ENVIS Centre, Ministry of Environment & Forest, Govt. of India

Printed Date: Wednesday, August 21, 2019

Nitrogen fertilizer

Nitrogen fertilizer
Millions of metric tons of reactive nitrogen entering the U.S. environment each year.
Source: Reactive Nitrogen in the United States
A long-term effect of all ammonium-based nitrogen fertilizers is to lower soil pH. Anhydrous ammonia, urea, diammonium phosphate, and nitrogen solutions, when first applied, greatly but temporarily increase soil pH in the zone of application.
Source: extension.psu.edu/agronomy-guide/cm/sec2/sec28
Sl.No. Fertilizer Formula Total N% %N in the from of Equivalent
1 Ammonium Sulphate 20.5 (NH4)2SO4 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 -- --
Source: http://agropedia.iitk.ac.in/content/properties-and-uses-organic-and-inorganic-nitrogen-fertilizers-crop-production
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.
Source: http://agropedia.iitk.ac.in/content/properties-and-uses-organic-and-inorganic-nitrogen-fertilizers-crop-production
Uses of nitrogenous fertilizers:
Source: http://imgaws.ehowcdn.com/350x235p/photos.demandstudios.com/getty/article/241/86/dv118039_XS.jpg
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.
Source: http://agropedia.iitk.ac.in/content/properties-and-uses-organic-and-inorganic-nitrogen-fertilizers-crop-production
Plant nitrogen-fixing cover crops: Certain plants, like legumes and clover, store nitrogen in nodules at their roots. These nodules release nitrogen into the soil gradually while the plant lives, and when the plant dies, the remaining nitrogen enhances the overall quality of the soil.
Source: http://eorganic.info/sites/eorganic.info/files/u118/4439_Legume_based_cropping_system_graphic.jpg
  • Just toss some legumes on the soil. Mung beans are suggested since they don't grow too big but they grow fast.
  • To replenish Nitrogen on the soil. Try fallowing. When resting your plot on the 7th year, sow some mung beans.
  • Don't harvest the mung beans, instead, let the seeds fall into the ground for more nitrogen-fixers. Do this, especially if you will be planting heavy feeders like corn on the next growing year.
Nitrogen transformations in the soil
Source: www.farms.com
Nitrogen undergoes transformations in the soil, depending on the chemical composition of the nitrogen applied. While nitrate is taken up directly by plants, ammonium and urea need to be first transformed into nitrate. Transformation losses are lowest with nitrate and highest with urea.
  • Application of fertilizers- containing mineral nitrogen as urea, ammonium, nitrate or a mix. Organic fertilizers and manure contain mostly complex organic nitrogen compounds and ammonium.
  • Uptake of nitrate is rapid due to the high particle mobility. Most plants therefore prefer nitrate over ammonium.
  • Uptake of ammonium is slower than nitrate. Ammonium is bound to clay particles in the soil and roots have to reach it. Most of the ammonium is therefore nitrified before it is taken-up by plants.
  • Nitrification by soil bacteria converts ammonium into nitrate in between a few days and a few weeks. Nitrous oxide and nitric oxide are lost to the atmosphere during the process.
  • Denitrification is favoured by lack of oxygen (water logging). Soil bacteria convert nitrate and nitrite into gaseous nitrous oxide, nitric oxide and nitrogen. These are lost to the atmosphere.
  • Immobilization transforms mineral nitrogen into soil organic matter. Activity of soil microbes is mainly stimulated by ammonium. Immobilized nitrogen it is not immediately available for plant uptake, but needs to be mineralized first. Mineralization of soil organic matter (and manure) releases ammonium into the soil.
  • Hydrolysis of Urea by soil enzymes converts urea into ammonium and CO2 gas. Depending on temperature, hydrolysis takes a day to a week. The soil pH around the urea granules strongly increases during the process, favouring ammonia volatilization.
  • Ammonia volatilization occurs when ammonium is converted to ammonia and lost to the atmosphere.A high soil pH levelfavoursconversionof ammonium to ammonia. If conversion takes place at the soil surface, losses are highest. These two conditions are met when urea is spread and not immediately incorporated.
