No-one mentioned that manure should be well-rotted before use (except for roses that seem to like it fresh) as it can burn your plants with the nitrogen content in the urine.
Generally, as I remember from college, Chicken manure has the highest nitrogen content, then farmyard (usually cow or pig, but may be a mixture), and horse has the least.
Horse manure can be the best soil conditioner as it has lots of bedding mixed in with it, but it depends on where you get it. If picked up from the field or from a bare floor, it is pure and rots very quickly. The quality of manure from a heap varies greatly, depending on what the horses are bedded on. If straw, it makes a great addition to your soil or compost heap, but not many people use straw now. Wood shavings are far more common, and manure with this in takes much longer to rot down. If you use it too soon it can rob nitrogen from your soil. However, if you can get manure with shredded paper, shredded straw, paper pellets, (LIke cat litter), or Aubiose (shredded hemp stems), these are all excellent.
I know all this from working with horses, BTW, and always try to get manure when I can. Most stables will let you take away as much you would like to, as they have to pay to have it removed unless they have a local farmer who will use it on his fields. If you do go to get some, take it from the middle of the heap, as this will be lovely stuff, dark and crumbly, and not smelly, but it may take a bit of work to find. Personally, i find it much easier to go and muck out selected horses at the local stables! I choose the horses with the bedding I want, put it straight into bags and the build a heap at home, add some to the compost, and some to the bottom of pea trenches. I get my 'horsy fix', that way too!
Farmyard manure will usually have straw in it, too, but farmers are far less fussy and more economical than horse owners, so it will be more manure and urine than horse manure, and rots very quickly to a nice conditioner. You may be able to find a farmer who will deliver a lot of well rotted stuff, but you'll probably have to pay him for it.
My landlady and friend who lived here before me (vegetarian, and went off to marry a beef farmer-huh!), kept chickens here in a 16'x10' pen. I turned it into a rasp cage 4 yrs ago, and WOW. The combination of muck, their scratching and eating everything gave me the cleanest, most fertile, weed and pest free soil ever! What crops I had from yr 1, and no weeds until this yr (my 4th)! My biggest problem has been thinning the canes!
Who says I'm full of s***!!
I would love to know more about using comfrey and nettle feeds. How to make them and how to dilute them, and which plants each is best for.
And I heard somewhere about using LISTERINE, yes, you heard right, Diddy, against some pests, I tnink it was. Will get back to you on that, if I can find it.