eChapters

The main action of this drug is on the outlets of the body where the mucous membrane and the skin meet; these pain as from splinters. Marked improvement of symptoms while riding in a carriage. Acts best on the dark complexioned and past middle life. Syphilis after abuse of mercury. Pains appear and disappear rapidly. All discharges very offensive especially urine, faeces, and perspiration. Persons who have chronic diseases and take cold easily and disposed to diarrhoea. Excessive physical irritability.

The human body has many outlets where the mucous membranes and the skin meet. Any pain on account of problems in these regions is severe. It is a sticking pain. It is a pain as if somebody is piercing the surface with splinters. Nitric Acid is the remedy for problems of this type.

The skin and the mucous membrane join at the corners of the mouth, in the nose and at the anus. On the lips the corners crack, get ulcerated and swollen. In the mouth there are blisters with a lot of pus and swelling. The gums are swollen, ulcerated and spongy. Fissures occur in the canthi. Nitric Acid is the first remedy in such cases.

At the point where ammonium is produced, the reactions involved in organic nitrogen mineralization come to a halt. This most reduced form of inorganic nitrogen is the starting point for the nitrification process, which involves the biological synthesis of nitrate or nitrite from reduced nitrogen molecules. The ability of nitrifying bacteria to create nitrate, which is the primary nitrogen source ingested by higher plants, determines their relevance. Nitrate is formed in a variety of places, including soil, marine environments, manure piles, and sewage treatment, where it is the result of the final stage of turning organic nitrogen inoffensive.

The most oxidizable form of nitrogen is nitrate nitrogen (NO3 -N), which is found in minimal amounts in surface waters but can reach considerable concentrations in some aquifers. An essential plant nutrient, nitrate also contributes to eutrophication in receiving water bodies.
Principle
Nitrate reacts with phenol disulphonic acid and produces a nitro-derivative which in alkaline solution develops yellow colour due to rearrangement of its structure. The yellow colour follows Beer’s law and is proportional to the concentration of nitrate present in the sample. Ultraviolet (UV) technique measures the absorbance of nitrate at 220 nm, which is suitable for screening uncontaminated water (low in organic matter). A second measurement made at 275 nm, may be used to correct the nitrate value (because 275 nm is not absorbed by nitrate, but absorbed by other matter). The nitrate calibration curve follows Beer’s law up to 11mg NO3 -N /L.
Reagents
1. Stock nitrate solution (1ml=100 µg NO3 -N): Dry potassium nitrate (KNO3) in an oven at 105 oC for 24 h. Take 360.9 mg potassium nitrate and dissolve in distilled water and dilute to 500 ml. Preserve it with adding 1 ml of chloroform in per 500 ml stock nitrate solution. This solution will stable for at least 6 months.
2. Intermediate nitrate solution (1 ml = 10µg NO3 -N): Take 100 ml of stock nitrate solution and dilute it to 1000 ml of distilled water. This solution can be preserve by adding 2 ml of chloroform per 1000 ml. This Intermediate nitrate solution will stable for at least 6 months.
3. Hydrochloric acid (HCL) solution, 1N: Take 83 ml of hydrochloric acid and dilute it to 1000 ml of distilled water

Nitrite (NO2-) is formed in waters by oxidation of ammonia compounds (by aerobic nitrifying bacteria, e.g. Nitrosomonas) or by reduction of nitrate (by facultative anaerobic denitrifying bacteria, e.g. Pseudomonas). Such oxidation and reduction may occur in wastewater treatment plants, water distribution system, and natural waters. As an intermediate stage in nitrogen cycle, it is unstable. Very high nitrite levels are usually associated with waters having unsatisfactory microbiological activity.
Principle (Colorimetric method)
When nitrite (NO2 -) as nitrous acid (HNO2) mixes with sulfanilamide in an acidic environment (pH 2-2.5), a diazonium salt is created. This salt then combines with N-(1-naphthyl)-ethylenediamine dihydrochloride (NED dihydrochloride) to make a vivid pinkish red azo-dye. The amount of nitrite in the sample directly correlates with the colour that is created. At 543 nm, the colour follows Beer’s law up to 180 µg/L with a 1 cm light path. By diluting a sample, a higher nitrite concentration can be determined. Sulfanilamide + HNO2 + HCl ? Diazonium salt + H2O.
Diazonium salt + NED-dihydrochloride ? Red colouredazo dye

