I know when growing indoors that anything over 15 liter pots is overkill...not 100% sure about outdoors tho... but autos dont need big pots like photo plants do.
edit: But hey man...I can be wrong so wait for growers with better knowledge when it comes to growing outdoors in soil.
I am a coco freak..lol
Justin
I think your statement needs to say, " Depending on the strain..." I'd say, yes, many autos would do well on that size pot, but, others won't get their full potential. Check breeder's info to get an idea what size your plants could be. After growing some autos outdoors in pots, I personally wouldn't use anything less than a 5 gallon pot. There's never too much soil, only not enough...lol!