Nitrogen Transformations in Soils, Agricultural Plants and the Atmosphere

Abstract

In dynamically developing countries plant production is on the increase together with the use of fertilizers and increasing air pollution with ammonia and nitrogen oxides (NOx) and nitrous oxide (N2O) is observed. When these forms of nitrogen occur at very high concentrations, they may be harmful to the environment (e.g. to cause the acidification of soils, an eutrophication, global warming, toxicity to plants, animals and for people). The monitoring of the concentrations of gases released into the atmosphere is important in order to reduce their amounts. However, this does not depend only on a human activity, but also on the intensity of the processes occurring in nature. Hence, in this paper the following issues are discussed: (1) the processes associated with the nitrogen cycle, occurring in soils, plants and the atmosphere, (2) the factors affecting them, (3) methods of the analysis of concentrations of these gases in the atmosphere and ammonium, nitrate, nitrite, organic and total nitrogen – in plants and soils. Both old, but commonly used methods and modern ones were presented, requiring specialized and expensive equipment. Alternative methods are suggested that are less expensive and more convenient in field studies, as well as enabling the monitoring of environmental pollution in the long term and at many locations simultaneously. The possibility of using a new method for the determination of trace amounts of ammonia in the air and ammonium nitrogen in plants and soils is pointed out. The review presents the most important factors affecting variable gas concentrations in the atmosphere, which, in addition to the use of fertilizers, may also include crop species, animal husbandry and meteorological conditions. Three spectrophotometric methods, the Nessler method, the indophenol method and the ISO 7150 method are compared to show that the ISO method is the best to analyse N concentrations in soils and plants. Passive samplers are used to measure ammonia in the atmosphere.