Plants take up nitrogen from soil either in the form of nitrate or ammonia. Nitrate taken by plants is reduced by nitrate reductase and nitrite reductase enzymes. They catalyze step-wise reduction of nitrate to nitrite and nitrite to ammonia. Ammonia occupies the key position in nitrogen metabolism for the synthesis of organic nitrogen. Glutamic acid dehydrogenase, GOGAT and GS are important enzymes which are involved in the conversion of ammonia into glutamic acid, a primary amino acid. The ?-amino group of several amino acids is formed as a result of transamination reaction through transaminase/ aminotransferase enzymes. This process is of great significance in amino acid metabolism.

Principle

The nitrogen of protein and other compounds is transformed into ammonium sulphate by acid digestion with boiling sulphuric acid. the acid digest is cooled, dilute with water, and made strongly basic with sodium hydroxide. The released ammonia is distilled into a boric acid solution or standard sulphuric acid solution. When boric acid is used to collect ammonia then is the titrated with standard sulphuric acid or standard hydrochloric acid. When standard sulphuric acid is used to collect ammonia then it is titrated with standard sodium hydroxide solution.

12.1 Introduction-Nitrogen

Nitrogen is a chemical element which has the symbol N and atomic number 7. Elemental nitrogen is a colourless, odourless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78.1% by volume of Earth’s atmosphere. Nitrogen is a constituent element of all living tissues and amino acids. Many industrial important compounds, such as ammonia, nitric acid, and cyanides are made up of nitrogen.

12.1.1 History

Nitrogen (Latin nitrogenium, where nitrum (from Greek nitron) means “native soda”and genes means “forming”) is formally considered to have been discovered by Daniel Rutherford in 1772, who called it noxious air or fixed air. That there is a fraction of air that did not support combustion is well known to the late 18th century.

Argon was discovered when it is noticed that nitrogen from air is not identical to nitrogen from chemical reactions. Compounds of nitrogen were known in the Middle Ages. The alchemists knew nitric acid as aqua fortis (strong water). The mixture of nitric and hydrochloric acids is known as aqua regia (royal water), celebrated for its ability to dissolve gold (the king of metals). The earliest industrial and agricultural applications of nitrogen compounds involved uses in the form of saltpeter (sodium- or potassium nitrate), notably in gunpowder, and much later, as fertilizer, and later still, as a chemical feedstock.

Nitrogen is a nutrient and occurs in many forms including ammonia, organic, nitrate and nitriteeach of which may be tested for in a variety of ways. Under normal circumstances, the nitrite form of nitrogen will not be present in large quantities due to its rapid oxidation orconversion to nitrate. The presence of large concentrationsof ammonia in a stream or lake can create a large oxygen demand. This demand is caused by the conversion of ammonia to nitrate. High concentrations of nitrate in waste water treatment plant effluent can cause algae to grow in large quantities.

Current status

For many years, the protein contentof foods has been determined on the basis of total nitrogen content, while the Kjeldahl (or similar) method has beenalmost universally applied to determine nitrogen content (AOAC, 2000).Nitrogen content is then multiplied by a factor to arrive at protein content. This approach is based on two assumptions: thatdietary carbohydratesand fats do not contain nitrogen, and thatnearly allof the nitrogen in the dietis present as amino acids in proteins. On the basis of early determinations, the average nitrogen (N) content of proteins was found to be about 16 per cent, which led to use of the calculation Nx6.25(1/0.16 = 6.25) to convertnitrogen contentinto protein content.

Nitrogen assimilation is the formation of organic nitrogen compounds like amino acids from inorganic nitrogen compounds present in the environment. Organisms like plants, fungi and certain bacteria that cannot fix nitrogen gas (N₂) depend on the ability to assimilate nitrate or ammonia for their needs. Other organisms, like animals, depend entirely on organic nitrogen from their food.

