Here you go Fin, I don't know why I'm trying to help you, you'll probably still try to use manure anyway.
The concept of "burning plants" is important to understand, and it involves a bit of chemistry.
Remember, in high school chemistry, the experiments about osmosis? This is where water with a high salt concentration is separated from water with no salt by a membrane. The membrane allows water to pass through, but not salt.
Water goes from a no-salt area to a high salt area by osmosis. This applies to any "salt," which by rough definition is a chemical, part positive and part negative, which usually dissolves in water. It includes not only table salt (sodium chloride) but many others.
Osmotic effects can also occur in the root zones of plants if roots are exposed to a high-salt concentration. It pulls moisture out of the roots and dehydrates the plant. This causes the same "leaf scorch" effect you would see in a summer drought. Leaves appear to be burned, and plants may wither and die.
All fresh manures contain large amounts of salts. This is the result of the normal intestinal function of animals. In manures, it is not the nutrients which do the damage to plants, it's the associated salts which dehydrate or "burn" plants.
Salts are greatly reduced in manures by composting for a few months. They are soluble in water and rainfall will wash them away.