Nitrogen related Point Wise Notes For Competitive exam

NITROGEN

• Nitrogen constitutes about 78% of the atmospheric gases.

• Most of the N in soil is in organic form (95 to 99%).

• Total N in Indian soils vary from 0.02 to 0.1%.

• Value of total N in hill soils vary from 0.01 to 0.319%.

• Only about 1.5 to 3.5% of the organic N of soil mineralizes annually.

• Soils in India except those in the hills are generally low in organic matter and total N due to high temperatures.

• In mineralization process, organic N in soil organic matter is converted into plant-usable inorganic forms (ammonium and nitrate).

• Inorganic forms of N in soil include ammonium, nitrate, exchangeable ammonium and fixed ammonium.

• In well-aerated soils nitrate-N is the dominant form.

• Under anaerobic conditions ammonium is the dominant form.

• Nitrogen is taken up by crop plants as nitrate (NO3-) or ammonium (NH4+) ions.

• Most crop plants will equally take nitrate and ammonium.

• Rice is reported to prefer ammonium than nitrates.

• In rice ammonical and amide fertilizers are applied.

• Wheat prefer more ammonium at early growth stages and nitrate at later growth stages.

• Nitrogen interacts positively with all plant nutrients.

• Haber and Bosch first synthesized ammonia from N and H.

• Ammonia synthesis by Haber-Bosch process is carried out at a temperature of 1000 °C to 1200°C and at 200 to 100 atmospheres pressure.

• Industrial fixation (fertilizer nitrogen) by Haber-Bosch process is estimated at about 150 million tonnes per year by 2015.

• Global estimates of biological nitrogen fixation (BNF) are at 175 million tonnes per year.

• Anhydrous (without water) ammonia contains 82% N.

• Ammonia is the most reduced form of reactive nitrogen and most abundant alkaline constituent in the atmosphere.

• Urea was the first organic compound to be synthesized from inorganic materials.

• Urea was first separated from urine by Roulle in 1773, hence the name urea.

• In India, the first urea plant was set up in 1959 at Sindri in Bihar.

• About 80% of fertilizer N is consumed as urea.

• Nitrogen content in urea super granules is 46%.

• Urea is used as a substitute for protein in animal feed.

• The permissible limit of biuret in urea is 1.5% as per Fertilizer Control Order.

• Highest permissible concentration of urea in the spray solution for foliar spray is 3% beyond which the leaves get scorched.

• Plant leaves turn yellow due to N deficiency, because N is an important component of chlorophyll.

• Cereals remove 20-27 kg N, 8-18 kg P2O5 and 20-40 kg K2O per tonne of grain harvested.

• For producing each tonne (1000 kg) of wheat, the crop removes 25 kg N/ha.

• Nitrogen content in rice grains is lesser than wheat grains.

• The first nitrogen fertilizer used was sodium nitrate containing 16% N.

• Sodium nitrate also known as nitrate of soda or Chilean nitrate is considered as the first natural mineral containing fixed N and the only natural source of nitrate N.

• Ammonium nitrate contains 32 to 37.5 % N.

• Ammonium nitrate is hygroscopic.

• In calcareous soils, losses from ammonium nitrate are much less than from ammonium sulphate and urea.

• Ammonium sulphate contains 20.5% N.

• Organic N content of soil increases steadily with the application of ammonium sulphate.

• Ammonium sulphate nitrate contains 26% N.

• Ammonium sulphate nitrate is an acid forming fertilizer.

• Ammonium chloride (NH4Cl) contains about 26% N and is equally effective as ammonium sulphate for rice.

• Potassium nitrate contains 13.8% N and 36.5 % K.

• Calcium nitrate contains 15.5 % N and 19.5 % Ca.

• Calcium ammonium nitrate (CAN) is produced by mixing Ammonium nitrate and calcium carbonate.

• CAN is produced in two grades containing 20.5% N and 25% N.

• In CAN half of the nitrogen is in nitrate form and half of the nitrogen is in ammoniacal form.

• CAN is a neutral fertilizer.

• For alkaline soils, acid forming fertilizers and calcium containing fertilizers are preferred.

• During mineralization, ammonium is converted into nitrate by Nitrosomonas bacteria.

• In rice, percolation losses are 60 to 70 per cent of total water requirement.

• Nitrogen fertilizers are highly soluble in water, therefore subjected to leaching.

• Nitrates are subjected to leaching and nitrification losses in submerged soils.

• Leaching of N in the form of NO3- beyond soil profile is one of the major loss mechanisms that can be as high as 80% depending on the soil properties and water and nutrient-management practices.

• To reduce leaching losses solubility of nitrogen fertilizers is reduced.

• Inherently less soluble nitrogen fertilizers are Isobutylidene diurea (IBDU) – 32.2% N, Crotonilidene diurea – 32.5% N.

• Sulphur coated urea, shellac coated urea, neem coated urea are barrier coated nitrogen fertilizers.

• Borax, gypsum and nimin coatings reduce the rate of N release from prilled urea in lowland rice. Borax is effective and increases the productivity of rice.

• A major portion of N fertilizer applied to soil is lost through volatilization as gaseous ammonia.

• Loss of N due to ammonia volatilization from agricultural field in India is estimated at 4.1 million tonnes.

• Denitrification is sequential reduction of NO3- to N2 by denitrifying bacteria under anaerobic conditions.

• Loss of N due to denitrification from agricultural field in India is estimated at 3.1 million tonnes.

• On an average, denitrification losses reported in India ranged from 10 to 30 and 5 to 10 kg N/ha in rice and wheat respectively.

• Denitrification is controlled by soil moisture, redox potential (Eh), temperature, pH and substrate (NO3, NO2, NO and N2O) concentrations.

• N losses due to denitrification are likely to be most under alternate flooding and drying as obtained under aerobic rice systems.

• Agriculture sector contributes more than 80% of total anthropogenic NH3 emission to the atmosphere.

• Application of N fertilizer in soil contributes more than 25% of the total NH3 emission from agriculture.

• Current crop removal of N in India is estimated at 9.8 million tonnes.

• Apparent recovery of fertilizer N applied to rice in India is 30-40%.

• Recovery efficiency of fertilizer N in crop production is about 30-60%.

• Deep placement of fertilizer N increases its use efficiency.

• Nitrification inhibitors are chemicals that inhibit or retard oxidation of ammonium to nitrate N.

• Nitrapyrin, AM and DCD are the most widely used nitrification inhibitors.

• Growing of crops especially maize increases the release of inorganic N – forms.

• Loss of nitrate nitrogen from the soil is less in the presence of maize.

• Urease inhibitors reduce the rate of hydrolysis of urea to ammonium and can reduce loss of N due to ammonia volatilization when urea is surface applied.

• Examples of urease inhibitors are phenyl phosphorodiamidate (PPDA), amino thiosulphate, hydroquinone, phosphoric triamide, cyclohexyl phosphoric triamide, thiophosphoryl triamide, N-(n-butyl) thiophosphoric triamide.

• Adoption of best management practices improves nitrogen use efficiency.