Plants absorb nitrogen from the soil in the form of nitrate (NO₃ ^-) and ammonia (NH₄). In aerobic soils where nitrification can occur, nitrate is usually the predominant form of available nitrogen that is absorbed. However this need not always be the case as ammonia can predominate in grasslands and in flooded, anaerobic soils like rice paddies. Plant roots themselves can affect the abundance of various forms of nitrogen by changing the pH and secreting organic compounds or oxygen. This influences microbial activities like the interconversion of various nitrogen species, the release of ammonia from organic matter in the soil and the fixation of nitrogen by non-nodule-forming bacteria.

There are two mini-cycles in the soil nitrogen cycle:

1. Soil-based processes such as mineralization, ammonification, nitrification, and immobilisation include the conversion of organic nitrogenous molecules to plant-useable mineral forms, and subsequently back to biomass (microbial, plant and indirectly animal biomass).
2. The process of converting atmospheric nitrogen into forms available to the living components of the ecosystem, i.e. nitrogen fixation and the transformations within the soil, as well as the return of the fixed nitrogen to atmospheric inert forms of nitrogen through denitrification, are all soil and biosphere resident processes.

Soil microorganisms are the most important agents in the cycling or transformation of various elements (N, P, K, S, Fe etc.) in the biosphere; where the essential elements undergo cyclic alterations between the inorganic state as free elements in nature and the combined state in living organisms. Life on earth is dependent on the cycling of nutrient elements from their elemental states to inorganic compounds to organic compounds and back into their elemental states.

The microbes through the process of biochemical reactions convert / breakdown complex organic compounds into simple inorganic compounds and finally into their constituent elements. This process is known as “Mineralization”.

Mineralization of organic carbon, nitrogen, phosphorus, sulphur, and iron by soil microorganisms makes these elements available for reuse by plants. In the following paragraphs the cycling or transformations of some of the important elements are discussed.

To meet the food needs of the burgeoning population, India will need to produce 300 million tonnes of food grains by 2020. At present more than 75% of the total food grains produced in the country are of rice and wheat. Use of nitrogenous fertilizers has contributed much to the remarkable increase in production of rice and wheat in India that has occurred during the past three decades. During the last half-decade or so while fertilizer N consumption is touching new heights, the production of both rice and wheat is showing a trend of plateauing. In fact, fertilizer N efficiency of food grain production expressed as partial factor productivity of N (PFPN) has been decreasing exponentially since 1965. The PFPN is an aggregate efficiency index that includes contributions to crop yield derived from uptake of indigenous soil N. fertilizer N uptake efficiency, and the efficiency with which N acquired by the plant is converted to grain yield. A decrease in PFPN occurs as farmers move yields higher along a fixed N response function, unless other factors shift the response function up. In other words, an initial decline in PFPN is an expected consequence of the adoption of N fertilizers by farmers and not necessarily bad within a system’s context

Under agricultural conditions, the nitrogen removed is usually greater than the nitrogen input. To maintain fertility, nitrogen must be returned to the soil. This takes place mainly by biological nitrogen fixation, which is responsible for the major reduction of dinitrogen to ammonia that is used by the plants. Biological nitrogen fixation accounts for most of the fixation of atmospheric nitrogen in to Ammonium, thus representing the key entry point of molecular nitrogen into the biogeochemical cycle of nitrogen (Fig.4.1). Some bacteria can convert atmospheric nitrogen into ammonium. Most of this nitrogen fixing prokaryote is free living in the soil.

Nitrogen is the most important element on which depends growth and productivity of plants. It is also the most abundant molecule in the atmosphere (80%), yet it cannot be utilized by plants. The plant utilizable form of nitrogen is either, its most oxidized form, the nitrates or the most reduced state, the ammonia.  The indiscriminate use of nitrogenous fertilizers amounts to depletion of non-renewable fossil fuels used in fertilizer production. Sustainable agriculture depends largely on renewable resources and on-farm nitrogen contributions are achieved largely through biological nitrogen fixation (BNF), which helps in maintaining and/or improving soil fertility by using atmospheric nitrogen. Annually BNF is estimated to be around 175 million tonnes of which close to 79% is accounted for by terrestrial fixation.

