[BarnBrian]

I saw an idea on TV years ago which I've yet to try.
In autumn dig a hole slightly deeper than a bale of hay in one of your greenhouse beds, throw on a good few handfulls of blood and bone and then plenty of water. After that cover with a few inches of soil.
It has the joint benifits of as it composts down it generates heat and also enriches the soil.

Brian

[PinkTequila]

I would imagine straw would better and cheaper for this.

[Robin Redbreast]

i would imagin the same quantities of well rooted muck would have the same effect.