Cupcakes - If you want to put horse manure into the soil around crops in beds, you need to leave it to rot. I have been trying to read up a bit on this to find out why. Basically, it seems to be all about decomposition, in particular the magic that happens when things decompose in air.
Here's what I found out so far: if you put fresh manure directly onto plants, the decomposition process is different. Firstly, it can release ammonia, which will scorch plants. It can also be full of salt, which is not a good thing when you're repeatedly adding it each year. And (at a practical level), it can contain weed seeds because it hasn't got hot enough to kill these off.
However, here's the interesting part: as I am sure we all remember from the nightmare of learning the nitrogen cycle at school (trigger warning: flashbacks, traumatic memories of science exams) N is constantly transforming into all kinds of compounds. It appears to be the case that plants can't access the kind of nitrogen you get in fresh manure (it tends to get lost as the aforementioned ammonia or as nitrous oxide): it's only as its decomposed that it gets mineralized, which means that the nitrogen gets converted into forms that plants can use (i.e. nitrate).
From what I can make out, it's the aerobic bacteria that do this. Anaerobic decomposition leaves you with loads of stuff that plants can't use - and some stuff that is actually toxic to them! So if you get a load of fresh manure and make a big pile and turn it regularly, it seems you'll get more of the good, water-soluble nitrogen and nutrients that make plants grow.
(I still want to know more about the details of all this!)
I dig my manure out of a very waterlogged pit, and I have a feeling this is why it didn't give my plants such a boost as I expected last year. So I'm going to get it some months in advance and make sure it's more aerated in future.
However, I think you can use fresh manure to make a hot bed - did you see Gardeners' World this week? Monty did one for something (I forget what the plant was) exotic. You basically knock together some kind of a frame, and pile the horse poo up to quite a depth - a couple of feet or so - then cover it with 15-20cm of soil. As it rots it gets really hot, so plants that like warmth - like billions of tomatoes from armpit cuttings, for instance
- are happy. Then when it is well rotted you can put it on beds. So you get two uses out of it!
ethel - HOORAY for mattocks. I am a big fan. I use mine more than I ever thought i would, including to chop through some gigantic ash roots this weekend. It does feel like a kind of Buffy-style initiation ceremony to wield one.