Urea

Urea

There has been a worldwide shift from prilling of Urea to granulation because the more desirable products made in granulator. This shift has taken place to supply growing fertilizer demand for larger, harder and denser particles, in spite of traditionally higher costs associated with granulation.

Urea finishing Processes

Urea can be prilled, granulated, flaked and crystallized. Presently only prilling and granulation is considered important. Most new plants that plan to ship internationally utilize granulation because of it’s far superior handling and storage qualities Comparative product characteristics are and a brief on two types of finishing process are given below:

Prilling

Using a spinning bucket, showerhead or acoustic vibration makes Prilled urea. The most common method is spinning bucket. Stamicarbon uses it’s own design for the buckets, Snamprogetti and Toyo both use the Tuttle bucket, that is also being used in our Kakinada plant.

In prilling, the urea melt is concentrated via vacuum evaporation to 99,8% and fed as quickly as possible into bucket to minimize buiret formation. The liquid form drops that then fall down a cylindrical concentrate tower that has either induced, forced or natural draft airflow. The prills solidify and are removed at bottom by belt conveying to storage. Some plants have a fluid-bed cooler in prill tower bottom and others use an in-line cooler before storage. If low biuret product is to be produced, the urea melt from the last decomposition stage of the synthesis plant is first crystallized and the crystals are then melted before prilling.

Granulation:

The granulation involves spring molten urea through series of the fine nozzles in a fluidized bed granulator. Cooling the liquid urea slowly while rolling it in layers, creating a harder more evenly sized granule makes granules of urea. There has been a world wide shift from prilling of urea to granulation because of the more desirable products made in granulators. This shift has taken place to supply growing fertilizer demand for larger, harder and denser particles, in spite of traditionally higher costs associated with granulation.

There have been many granulation processes developed and operated through the years. These include TVA pan granulation, C&I Girdler spherodizer spray drum, Norsk Hydro pan granulation and Fisons.

Rotary drum garnulators produce granules by spaying a concentrated melt (99.0 to 99.8%) onto small seed particles of urea in a long rotating cylindrical drum. As the seed particles rotate in the drum, successive layers of Urea are added to the particles, forming granules. Granules are removed from the granulator and screened. Off size granules are crushed and recycled to the granulator to supply additional seed particles or are dissolved and returned to solution process.

Pan ganulators operate on the same principle as drum granulators, except the solids are formed in a large, rotating circular pan. Pan granulators produce a solid product with physical characteristics similar to those of drum granules.

Since the solids are produced in a vide variety of sizes, they must be screened for consistently sized prills or granules. Cooled prills are screened and off size prills are dissolved and recycled to the solution concentration process.

Urea: Comparative Product Characteristics

Products Characteristics	Prilled (standard)	Granular (Bulk Blend)	Granular (Large Granule)*
Moisture (%)	0.3	0.2	0.25
Biuret (%)	0.9	0.7	0.70
Formaldehyde (Injection) %	0.3-0.4	0.45	0.45
Average size (mm)	1.7	2.5	up o 8.0
Crushing strength, kg	0.6(2mm)	3.0(2.5mm)	10(6.3mm)
Caking	Yes	No	No
Nitrogen content (%)	46	46	46
Color	Pure White	White	White

* Used, for example for forest application (3-5 mm size)

The properties in of different finished products of urea

Here some of the results of trials conducted on granular urea along with other urea products show the properties of various forms and their comparisons:

Experiment 1: Nitrogen losses and fertilizer N recovery from modified urea under wetland rice on a sandy loam soil in Mandya, Karnataka:

Source of N	Losses as applied N			Paddy Yield Kg/Hac
	Volatilization	Leaching	Total Loss
Prilled Urea	4.2	14	18.2	3780
NCU (Neem coated)	2.3	6.1	8.4	5040
Urea super Granular	2.1	6.8	8.9	5140

Experiment 2: Paddy yield comparison according to Urea type and granular urea sizes at MADA, Alor Setar, Malasiya, showed the following yields:

Urea Type/ size	Yield Kg /Ha
Prilled	4400
Granular (small) 2.1 mm	4946
Granular (Medium) 2.8 mm	4796
Granular (Large) 5.6mm	5067

Experiment 3: Point placement of Granular Urea:

Due to losses in leaching in Nitrogen as reported above case particularly paddy and other crops a new concept of use of Super Granule Urea (SGU) as point placement has been suggested. An experiment was conducted in BAU, Mymensingh- Bangladesh to study the yield patterns in different types of urea in a RBD (Randomized Block Design) in potato crop. The results were as below.

Type of Urea	Quantity of N*  Kg N/Hac	Potato Yield MT/Hac	Yield Kg /Ha
Control (without any Fertilizer)	0	10.44	NA
Urea prilled	109	17.52	NA
USG –2 from USG	73	18.40	5.02
USG-3 from USG	109	24.16	37.89

*Plant Nutrition Other than N was common for all treatments

Hence based on results of above experiments it is clear that:

• Higher the granular size of Urea lesser would be leaching losses and hence better yields.
• Volatilization losses in granular urea are almost half of Prilled as well as neem coated urea.
• Lesser quantity of granular urea gives better yields than granular urea due to saving in leaching and Volatilization losses.
• Point placement of granular urea gives much better yields to point placement, although prill urea also responds favorably to point placement.

