[zsellera]

that's per a single tomato plant, summer time. I guess it's the same for any greenhouse crop, see the reasoning here:

water use is necessary to manage internal climate. the greenhouse was designed to keep heat inside. the plants have to cool themselves (hence the environment) by evaporation. the farmer manages evaporation rate by watering, temperature and humidity. there are many feedback loops, both negative and positive, balancing it is a non-trivial task.

btw. there's an average of 1.2-1.3 plant/m2 in most tomato greenhouses I've seen.

[mrmuagi]

Ah, thanks for the clarification. I was shocked at how large a number it seemed, but I only factored in how much water the plant itself displaces in its structure, not the maintenance water to maintain humidity, temperature, etc.