It sounds like a meadow grass but even with couch there will be no problem. There seems to be so much information to take in, but its really quite simple as long as you follow some rules.
I would go with card first but not one layer which is overlapped by a few inches – but go with a few layers. Overlap the card of the first layer by 6 inches and then add another which overlaps the first one 50/50 and lay it so that it overlaps its neighbour by 6 inches.. add a third layer in the same way.
It seems like a lot of card but if you’re innovative you can get a lot of clean card very easily. We’ve made 75% of a large allotment by this way and have a very large pile of card in the garage still. Local technology parks are a great source of card, we’ve acquired all of ours by this way.
You have plenty of time and with 6 inches of rotted manure to cover the card – you’ll definitely be growing this year. Plan to grow from modules as your manure might still be a little ‘lumpy’. Spuds, beans, courgettes, marrows and salads will be easy crops in the first year. Our allotment was 5′ high with weeds, we cut it all by hand and were growing again in a month, salads, leeks and plenty of salad.
Try to skim off your paths and add card too if possible, you can do this in a couple of months time. Pull out the worst of the root from the layer that you’ve skimmed off and put it back over the card and expect to hand trowel out stubborn offenders frequently if necessary.
we’ve employed this on the worst offender of all – Horsetail and there is little getting through. Where there was no Horsetail, there was couch, buttercup and dandelions, that’s largely all gone too except for some ‘edges’
Good luck