil type also play a crucial role.
Leaf transpires 3x the rate at 86f as it does at 68f.
Synthetic and organic fertilizers have different effects on watering needs and soil properties like Cation Exchange Capacity (CEC). Synthetic fertilizers are generally quick-acting and water-soluble, requiring more frequent applications and potentially leading to leaching if overwatered. Organic fertilizers, on the other hand, release nutrients more slowly and can improve water retention and soil structure, reducing the need for frequent watering and decreasing the risk of nutrient leaching.
There is no right or wrong answer only understanding the different nuances of growing in different conditions. Understanding the differences in your own setup based on what you look to achieve weighed against your time constraints and climate you live in, approaching watering with the idea one way fits all is a sure fire way to run into problems eventually down the road.
In nature there is no water everyday at 6am. No fixed schedules to run on.
It's ideal to create a day night cycle that ensures early morning watering every day or 2nd day. Generally you want to ensure by time the night cycle comes around the soil is not oversaturated but not dry, a large portion of a plant's phosphorous will uptake in early hours of nightfall, I read anywhere upto 51%, ideally you want optimal soil conditions as oxygen plays important part in P uptake along with root respiration.
Conditions that occur for transpiration during the day do not occur for nighttime respiration, with no latent heat, evaporation and evaporation alone will dictate if any water leaves pots at night, if the pot is left oversaturated overnight or oxygen is in limited supply or rh runs above 70% then the plant cannot process the energy harvested during cellular respiration that days light cycle the energy will remain stored in the stems.
Water water water till ec tells you to.
You should irrigate your plants until the electrical conductivity (EC) of the leachate (water that drains out of the growing medium) indicates it's time to add fertilizer. EC is a measure of the salt concentration in the water, and it can be used to determine when plants need more nutrients.