Agronomic and technological approaches to minimizing gaseous nitrogen losses from croplands

Abstract

Nitrogen is transferred in gaseous forms from the earth’s surfaces to the atmosphere through NH3 (and probably amine) volatilization from soils, waters, and plant leaves; N2, N2O, and NO evolution during biological denitrification; N2, N2O, NO, and NO2 evolution during abiological denitrification (chemodenitrification); N2O evolution during nitrification; and NH3 and NO x (N oxides) release through combustion. The physical and biological processes (except burning) leading to these gaseous N transfers have been discussed in the preceding chapters of this monograph. Discussed here are some approaches that have been or are being taken to minimize gaseous N losses from cultivated soils. These approaches seek to improve the efficiency of soil and fertilizer N use by crop plants. They include use of chemicals that inhibit biological activity in soils, amendments that alter the physical and/or chemical properties of N fertilizers, and improved crop and soil management practices. Some of the methods directed toward reducing gaseous N loss from cultivated soils also may increase the efficiency of plant use of N by decreasing the movement of inorganic N in solution from the plant rhizosphere, or by regulating the form and amount of N being supplied during any given growth period. Discussion of these latter aspects of N use efficiency is beyond the intended scope of this chapter which focusses on methods of reducing gaseous N losses from fertilized croplands.