Remains of fire - safe for soil?

[princescruffster]

When I took over my allotment last year, most of the top layer of weeds was removed and burned along with the turf underneath.   Is it safe to dig in the stuff that was left behind after the fire -  it looks like bright orange soil.

Thanks
Nicola

[princescruffster]

[kt.]

 At the end of each season I have my fire on a different part of my plot - to spread the goodness into the soil.  I dig in all the ashes after having a fire.  I rake out the large parts and remove old nails that may of been in any of the wood,  then spread it and dig it in.

[davyw1]

I riddle mine and keep the fine soil for carrot and parsnip mix, the rest goes on the garden