Nitrogen Fertilizers

AMMONIUM NITRATE: Ammonium nitrate is a desirable, concentrated nitrogen fertilizer. It can be produced at a minimum cost for synthetic-nitrogen fertilizers. The principal problem in its use has been its great attraction for water. Since the beginning of World War II, methods have been devised to pellet and coat synthetic-ammonium nitrate, so that it does not cake or become wet with reasonable care in handling (Ross, et al., 1946). The cost is now about equivalent to that of ammonium sulfate on a nitrogen-content basis.

UREA: Urea is a concentrated synthetic-nitrogen fertilizer. When placed in the soil, the nitrogen hydrolyzes to ammonia. Urea is apparently absorbed quite readily through the leaves of many plants and is not as likely to cause leaf burn when sprayed on green foliage as are such in-organic compounds as ammonium sulfate and ammonium nitrate. Urea is marketed under such trade names as Nu-green, Uramon, and Agramon. Like ammonium nitrate, urea has a strong attraction for water and must be pelleted and coated to keep in a dry, granular condition.

UREA-FORM: Urea-form materials have been recently developed and proposed for use as fertilizers. A discussion of the preparation and properties of these materials is given by Clark, et al. (1948). These materials are produced by reactions between urea and formaldehyde. Chemical and biologic tests with urea-form products indicate that the rate at which the nitrogen present is converted to nitrate in soil increases with the urea: formaldehyde mol ration and with the solubility index (nitrogen going into solution by shaking 1 gram of materials in 400 ml. of water for 24 hours). The nitrification of certain of the less soluble products proceeds at nearly a constant rate for an extended period following an initial three to four weeks of low activity. In test with turf grasses, certain urea-form combinations produced a more uniform and sustained plant growth than standard sources of nitrogen. Furthermore, these materials stimulated greater root and crown development than conventional nitrogen sources (Armiger, et al., 1948).

CALCIUM CYANAMIDE: This product is produced by the reaction of calcium carbide and nitrogen gas at high temperatures. It is commonly called cyanamide. Cyanamide has a very alkaline reaction and is thus adapted to acid soils. Under acid soil conditions, it is gradually converted.

 FERTILIZER ELEMENTS AND FERTILIZER MATERIALS 

To cyanamide and urea. In alkaline conditions, some dicyanodiamide is formed which is quite stable and highly toxic to plants. In all areas where it is used, cyanamide is applied a few weeks in advance of planting to permit time for its nitrogen to become available and to avoid any toxic effects on growing crops.

AQUA AND ANHYDROUS AMMONIA: Aqua ammonia or ammonia liquor is used mostly in the fertilizer trade. Anhydrous ammonia gas is becoming popular for distribution with irrigation water. The gas is allowed to flow into the irrigation water and is carried into the land. Special machines have also been constructed for direct application into the soil as a side dressing. The popularity of this material is due largely to a lower cost than other nitrogen fertilizers and to the ease of distribution. Field distribution is often made by trained men working for fertilizer companies rather than by individual farmers.

 NITROGENOUS FERTLIZERS:

Sl.No.	Fertilizer	Formula	Total N%	%N in the from of			Equivalent
1	Ammonium Sulphate	(NH4)2SO4	20.5	NH4	NH4	NH4	Acidity	Acidity
2	Urea	O(NH2)2	44 to 46	NO3	NO3	NO3	Basicity	Basicity
3	Ammonium Nitrate	NH4 NO3	33 to 34	Amide	Amide	Amide	110	110
4	Ammonium Sulphate Nitrate	(NH4) SO4 NH4 NO3	26	20.5	20.5	20.5	-	-
5	Calcium Nitrate	Ca (No3)2	15.5	-	-	-	80	80
6	Calcium Ammonium Nitrate (CAN)	CaCO3 (35.5%) NH4 NO3 (59.0%) Mg Co3 (5.5%)	20.5 to 25	-	-	-	-	-
7	Ammonium chloride	NH4 CI	24 to 26	-	-	-	60	60
8	Sodium Nitrate	NH4NO3	16	-	-	-	-	-
9	Calcium Cynamide	CaCN2	21	44 to 46	44 to 46	44 to 46	85	85
10	Anhydrous Ammonia	NH3	82	17	17	17	-	-

INORGANIC NITROGEN: Inorganic soil nitrogen includes ammonium (NH4+), nitrite (NO2-), nitrate (NO3-), nitrous oxide (N2O), nitric oxide (NO), and elemental nitrogen (N2), which is inert except for its utilization by Rhizobia and other Nitrogen fixing microorganisms, for plants, NH4+), (NO2-), and (NO3-) are the most important and are produced from aerobic decomposition for soil on or from addition of nitrogen fertilizers. These forms represents 2 to 5% of total soil nitrogen (N2O-), and no are important nitrogen forms lost through denitrification.

Organic Nitrogen: Organic soil nitrogen occurs as proteins, amino acids, amins sugars, and other complex nitrogen compounds. the proportion of total soil nitrogen in these various fractions is : bound amino acids, 20 to 40%; amino sugars such as the hexosoning 5 to 10%; and purine and pyrimidine derivatives, 1% very little is known about the chemical nature of the 50% or so of the organic nitrogen not found in these fractions. proteins are commonly found in combination with clays, lignin, and other materials resistant decompostion the biological oxidation of free amino acids is an important source of (NH4+),  relative its other forms, the quantities of free amino acids in soils are low. 

 Properties of Nitrogenous Fertilizers:

• It contains 24% sulphur. Store well. It is applied at planting. nitrogen will be released slowly. Takes about a month for all NH4 to convert to NO3. The SO4 radical combines with Ca and forms CaSO4 radical combines with Ca and forms CaSO4 which is soluble and hence Ca is removed & soil becomes acidic.

• It is Hygroscopic. So fertilizer bag should not be kept open for long time, It is most suitable for foliar spraying (1 to 5%). It undergoes hydrolysis, converted to Ammonium carbonate. then to NH4 and NO3. It is also used as food in small quantities for animals. In India it is manufactured to a larger extent.

• Highly hygroscopic, highly explosive thus all begs are tightly sealed until ready to use. Keep all bags indoor in a dry place. Pile the stacks not higher than 6 bags.            It is not manufactured in India.

• When it is allowed to be in stores it seeks into hard cake which requires to be broken up.

• It is more hygroscopic than Urea and ammonium nitrate. It is not suitable for paddy. It is not manufactured in India.

• Stable salt, stores well

• Toxic to plants before it is converted into available form. Non leach able. It is a synthetic organic fertilizer. 

USES OF NITROGENOUS FERTILIZERS: Commercial nitrogen fertilizers should be used to supplement and balance the available nitrogen supply in soil. They are expensive unless a good crop response is obtained. If applied in excessive amounts, nitrogen fertilizers may lower crop quality much more quickly than large applications of the other fertilizer elements. The principal points in field use of nitrogen fertilizers are.

• Selecting the type of fertilizer for each particular situation,
• Determining the correct amount to apply,
• Applying the fertilizer at the proper time,
• Applying the fertilizer in the correct position for best crop utilization.

On arid soils where irrigation is practiced, there are certain general conditions under which nitrogen fertilizers can be used to advantage. Some of these are.

• When the soils are well supplied with phosphorus and other essential elements and nitrogen is the limiting element,

• When alfalfa or other deep-rooted legumes have not been grown in the rotation for several years or when a green manure has not been used,
• When farm manure is scarce and has not been used,
• When the soil is very sandy or gravelly in texture and/or light in color.