The Chemistry of Nitrogen in Soils

While a considerable amount of research has been done on soil N over the years, most of this work has been limited to qualitative and quantitative determinations of proteinaceous materials, amino adds, and ammonia. This leaves about one-third to one-half of the soil N unidentified and poorly understood, so that there is a need for more research and information in this area. 

The objective of this paper is to present an up-to-date account of what we know about the chemistry of soil N. The first part of this paper will deal with the distribution in different soils of proteinaceous materials, amino sugars, and ammonia, while the second part will focus on recent data on the identities and roles of heterocyclic N compounds, which also appear to play a significant role in supplying N to plant roots and microbes. 

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Another simple cation occurring commonly in soil is ammonium (NFLC). Because of the unique role and chemistry of nitrogen and nitrogen species in soil, it is discussed separately in Section 6.3 [5,6],... 

Maybe this solution is not final. The nitrogen bacteria teach [us] that nature in the refined forms of the chemistry of life still knows and realizes possibilities, the imitation of which is at present beyond our ability. It suffices that in the meantime, a new abundance of food benefits mankind from a richer nitrogen fertilization of the soil, and that the chemical industry is coming to the aid of the farmer who changes stones into bread on this peaceful earth ... 

Dolan, E. Zhang, Y. Klarup, D. The Distribution Coefficient of Atrazine with Illinois Soils ALaboratory Exercise in Environmental Chemistry, /. Chem. Educ. 1998, 75, 1609-1610. Driscoll, J. A. Acid Rain Demonstration The Formation of Nitrogen Oxides as By-Products of High Temperature Flame in Connection with Internal Combustion Engines, /. Chem. Educ. 1997, 74, 1424-1425. 

Globally, the oxides of nitrogen, NO (nitric oxide), NO2 (nitrogen oxide), and N2O (nitrous oxide), are key species involved in the chemistry of the troposphere and stratosphere. NO and N2O are produced mostly by microbial soil activity, whereas biomass burning is also an important source of NO. Nitric oxide is a species involved in the photochemical production of ozone in the troposphere, is involved in the chemical produaion of nitric acid, and is an important component of acid precipitation. Nitrous oxide plays a key role in stratospheric ozone depletion and is an important greenhouse gas, with a global warming potential more than 200 times that of CO2. 

Nitrogen fixation, denitrification, soil weathering, phosphate fixation, clay mineral degradation, and potassium and transition metal fixation are problems for which the reaction rates are usually as, or more, important than equilibrium. Most soil chemical applications of kinetics have been in soil microbiology and soil biochemistry, where the lack of equilibrium is more obvious. The use of kinetics in inorganic soil chemistry will undoubtedly broaden in the future. It can even be argued that kinetics is basic to thermodynamics, because equilibrium is the condition where opposing reaction rates are equal. 

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