Manure is any substance produced by animals or plants that is used as fertilizer. Most manure consists of animal waste mixed with straw or hay from barnyards, though it may be pure animal waste. This waste is collected and spread onto fields. When it decays, it releases important nutrients that enrich the soil and aid plant growth. Manure also loosens the soil and improves its ability to absorb water. A special kind of manure called green manure is obtained from plants that are plowed into the soil and allowed to decay.