NITROGEN CYCLE AND BIOLOGICAL PRODUCTION

Soil fertility and importance of nitrogen input
The inputs of nutritive substances to a soil have two fold character: to maintain and/or improve soil quality on one side and to nourish crop on the other side. The noted purpose can be provided by: green-dung (stubble ploughing) and manure, allowing organic matter to be decomposed biogenically in the soil. The present organic matter provides fertility, regulating water management and soil structure, at the same time. The origin and species of organic matter, green-dung or manure, determine their quality; the ploughed stubble contain mainly lingo-cellulose, poor in nitrogen, while the manure, dependently, again on origin and fermentation degree, include nitrogen, lesser (fresh with high straw share) or more (completely fermented).
Nitrogen level in agricultural soil is inadequate for both, the crop and present microorganisms, so it had to be added. The input of completely fermented manure satisfies the soil nitrogen quantity, despite its mineralization is continued, what prolong manure effect during three years (50% was consumed in first year of application and the rest was consumed during next two years). Additionally, the gradual input of mineral nitrogen, combined with manure, have to be done in agreement with degree of nitrogen output by crop. The presence of humus, acquired from organic matter decomposition, act upon water and minerals retaining, inhibits soil leaching, in a great level.
Unrestrained, overdose nitrogen input, without knowledge of present status inside of the soil, could lead to the crop overgrowing, it’s lodging and breaking. Unspent part of nitrogen fertilizer leaches to ground water, polluting water-flows. The observed facts underline importance of nitrogen for crops and soil fertility maintenance and possible risks of pollution, what bring ahead control of soil nitrogen content and its input, dictated by crop outputs. The control is going to be mandatory in Europe and in this purpose is developed N-min (mineral nitrogen) method, quick and cheap.

Nitrogen cycle in soil and pollution
The nitrogen is element absent in terrestrial minerals (the exceptions are a few phyllosilicates that contain ammonia substituted for potassium), but present in air as N2 molecule (gas). It has two outmost forms: NH4+1 and NO3-1, which are transformed by plants to a -NH2 form (amino group), all living systems’ essential. The living organisms incorporate nitrogen, although the non-living organic matter releases it. The both pathways substantially exist in soil. The soil nitrogen part, as segment of global nitrogen cycle represents potentially the most adjustable part and aught to be in equilibrium with carbon cycle, at disposal. The observed chain shouldn’t be disturbed, as well as, it could be easily made, in the course of nitrogen un-enclosing (soil depletion), leaching and microorganisms destroying (pesticide overdosing).
Nitrate and ammonium salts, regardless to their origin, tend to dissolve in the presence of even small amounts of liquid water in soil and afford to be leached. Mineralization of organic matter occurs sequentially, over gaseous intermediates giving nitrogen trace gas emissions. They are highly reactive; depending on oxidation degree, react with water and/or oxygen. The noted process is spontaneous. The upper observed nitrogen salts leaching and trace gas emissions could be regard as the pollution source of the first order (biological pollution), while the industrial waste could be regard as the pollution source of the second order (product of civilization).
At the soil under processing the two ways of nitrogen output occur: through emission of trace gases and organic forms (living systems). The intensity maintenance of noted nitrogen cycle could be provided by input of: organic residues, mineral fertilizers and presence of soil microorganisms. Meanwhile, the shifting of soil nitrogen and carbon cycles equilibrium (have to aspire to stoichiometric relation) result in deprivation of soil fertility. Then again, the restoring of soil fertility is truly distressing and mainly uncertain process.
Meanwhile, the nitrogen and carbon misplacing through volatile forms should be surpassed by production of huge amounts of oxygen via forest areas, as counterbalance to areas with intensive agricultural production. Additionally, in the aim of atmosphere protection from biological and industrial nitrogen and carbon dioxide emission, the equilibrium have to be restituted with spontaneous oxygen production by carbon capturing (photosynthesis).