[ex-cavator]

A related question from another newbie - should I put a membrane of any sort beneath my raised beds? I am reconstructing some old, tired beds on an allotment I've taken over, there's virtually no depth of soil left on top of carpets used as a membrane. I was going to dig them out a bit deeper, put a mixture of fine fresh soil, remaining 'worked' soil mixture from other beds, and very well rotted horse manure in to give me a decent depth to get started. But should I replace the membrane or leave it out - if replace, then with proper membrane, or will replacement carpet or newspaper do just as well?
Finally - I hear what your saying about carrots, but is there any other reason I shouldn't sow in recently manured ground - I'm not bothered what they look like, I just want to eat them. My main priority is to get two or three beds workable as I need to be planting stuff before it's too late, if I can put a few carrots in that'd be good but otherwise I'll wait until next season for them & concrentrate on stuff that likes manure.

[peapod]

Ive split this off for you ex-cavator 

[penance]

I think no. Putting membrane down will encourage capping of the lower soil when the bed soil is placed on top.

[mumofstig]

I hope you have lifted the old carpets, I know it is not easy but as they rot down they release chemicals into the soil, and they are banned on a lot of sites now.
Dig over, or just loosen with a fork, this lower soil level before putting your good soil on top.
Then your raised beds, without any membrane, will have a good depth of soil for you to gradually improve with your manure each year

[compostqueen]

I put cardboard in the bottom of my raised beds but only because I had weeds there and couldn't be bothered to hoik out all the weeds before I got cracking    The cardboard just rots down eventually

If muck is all you have to raise the level then you'll have to use it. It will slump quite a bit so you'll need to be prepared to top it up.  You can use home made compost, old compost from growbags etc, sand, leafmould and soil to add to your raised bed. If you get the manure at the bottom and all the compost etc at the top you should get some carrots    For carrots you need a fine tilth (which your muck won't give you) so you could mix some gritty sand with some soil to give you a fine medium for sowing your carrots in

[Trikidiki]

I have a very large goat willow tree on my plot which only had grass growing under it.

This winter I skimmed off about 10 inches of topsoil, then built three raised beds which are about 18 inches tall. I then tacked weed membrane onto the bottom of them and refilled with the seived top soil. The idea is to hopefully stop the goat willow roots coming up into the raised beds. They are being used as seed/nursery beds so I do not need a huge depth of soil.

All the other beds on my plot have nothing underneath. It would restrict root growth too much.

[digalotty]

i would make a trench and fill it witha half sand and used copost mix and put your carrots in that and as mentioned i would take out the menbraine and dig the bottom