I think everyone's allotment has some tricky aspect, and in my case it's that I'm kind of sliding over the top of a hill. That means there's a definite slope from side to side, and also from one corner to the other - and that's creating all sorts of problems now I'm getting into the corner that's lowest of all.
The trouble with slopes is that you get such a massive variation in the quality of the soil, sometimes within a few feet.
On my allotment, the top area of the slope - on the relatively flat top of the hill - retains soil, so has plenty of topsoil and is easy to dig over, and also drains well, so it's nice to cultivate right from the start.
As you get lower down the slope, though, all the topsoil gets gradually worn away by the rain and groundwater flowing down underneath it. So you end up with a gloopy mess of stones and subsoil which is no good for anything. It's horrible to dig over, it's boggy and muddy this time of the year, and it takes a good couple of years of adding muck to get it in good heart.
My universal solution to all this is to put in raised beds - and so far they've paid dividends for the extra work involved. I've stripped off the turf from a really horrible bit of the allotment today, and it was actually sucking as it came up. There was also more bog-plant and weed than grass, a sure sign that the soil is really cruddy there. I'll put a 9" high raised bed of scaffolding boards over it, shovel in as much manure as I cram in, and by next summer I should have some halfway-decent crops out of it!