[rowlandwells]

 I've had this problem on the allotment for several years now so much of a problem that I decided to go with raised beds this season we found we had better results from raised beds

so back to soil capping we have two plots around an acre in total both suffered from soil capping so one plot was devoted to raised beds at least half the plot has raised beds [20] but we needed to keep some open ground for our potato crop  beans and onions

so we kept I plot open and the other half of the other one open to  we tried a lot of things to try to stop the soil capping with little success there was even an article in which gardening on soil capping and they to  had resorted to the raised bed system

so after thinking of what would stop soil capping I struck on the idea of plastering one plot with horse dung that I had so I went with that s.....t or bust and it worked after covering the plot with horse dung prior to ploughing it
in to overwinter come spring it cultivated down lovely and has been very good loose soil over the summer months

growing has greatly improved no signs of any ground capping so I'm going to do the same on the other plot when I get my potato crop of the other plot  will be potatoes next season so after cropping that will have another plastering of horse manure hopefully fingers crossed this has solved the soil capping problem

[Goosegirl]

Anything you can get to loosen the soil texture will really help. I have alluvial silt about 5" below the topsoil so made raised beds, forked in grit and manure into the bottom trench, backfilled with the soil plus more grit and manure, then every year I top-dress them with lots of mushroom compost which also contains lime to aggregate the soil particles giving better drainage all round.

[ptarmigan]

I tried something suggested on here where I had a vacant bed. Covered with some compost then laid big sheets of cardboard down on it over the winter.  Soil was beautiful underneath when I lifted it next spring.  The  cardboard was a bit soggy and went on the compost heap.

Also used green manure over the winter (though watch out for the brassica family ones that aren't great if you have a clubroot problem) and that made a big difference.