  • Leaching of nitrate occurs mainly in winter when rainfall washes residual and mineralized nitrates below the root zone. Accurate fertilization prevents leaching during the growth period.
Source: http://yara.com/doc/33521_Nitrate_-_Pure_Nutrient.pdf
Nitrogen Cycle in the Soil
Source: https://www.youtube.com
Enhancing fertilizer efficiency
Nitrogen needs to be available in sufficient quantities so that it does not limit growth and yield. However, excess amounts of nitrogenbeyond short-term plant needs may be lost to the environment or result in luxury consumption. Matching nitrogen availability precisely to current plant needs and actual soil nutrient supply maximizes yield, minimizes environmental impact and optimizes profit.Split application is considered best agricultural practice under most Conditions. Fertilizers offering a predictable release of plant-available nitrogen are best suited for split application. This is the case for ammonium nitrate and calcium ammonium nitrate,but generally not for urea. Hydrolysis of urea and volatilization losses heavily depends on climatic conditions after spreading, especially on rainfall.
Source: http://www.slideshare.net/showkateytoo/nutrient-use-efficiency
They cannot be predicted reliably, resulting in either under- or oversupply of nitrogen. The Defra study has highlighted the unreliability of urea, finding volatilization losses that varied from nitrate. The results are shown in the charts below. Even with a spreading width of only 21 meters, a mild breeze of 4 m/s resulted in 26 % variation of application rate with urea, whereas it was only 6 % with CAN! A spreading inaccuracy of 26 % is typically associated to yield losses of 2 % for winter wheat. Larger spreading width results in even higher losses. Lower spreading width increases work load and reduces strike force. Reducing fertilizer input by sensor controlled spreading Precision farming tools can further enhance spreading accuracy. The Yara N-Sensor™ offers farmers real-time control over fertilizer application and GPS based accounting of nutrient supply. The plant nitrogen need is measured continuously during spreading. The Yara N-Sensor™, when being used for spreading homogeneous nitrate fertilizers, guarantees highest yield with lowest nitrogen input. More than a hundred field trials have compared the N-Sensor to common farming practice, demonstrating an increase in protein content by 0,2-1,2 %, an increase in yield by 7 % and a cut in nitrogen input by 12 %. Reducing soil acidification Nitrogen fertilizers can have an acidifying effect on certain soils, which needs to be corrected by liming. Applying fertilizers with high nitrogen efficiency reduces acidification and liming requirements. Fertilizers such as calcium ammonium nitrate contain limestone or dolomite, leading to further savings in cost 2 to 58 % of applied nitrogen! And time for lime application. Balanced nutrition is another prerequisite of economic fertilizer use. Insufficient supply of Phosphorus, Potassium or Sulphur can diminish nitrogen use efficiency. Frequent soil sampling provides data on actual supply of nutrients from the soil and fertilizer needs.
Source: 33521_Nitrate_-_Pure_Nutrient.pdf
Split application of ammonium nitrate with winter wheat. The actual fertilizer need depends on both, soil nitrogen supply and plant need. Tools such as Yara N-Tester or N-Sensor facilitate crop ammonium nitrate is significantly lower than that provides immediate information on actual monitoring and help to ajust split applications accurately.
Source: nitratesmartagriculturefinalversion-130709024004-phpapp02/95/smart-agricultureen
Eco-friendly liquid formulations for Nitrogen fertilizer protection
Nitrogen fertilizers suffer from volatilization above ground and nitrate leaching after application requiring innovative formulations based on urease and nitrification inhibitors to increase yield.
Benefits
Source: www.solvay.com
  • Eco-friendly solvent system to formulate solid inhibitors into liquid products
  • High efficiency formula
  • Low viscosity liquid product
  • Provides more nitrogen to the plant
  • High solubility in liquid nitrogen fertilizer
  • Safe solvents to answer multiple needs
Source: http://www.solvay.com/en/markets-and-products/featured-products/N-Protect.htm