[Goldfinger]

My onion crop this year is a disaster. 

They stopped growing when we had all that cold and rain, and when they did start growing again, either they bolted, or got mildew. [insert angry rude rasp']

I pushed the tops over to stop anymore growth a while back and have now lifted them to sort and dry properly.

My question's this....

They were planted in ground that was double dug with added manure so, should I lime the ground in the hope of killing off any mildew spores, but will it counter act the manure of this year now?

Or just weed and cover the ground with black plastic ready for next year, as I have no plans for that bit of ground until next year, (that I know of just yet).

[Goosegirl]

As you dug manure in earlier this year, liming should be no problem - don't know of it killing off mildew spores though. I'd not bother with weeding - just cover the ground with your black plastic.

[Trillium]

The manure and liming are no problem since good soil needs both, but I'd personally worry about  building more mildew spores by covering the area in plastic after the problems you've had. Mildew will normally die off with exposure to dry air, and if your soil happens to be damp/wet, then you'll increase your future headaches. If you have a good dry spell and the soil dries off somewhat then the plastic would work.

[madcat]

my solution to the same problem ..  plus a little onion fly  ... (hopeless shallots as well - pickled onions are going to be thin on the plate this year!) was to clear the patch of the weeds (how did that many get there?    ), lime it thoroughly and plant brassicas (sprouts, PSB, savoys, kale etc) for the winter.  They will like the manure, love the lime and all the space between the baby plants in this weather will give the sun chance to kill the mould spores.

I'll tell you in the spring if it worked!