Many organic materials provide excellent sources of nutrients. Composted sewage sludge, poultry manure, cow manure, composted leaves and other vegetation, peat moss, sea weed, and fish emulsion are all organic sources of nutrients. The problem with using organic materials as sources of nutrients is that the content of available nitrogen and other nutrients is often unknown. The level of nutrients in unprocessed organic materials, bulk sources, or organic material produced at home is anyone's guess. You may not apply enough fertilizer to get the desired result, or you may over-fertilize, causing nitrate leaching, salt toxicities, or excessive vegetative growth to occur.
Organic materials can be excellent sources of nutrients.
Be careful applying organic materials when the fertilizer analysis is unknown. In order to make a decision about which fertilizer to purchase and how much to apply, it is important to know why you are fertilizing. For shade trees, you may want to promote rapid growth so that young trees quickly become large and functional. Or you may want to maintain the health and appearance of a mature tree. An additional reason for fertilization is to rescue a declining tree.