[pedro]

anybody know if the yellow clay subsoil can be worked and improved to becoming a topsoil ?

[Beanzie]

Yes, but it will take a long time along with the addition of copious amounts of organic matter and possibly some grit. Worth it in the end  

[freyaluck]

I have yellow clay as well, I personally havent found I can work it at all.  My best tip would be to add a couple of tons of municipal compost (can useually get it from your local council or tip) to the top soil to help improve that. This is what I am having to do as I have so little top soil on my plot .  Plus raised beds really help.
Carlie

[richyrich7]

anybody know if the yellow clay subsoil can be worked and improved to becoming a topsoil ?

Why ? how deep is your topsoil ?

 Double dig to improve drainage, break up a  pan/release nutrients.

[David.]

I have it about 450mm down, and it attacks my skin if I handle it and I have to soak my hands in E45 cream.

[Aunt Sally]

This is a good site for info on improving clay soil:

http://home.clara.net/tmac/urgring/faqsoil1.htm

Adding lime will flocculate (stick together) the clay particles and create better drainage too.