Although the Dacron bag technique for protein degradation measurement is relatively simple and not too expensive as compared to in vivo measurements, the technique is not easily adaptable in laboratories that are not fully equipped to maintain cannulated animals. Therefore, different alternative approaches such as measurement of protein solubilities in buffer, enzymes and detergent solutions have been tried (Pichard and Van Soest, 1978; Krishnamoorthy et al., 1982, 1983, 1995; Aufrere et al.,1991; Prabhu et al., 1996; Licitra et al., 1996 and 1998). The advantages of these approaches are that, they are simple, rapid, economical and repeatable. However, since the enzymes used are not of rumen microbial origin, degradation obtained from these enzymes may not be a true .reflection of degradation occurring in the rumen. Nevertheless, because of their simplicity and rapidity, in situations where large number of samples are to be compared, in vitro techniques serve as useful tools.

Introduction

As per statement of Dr. Henneberg of Weende Experiment Station (Göttingen, Germany) the carbohydrates are divided into two groups; crude fiber and nitrogen free extract. The nitrogen free extract, which  comprises the sugars, starch and a large part of the material classed as hemicellulose, is determined by difference. It is represented by the figure obtained when the sum of the water, ash, protein, fat and crude fiber of a feed is subtracted from 100. Since the figure is determined by difference instead of directly, it includes the cumulative errors of the other determinations and thus is not an exact value.

14.1. Determination of Total Nitrogen in Soil (Modified Kjeldahl Method)

Nitrogen mostly present in soil in organic form. Relatively small amount of nitrogen usually occur in ammonium and nitrate form, the available form. The Kjeldahl method of total N determination includes both organic and ammonium form and with modification nitrate form of N can also be included.

21.1 Determination of Total Nitrogen in Soil (Modified Kjeldahl Method)

Nitrogen mostly present in soil in organic form. Relatively small amount of nitrogen usually occurs in ammonium and nitrate form, the available form. The Kjeldahl method of total N determination includes both organic and ammonium forms and with modification nitrate form of N can also be included.

Principle

When soil is digested with concentrated sulphuric acid organic nitrogen is converted to ammonium sulphate. To speed up the reaction a digestion mixture composed of sodium (or potassium) sulphate (to raise the boiling point of H₂SO₄) and cupric sulphate (CuSO₄) - selenium powder (catalyst) is used.

Abstract

Nitrogen is the most limiting nutrient controlling production of all agricultural systems. Application of N fertilizer has increased food production tremendously all over the world. However, it also contributes towards global warming and ozone layer depletion through emission of nitrous oxide, a greenhouse gas (GHG). Therefore, there is a need to assess the possibilities of N management for climate change abatement and food security enhancement, while minimizing environmental and human health impacts. In this chapter, role of gaseous-N emission on N use and various mitigation options for Indian agriculture have been discussed. For the base year 2007, the direct and indirect N₂O emissions from Indian agricultural soils was estimated to be 136.29 Gg (35.3 Tg CO₂ equivalent) and 30.61 Gg (5.8 Tg CO₂ equivalent), respectively.

Before the invention of N fertilizer, mineralization of organic N ( present in dead plants and animals or manure) was the main method used to obtain ammonium and nitrate nitrogen. Mineralization is conducted by soil microbes resulting in ammonium ion. Most Nitrogen is absorbed by plants in the form of Nitrate (NO-₃). Ammonium is converted to Nitrate with the help of  soil bacteria. Nitrogen is a very mobile element and is easily lost from the soil. Ammonium (NH₄+) can be converted to Ammonia (NH₃). The gaseous ammonia can be lost to the atmosphere.  Nitrate can be lost through denitrification. Nitrate nitrogen is reduced to nitrous oxide (N₂O), elemental nitrogen (N₂) and nitric oxide (NO). All are volatile. Denitrification occurs under conditions of high water availability and temperatures higher than 10^ºC.