hello W,
I think there as many answers to that question as there are people gardening , I don't use chemicals at all , you may just as well buy your veg from the supermarket with all the chemicals they have in them if you do ( thats just my opinion), but there are lots of different ways to get rid of the grass. You can cover the area with something like cardboard, old carpet , thick black plastic or even a thick mulch . Leave that over the winter and in the spring remove it or dig in , depending on what you used . You can also do what has been done for hundreds of years and dig and turn it in , in other words do what ploughing does to it !!! When starting a new veggie patch you really can't beat the old way of double digging ....It really gets the ground dug deep and mixes all the minerals etc throughout the soil . It gives the bed the best start that can be given and allows for excellent drainage and allows you to remove all unwanted stone and to add any manure ,compost or whatever you want right from the start . I am not an advocate of starting a veggie bed off with just a rotavator as, unless it is capable ( and lots aren't) you won't get much depth , 4"-6" maybe ?, and it will be very expensive to do with the cost of fuel now. Double digging gets you down from 18"-27" depending on how efficient and thorough you are. Your local soil type and condition as well as the water table , will dictate how deep you can go , but in general , the deeper the better. Double digging only really needs to be done once or maybe once every 5 years or so , so you won't need to do it every year. I can bore for the UK on this subject , but hope that the above is of some help . If you do dig by hand , just do small amounts if you are not fit , and don't try to use a huge spade or fork , a small ladies or border fork/spade would be fine (thats what I use !!!) .
cheers for now
Russ