Managing denitrification in human-dominated landscapes

Abstract

Increases in food supply and fossil fuel consumption are among the hallmarks of the 20th century. These changes share a common characteristic – they both contribute to an excess supply of plant-available (i.e., reactive) nitrogen – with negative consequences to ecosystems and water supplies across the globe. While there are vast quantities of di-nitrogen gas (N₂) in the atmosphere, this form of N is unavailable (termed unreactive N) to the vast majority of biological life (Galloway et al., 2003). Globally, this unreactive N can be converted to reactive N by four major processes: N-fixing microorganisms (often in symbiotic association with plants, 140 TgNyear⁻¹), industrial fertilizer production (125 TgNyear⁻¹), fossil fuel combustion (25 TgNyear⁻¹), and lightning (5 TgNyear⁻¹) (Schlesinger, 2009). The benefits of increased food production by use of N inputs are clear. World economies also continue to rely on fossil fuels for transport and fertilizer production. As with many biogeochemical processes that are manipulated at global scales, increased N inputs has adverse and unintended consequences (Galloway et al., 2008).