Nitrogen fate and transport in agricultural systems

ABSTRACT: To sustain and maximize agricultural production in order to supply the nutritional needs of a continually growing world population, agricultural systems will need nitrogen (N) inputs. In its inert form as elemental dinitrogen (N2) gas in the atmosphere (78%), nitrogen does not impact environmental quality. But the extensive use of N in agricultural systems and the associated transformations of N into various ions or gaseous forms contribute to leaks from the N cycle. These N losses may contribute to the degradation of water, air, and soil in many regions of the world. When N is in its nitrate (NO3-) form, it is one of the most mobile ions in agricultural systems, and NO3- leaching is a primary source of the contamination in drinking water. Soil erosion that transports soil particles and N also contributes to surface water contamination. The gaseous transport of ammonia (NH3) from manures and the denitrification of NO3- and nitrite (NO2-) ions and their transformation into gaseous forms of N such as nitrous oxide (N2O) and nitric oxide (NO) can contribute to air quality and greenhouse warming impacts. Since N inputs are necessary for maintaining the viability of intensive agricultural systems, we must understand how management impacts the transformations, transport, and fate of N. The discussion of the transport and fate of N through agricultural systems must take into account the N cycle. Mitigation strategies that reduce the primary and secondary flows of N through the environment and that benefit farming and livestock operations must be developed.