A chronology of human understanding of the nitrogen cycle

Abstract

Nitrogen over the ages! It was discovered in the eighteenth century. The following century, its importance in agriculture was documented and the basic components of its cycle were elucidated. In the twentieth century, a process to provide an inexhaustible supply of reactive N (N r ; all N species except N 2 ) for agricultural, industrial and military uses was invented. This discovery and the extensive burning of fossil fuels meant that by the beginning of the twenty-first century, anthropogenic sources of newly created N r were two to three times that of natural terrestrial sources. This caused a fundamental change in the nitrogen cycle; for the first time, there was the potential for enough food to sustain growing populations and changing dietary patterns. However, most N r created by humans is lost to the environment, resulting in a cascade of negative earth systems impacts—including enhanced acid rain, smog, eutrophication, greenhouse effect and stratospheric ozone depletion, with associated impacts on human and ecosystem health. The impacts continue and will be magnified, as N r is lost to the environment at an even greater rate. Thus, the challenge for the current century is how to optimize the uses of N while minimizing the negative impacts.

Nitrogen deposition decreases the benefits of symbiosis in a native legume

“…In the legume-rhizobium symbiosis, rhizobia form nodules on the roots of legume hosts and fix dinitrogen (N 2 ) into ammonium (NH 4 + ) and other chemically active forms of nitrogen (N r ; i.e., all N species other than N 2 ; (Galloway et al 2013)). Prior to industrialization, biological nitrogen fixation (BNF) from this symbiosis dominated natural inputs of nitrogen into terrestrial ecosystems (Cleveland et al 1999).…”

Investigating the Combined Effect of Tillage, Nitrogen Fertilization and Cover Crops on Nitrogen Use Efficiency in Winter Wheat

“…It has been estimated that only half of the applied N inputs are recovered in harvested crops and their residues [5]. The N remaining in the soil can be lost by runoff, erosion, leaching or gaseous loss through denitrification and volatilization [6], which can have a detrimental impact on the environment [7,8].…”

Electrochemical Synthesis of Ammonia: A Low Pressure, Low Temperature Approach

“…Carl Bosch transformed this benchscale demonstration into an unprecedented industrial process as an engineer at BASF, resulting in commercial production in 1913. 5 Ultimately known as the Haber-Bosch process, it rose to be the most economical way to manufacture fertilizer, and remains so today. This process earned both men a Nobel Prize and enabled exponential world population growth, shown in Fig.…”