Nitrogen compounds, soils

Ayanaba, A., Verstraete, W., and Alexander, M. Formation of dimethylnitrosamine, a carcinogen and mutagen, in soils treated with nitrogen compounds. Soil Sci Soc. Am. Proc., 37 565-568, 1973. 

Nitrogen fixation Conversion of atmospheric nitrogen into organic nitrogen compounds available to green plants a process that can be carried out only by certain strains of soil bacteria. 

One reason soils form is because of the endless migration of ions, molecules, and particles into the soil from meteoric inputs. Examples of meteoric inputs include H2O, CO2, O2, nitrogenous compounds, pollutants, salts, and dust. These molecules and compounds come from space, from the atmosphere and the oceans, and from other terrestrial systems. 

Loss of nitrogen compounds from soils is also a major pathway into the atmosphere for some compounds (e.g., N2O, NO, and NH3). As in the aquatic systems, parameters that play an important role in this process include the nature of the compound soil temperature, water content, pH, aeration of the soil and a concentration gradient of the gas in question. 

Plants consume nitrogen compounds present in the soil, and if growth is to continue, these compounds must be replenished, as by the addition of fertilizers. Until relatively recently, the fertilizer used for thi purpose consisted chiefly of animal wastes. Now chemists have learned to convert atmospheric nitrogen into fertilizer compounds by artificial methods. 

Figure 1.4 also shows two other reactions. In reaction 2, ammonia reacts with water to form ammonium hydroxide. Reaction 3 shows that ammonia can also be oxidized to form nitric acid from which all forms of nitrates can be produced. All three forms of nitrogen (ammonia, ammonium hydroxide, and nitrates in various forms) are commonly found in soil and can be added to soil to supply nitrogen to plants (see also Figure 6.5). This process thus opened up an inexpensive method of producing nitrogen compounds that would be used as fertilizers.

In other titrations, the component to be titrated is separated from soil and subsequently titrated. The simplest of these is the determination of soil ammonia. However, all forms of nitrogen in soil are important, so methods of converting other nitrogen-containing compounds to ammonia, distilling it, and determining its concentration by titration are important. 

Nitrogen in soil organic matter is mostly found in proteins and amino acids. Although the specific analysis for these important and interesting compounds... 

The titrimetric determination of soil constituents is most commonly applied to a limited number of soil analyses, namely, organic carbon, nitrogen compounds, carbonates, and chlorides. Determination of acid content by titration is generally not done because the titration curves are not amenable to typical titration analysis. Because of the color of soil and the fact that it is a suspension when stirred, it is often necessary to remove the constituent of interest before titration. In other cases, it is possible to do a direct titration using an appropriate indicator. However, even in these cases, detection of the end point is difficult. 

Si structure 251 smallpox 70 soil nitrogen compounds detected by 15N NMR, amides/peptides 126 amino adds 126 difficulties encountered with the method 126-127... 

Actinomycetes can metabolize a wide variety of organic substrates, including organic compounds that are generally not metabolized, such as phenols and steroids. They are also important in the metabolism of heterocyclic compounds such as complex nitrogen compounds and pyrimidines [42,49]. The breakdown products of their metabolites are frequently aromatic, and these metabolites are important in the formation of humic substances and soil humus [42,49]. 

GALBALLY, I.E. and ROY, C.R. (1983). The fate of nitrogen compounds in the atmosphere. In Freney, J.R. and Simpson, J.R. (eds). Gaseous Losses of Nitrogen from Plant-Soil Systems, 265-284. The Hague, Martinus Nijhoff/Dr Junk. 

Liao, Y.-Y., Wang, Z. T., Chen, J.-W.. Han. S.-K.. Wang. L. S.. Lu. G. Y.. and Zhao. T.-N. The prediction of soil sorption coefficients of heterocyclic nitrogen compounds by octanol/water partition coefficient, water solubility, and by molecular connectivity indices. Bull Environ. Contam. Toxicol, 56(5) 711-716. 1996. 

Many fertilizers are based on ammonia compounds. Modem agriculture requires more nitrogen in soils than is normally replaced by the nitrogen cycle, hghtning, decaying plants and animals, and other natural means... 

---