I've got a load of cardboard (house move) and this years supply of muck on its way to my new allotment plot. About half of the plot is currently under black plastic and likely to stay that way for the first year as I know my limitations. The muck is pretty fresh. Can I put down the cardboard on grassy/weedy areas and put the muck on top? The theory is that by autumn or next spring, the cardboard and manure will be rotted enough for cultivation and the weeds below will be dead. Any thoughts?