Most annual weeds need sunlight to sprout. If you let the pigweed sprout, THEN cover it, you might kill some of it.

The clear plastic works, but you have to make sure the weeds are well watered to lure them up. And it takes a chunk out of your growing season because it has to be sunny enough to get the temps up to "hot compost weed kill" temps.

I use a hoe, but I think it would depend on how large the beds or rows. I tried using a plastic billboard signs to smother out weeds, it was somewhat effective, but like lazy garden said it takes a while to really kill off anything.

D Chall ... "So nobody uses a stirrup hoe to scrape the weeds or loosen the soil exposing the roots?"

Well, all that using the stirrup hoe has done for me is expose MORE WEED SEEDS to sprout.

I've been using black plastic continuously for many consecutive years in high tunnels. I try to cover every inch of soil.

But in spring when I get ready to renovate there are always many weed seedlings emerging.

If you use a tarp I would not do it on a fallow year but plant through it and use it to suppress in-season weeds. Naturally you would need to get water to plants for wider covers.

I use plastic every year. I prepare my beds to plant and water them for 2 weeks. When the weeds pop up, I cover them. Then just check periodically to see if they are dead, usually doent take long. Then I remove it and plant my seeds. Where I am its hot and dry so I mulch my plants with straw, which typically blocks any remaining weeds.

A couple of points that might be informative.

First, tarping can work very well but it does take a month or so--just plan for it. BUT, be careful to use the right tarp! My first attempt was a real disappointment. I used it over lawn grass which almost died but not thoroughly. Then I thought to hold up the tarp to the sun. As tight as the weave was it still let through some light and that is all it took to keep the grass alive, half dead but alive.

Second, as to flame weeding, it works very well, too. However, a lot of folks mistakenly think you use it to burn weeds. In fact, you slowly move over them until they just wilt. You can see it very easily. Overnight, or at least by the second day weeds will be dead and brown. Usually I need to go back and catch a small weed or two that I missed. I let all of them compost in place to save time.

I use plain cardboard with mulch over it. Takes awhile but if I want to plant I cut a hole in the cardboard.