Growing on site that previously had chickens?

We have recently got an allotment but a third of the area used to have chickens and has thick black soil.  I am assuming this will be too rich to plant in for a while, but don't know how long?

One idea we had was to dig up some of the rich stuff and swap it with some turf we have got to dig up elsewhere and put the turf upside down over the original chicken area and then dig it up later in the season for use next year???

any ideas?

If the soil is black, it can be used now. If it's also thick, then you could easily spread it where needed but I personally would never 'waste' it by piling turf on top of it. Fresh manure would do a better job for that task. And as Aunt Sally says, try to test it to see where you stand pH wise.