Commercially available insect manure, cricket manure, is relatively nutrient-rich. Poultry manure is relatively high in nitrogen, phosphorus, and potassium. Composted sludges are rich in slowly available nitrogen. If industrial wastes are included, contaminants, such as heavy metals, are present. Though approved for vegetable gardening by the Environmental Protection Agency, these fertilizers are not acceptable for organic gardening.
Worm castings are similar to compost in their composition and are equally easy to produce at home.
Among other benefits, organic matter helps soils hold water and air, makes nutrients already in the soil more available, and helps prevent diseases. Don't spurn organic fertilizers that are low in nutrients, because they're rich in organic matter that turns to valuable humus in the soil. Here are the 15 kinds of organic fertilizers found in garden centers and catalogs. Because organic fertilizers are so variable, nutrients and costs are also highly variable. Slow Copyright 2000, National Gardening Association.