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All fresh animal manure
All fresh animal manure should be left to age, or mature, for about a year before using it. When fresh, it is often called "hot" because the various acidic ingredients in it will "burn" (kill) plants. Mixing fresh manure into a compost pile might knock one or two months off that time, but this is not an exact science; it depends on other things, such as the other ingredients in the pile, frequency of turning the pile, the pile's moisture, even weather (compost ingredients don't break down well when they are frozen). Similarly, the matter of how much you use is less about the size of your garden bed and more about the quality of the soil. You need to check the soil's pH and, separately, the chicken manure's nitrogen. You can buy pH kits for a few dollars (max) at garden supply stores. You might want to consult the local cooperative extension about testing for nitrogen to see what other nutrients you need to balance it. Remember that different plants need different nutrients, so the fertilizer balance will depend on what you are going to grow. That said...if you are a beginner gardener and all of this sounds complicated, you could take a chance and use good compost in your beds, sprinkle and mix in a small amount (a surface layer, worked in) of chicken manure that is at least one year old, and fertilize with a mixture that has low-to-minimum nitrogen. Gardening is an experiment from year to year; no matter how carefully you calculate and measure, something could happen that is out of your control. (Think pests, disease, weather...) Take notes, plot your garden so that you can rotate your vegetables next year, and have fun!