Some gardening sources recommend watering lawn in the morning, with the reason being water is needed for photosynthesis, and the grass can use it straight away after watering. Some sources say the evening is the best time as the water does evaporates slower when it is colder and there is no sun, therefore the water has more time to soak into the ground. To make it even more complicated, there is an argument against evening watering stating that grass staying wet through the night may increase risk of diseases (see Watering efficiently) .
From a water conservation point, which is better time for watering, morning or evening? Was there some controlled experiments done, with grass or other plants, with the goal of maximizing plant mass growth with a given amount of water?
If the best time is confirmed to be very early morning (that would probably make sense from the reasons above, but experimental evidence would still be preffered), but I am unable or not willing to do that, which of the easily available options (morning, evening, or both - with the amount split between them) is the best?