Nitrogen Release from Land-applied Animal Manures

Abstract

Animal manures are a valuable source of nitrogen (N) for crops. However, not all N in manure is available to plants. In general, manure N in inorganic form is immediately available to plants, although some inorganic N may be lost through ammonia volatilization and denitrification, and some may be immobilized by microorganisms. Another fraction of manure N available to plants is that proportion of organic N that is mineralized within a crop’s growing season. This mineralized N is also susceptible to losses through ammonia volatilization and denitrification, and to immobilization by soil microorganisms. Thus, to determine the correct N-supplying capacity of animal manure it is necessary to know the amounts of inorganic and organic N present in the manure, the fraction of organic N that is mineralizable, and the magnitude of processes that decrease the availability of released N.