Tilling brings buried weed seeds to the surface where they sprout. You have to cover the soil where there are no crops growing with mulch. Mulch has to consist of more than a couple layers of newspaper, 3 or 4 layers are okay but then cover with wood chips, wood shavings, or seed free mowed grass, or straw. Some people use black or red plastic, others use landscape fabric, and some people use landscape weed blocking paper. Oh, cardboard and old carpet work too. Cardboard can be tilled under at the end of the season but carpet has to be removed.
And no matter how much you mulch you still have to pull or hoe weeds. And no mulch will keep perennial weeds from coming up, especially Canadian thistle. It will come up through round bales of hay.