ABSTRACT
Acknowledgments ..................................................................................................................... 186
References ................................................................................................................................... 186
Nitrogen is considered a key factor in agricultural production and in soil systems not only
because most crops require and accumulate more of this nutrient than any other, but also
because N can be lost from agroecosystems by various paths, due to natural processes but
also through agronomic practices. These can contribute not only to erosion and leaching,
which affect also other important nutrients, but losses also occur in gaseous forms (NH
,
N
O, and N
) via volatilization of ammonia and denitrification. Providing and replacing
nitrogen in various inorganic forms is a costly matter for farmers, and often there are
supply, logistic, or other constraints also making it difficult for farmers to provide
sufficient N for their growing crops.
