Thanks for the thoughts. It may be that Janet has hit on something, compost is more intimately mixed in loamy soils, in clay if applied a short time in advance it tends to form pockets. There are some worms in the clay but not as many as I would have expected in the loamy soils. Chlorosis does not seem to be a problem. All the vegetables seem to green up well.
As for overwintering, there are some small onions -set size -left in the ground. They have sprouted and rather than pick them as spring onions I'll leave them in the ground and see what happens.
A raised bed and polycover seem sensible ideas. Jen is pressing me to put raised beds in the vegetable patch to tidy it up and make management easier. I could kill two birds with one stone.
Regards
David T
"Leslie" wrote in message ...
I would suggest that you try some over wintering onions the sets are still available and the ground still warm, also the trees will not shade the onions without the leaves, they will have a good root system come the spring and be off like rockets.

........................Leslie
"david taylor" wrote in message ...
I grew onions for over 20years in Cheshire on loam in 2 locations. Sunny position, pH about 6,moderate amount of manure, about 1oz/square yard of growmore.
I had good crops and enough onions from 150 sets to last a family of 6 through to April/May from August.
I am trying to grow onions in Devon on a clay patch surrounded by trees. I apply horse manure, pH is about 6-I dressed the vegetable plot with lime last winter, I use growmore at the same level as that in Cheshire.
A lot of the sets hardly grow at all and the largest onion is about 4 ounces. Some go to seed early, but much of the plot becomes shaded by trees after the end of July.
The local weeds-red campion especially are very active and I have to work to keep them down. In spite of this the crop is very poor and only lasts my wife and I through to mid November.
Any helpful thoughts please.
Regards
David T.