The guys next to me are fine-tuning an automated watering system for window plants on a Raspberry PI, and they are having some issues with the humidity sensors. They don’t work very consistently. Well, the reason why is quite clear. I just suggested an idea to them – to place the plants on scales and water them when the weight drops below a certain value (meaning that the soil is drying out).
And from there, an interesting discussion ensued. What contributes to a plant’s mass? After all, trees grow, taking mass from somewhere. Where from?
There are few options: soil, water, carbon dioxide. What decreases and in what proportion? If a plant gains a kilogram in weight, by how much should the soil get lighter?
PDF on the topic http://www.eurohydro.com/pdf/articles/gb_plant-food4.pdf
Hi, I'm Rauf Aliev. 