SS, this is what I am planning to do on new allotment, currently a grass field. There are unlimited wood shavings from a nearby factory which are going to go on top of the cardboard on top of the newspaper on top of the tussocky grass. I am worried about them blowing around so might nail some netting down over them with U nails.
It sounds quite time-consuming, but almost anything is better than digging into dried out concrete.