Watering question

My seedlings are now 2 days old. They are auto ak47's. Im using canna terra pro grow medium. The plants are under a 400w dual spectrum lamp (run from a mh, hps ballast). The light was about 3ft above the plants yesterday, and moved closer (2ft) above them tonight. Didnt water yesterday as the soil felt moist, I did water today however as the soil felt dry to the touch. Basically my question concerns amount of water to use. I keep hearing that you should water till you get run off. Why is this? Basically I watered my plants untill it felt like the soil had the right amount of water in it, I gauged this on the speed of absorption - at first it seemed to drink up the water, then as soon as the water started to settle on top I stopped. Whilst doing my research on the growing medium I have I saw someone say that they didnt get much (if any run-off), so im pretty sure its not just me. Of course, if having some run off provides a necessary service to the plant then I will endeavour to achieve it - but for that im gonna need the genuine reason for having run off. So, anybody got any thoughts?

Water your plants thoroughly and allow them to dry.

By doing this you increase the rate at which your roots grow, they will eventually fill the entire pot to search for water..which is exactly what you want.

More roots in a pot means a higher rate of nutrient uptake.

Also, keep that light as close to your plants as possible.
A good rule of thumb is to put your hand under the light and hold it there, if your hand can stand the heat so can your plant!

Thanks for the reply. Im confident that I watered them thoroughly, but I did not get any run off. It seriously feels like id be flooding the little ladies if I gave them enough water to get run off.

The question still remains unanswered though - what positive benefit does watering till you get run off provide that simply watering well (but not getting run off) does not? Anyone?

You can test your ph of the water to see if you need to adjust anything. I also think that when you water until it runs offyou are flushing old for new.So you dont get chemical build up from ferts.

Watering until you get runoff will flush out anything left in the soil but apart from giving you 100% confirmation that the soil is completely soaked..

Thanks guys. That's sort of what I thought, nice to have it confirmed. I think il wait till they're just a little bit older and more established and then give them a proper watering till I get run off.

Ooops...posting to an answered thread..

guess I better go smoke another bowl, leave you folks alone

Gave them a proper watering yesterday, got some run off. Tested it, ph is bang on 7. Little ladies looking happier