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Title: NITROGEN FATE AND TRANSPORT IN AGRICULTURAL SYSTEMS

Author
item Follett, Ronald
item Delgado, Jorge

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2002
Publication Date: 7/1/2002
Citation: FOLLETT,R.F., DELGADO,J.A., NITROGEN FATE AND TRANSPORT IN AGRICULTURAL SYSTEMS, JOURNAL OF SOIL AND WATER CONSERVATION, 2002. 57:402-408.

Interpretive Summary: Nitrogen (N) is one of the most important nutrients and is central to the growth of all crop plants. But N also forms some of the most mobile compounds in the soil-plant-atmosphere system, and there is mounting concern about agriculture's role in N delivery into the environment. Nitrogen represents the mineral fertilizer most applied to agricultural land because available soil-N supplies are often inadequate for crop production. The fate and transport of N must be considered within the context of the N cycle. Fertilizing for crop N uptake near the point of maximum yield (Nmax) generally is an economically and environmentally acceptable practice because Nmax can serve as a reference point below which the optimum N rate is located depending upon the N/crop price ratio. The objective is to lower the rate and duration of the loss processes themselves. The goal is to decrease residual soil NO3- (RSN) and keep RSN in the soil-crop system by curtailing transport processes (leaching, runoff, erosion, and gaseous losses).

Technical 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.