Many gardening books blithely recommend, almost as a knee jerk reaction, “aged manure” as a primo amendment for soils in the home landscape. That may be true, but how many yardeners have access to this mysterious “aged manure”? The answer is very few.
Nevertheless, if you do live in the country and do have access to some manure, there is no question it is a valuable addition to your soil. However, that word “aged” is a very important qualifier. Manure is fresh for the first year after being produced by the cow, horse, goat or whatever. It becomes “aged” after a full year of sitting around in a pile. Fresh manure, when added to a garden with plants can actually burn the microscopic roots of plants because it is so acidic. That pH changes after that first year of sitting around and becomes a valuable amendment to the soil. Earthworms and soil microbes will love a meal of aged manure. When it is available we spread it on our beds and around trees and shrubs in the late fall and then cover it with mulch. By spring, it is being worked into the soil by the soil critters, and the plants will begin to benefit as the spring goes on towards summer.
Commercial Dried Cow Manure
You can buy bags of dried cow manure at most garden centers and farm stores. This material is usually used as a fertilizer rather than as a mulch although it is a perfectly legitimate addition to the menu of your earthworms and soil microbes. Composted dried cow manure is till valuable, but not so tasty for the soil critters.