"Chris" wrote
I want to get a fine tilth for sowing parsnip seeds - and the ground is
hard as iron ... not baked clods ... but rather a hard smooth surface.
What can I do?

The recent rain should have helped a little but you will have to dig along
the row to break up the soil as much as possible.
Then get some old used potting compost, push a metal rod into the ground
where you want each plant (9 inches?) and run it around to make a conical
hole (parsnip shaped). Fill this hole with the old compost and plant three
seeds on each hole covering with some more old compost. Job done.
If more than one seed germinates at each station then pull out the weakest
leaving just one.

Although the soil on our allotment is not pure clay, it's fine Thames silt,
it has gone solid over the winter, especially where we had a thick layer of
horse manure dug in for the spuds last year. I'm digging it and breaking it
up as much as possible then using the rotovator to break it up further, but
a fine tilth it is not!
We have resorted to planting our parsnips in Rootrainers and will plant them
out idc.
I'll have to go see the local mushroom farm to see how much they charge for
a good load of their old compost, might help stop the ground compacting over
winter again.
--
Regards
Bob H
17mls W. of London.UK