Soil water absorption

Unless you are trying to do a super stealth grow or want one of the Worlds smallest cannabis plants, a half litre pot is nowhere near enough room, a 10 litre pot should be a minimum for an auto outdoors. Anyway, to solve your current problem, sit your pot in a small pot of water so that the soil sucks up through the bottom of the flower pot. Fill the pot so that the water comes about half way up the flower pot and wait until you can see moisture at the surface of the soil inside the flower pot. You may need to top up the soaking pot if all the water gets sucked up too quickly. After this, in future when you water, always water to run off, that is, water coming out of the bottom of the flower pot and this will prevent your soil from becoming "hydro-phobic" once again. Hope this helps, Organoman.