Granulation mechanism:

Agglomeration Mechanism:

With most granular NPK Products (excluding the slurry based nitrophosphate-type processes), agglomeration is the principal mechanism responsible for the initial granule formation and subsequent growth. In most agglomeration-type NPK formulations, 50-75% of raw materials is fed as “dry” solids. These solid particles are assembled and joined into agglomerates (granules) by a combination of mechanical interlocking and cementing. The cementing medium for fertilizer granules are derived from salt solutions, for example, pre-neutralized ammonium phosphate slurry and or the dissolution of salts on moist surface of the soluble solid particles. The size, surface texture, strength and solubility of solid particles vary widely and have a profound influence on the granulation characteristics of the mixture.

Accretion Mechanism:

Accretion refers to the process in which Layer upon layer of a fluid material (material example, ammonium phosphate slurry) is applied to a solid particle causing it to grow in size. The slurry type accretion granulation processes are used to produce DAP, MAP,

TSP and some nitrophosphate compounds. The accretion process is quite different from the agglomeration process parameters for optimum operation of these slurry type accretion granulation processes is often quite different from those used in agglomeration processes. With a slurry type granulation applied, dried and hardened to a relatively firm substrate consisting of granules that are often product size or nearly product size. In this process, layer upon layer of new material is applied to a particle, giving the final granule a ‘onion-skin’ like stricture. In the process, of course, some agglomeration of particles also occurs, but this is not a predominant granule formation mechanism.

The recycle - to -product ratio for accretion type granulation is normally higher than that of the required for the agglomeration type processors. Accordingly, for a given production rate, the material handling capacity of the process equipment has been larger for the accretion type plants.

Soil Reaction of Urea (irrespective of type of Urea):

At the field, when the urea contacts the soil, a quick hydration and dissolution of granule is produced, and it disappears from the sight once dissolved. Then urea is subjected to the soil and climate’s own factors, and it breaks down until it reaches the proper form to be absorbed by the plants.

Plants take up nitrogen from soil in the mineral forms of nitrogen, both ammonium and nitrate before converting it to plant protein nitrogen. Plants vary in their preference to utilize either form of nitrogen. Nitrate is considered the main source because it is more mobile in the soil. On addition to soil, urea dissolves into soil solution and is converted to ammonium and then to nitrate.

Conversion is favoured by :

• Temperature: The activity range is wide. From -20° C to 37° C with optimum >20° C
• Organic Matter: Activity is enhanced in soil high in organic matter which favours microbial activity
• Time: The time for urea to be converted to ammonium will depend on the conditions of moisture and temperature. The reaction will begin to occur 24 hours after application and be complete within 2-5 days.

Recommendation

• Granulated Urea is as efficient as any other nitrogen fertilizer when incorporated into soil immediately after application.
• Urea often has a lower density than other fertilizers with which it is blended. This lack of “weight” produces shorter “distance of throw” when fertilizer is applied with spinner – type equipment. In extreme cases this will result in uneven crop growth and “wavy” or “streaky” fields
• In crops like paddy when it has to be used in standing water, as being larger size it takes a few minutes to drown in water. Hence, do not apply it even if there is slight movement of water. Though, it is always recommended to apply fertilizers when standing water level is only 2-3 cm.
• Do not store it near hay or organic products such as pesticides or fuels. Give room for air circulation and separate roof stowing by at least one meter.

Advantages in Use of Granulated Urea:

• Better industrial quality
• Even granulometry
• Harder granules
• Absorbs lesser moisture from atmosphere
• Can be mixed with other fertilizers
• Does not become compact
• Best adaptation to humid climates
• Less leaching loss hence, environment friendly
• It has less fines and dust when handled and transported
• It is three times harder than prilled urea.
• Granules are larger, harder and more resistant to moisture. As a result, granulated urea has become a more suitable material for fertilizer blends

Best Condition for efficient absorption of ammonium ions:

• When urea is well washed into soil.
• When the soil has high adsorption capacity
• When soil is sufficient moist
• When the soil a low pH
• At low temperatures

Unfavorable conditions of ammonium ions:

• Persistent drought
• High temperatures ( > 25° C) and strong winds
• Soil which has a low capacity for adsorbing ammonium ions
• Soil which has a high pH
• Dry cloddy soils that limit the physical mixing of urea with soil can increase volatilization.

Restriction:

• Do not mix with Superphosphates unless applied shortly after mixing. Urea will react with Superphosphates, releasing water and resulting water molecules and resulting in a damp material which is difficult to store and apply.
• Do not apply urea either forms of prilled or granular along with seeds or close to root zone resulting in death of seed /seedlings.

Critical Humidity:

Critical Humidity of urea at 30° C is 75.2%. (Critical humidity is level of humidity for a given temperature, at which a product begins to take up moisture from the atmosphere.

Solubility:

Urea (both granular and prilled) is completely soluble in water. Its maximum solubility is 30 kg of urea per 100 litres of water. Be aware that with water it gives a cold reaction, so take care on cold and frosty mornings.

Questions related to Fertilizer

1. Nitrogen in Urea is in form of:

Ans: Carbamide (Nitrogen After dissolution in soil it is converted to Ammonium ions)

2. Immediate after dissolution in soil urea is in what form?

Ans: Ammonium Ions

3. Most favorable temperature for conversion of Urea from Ammoniac form to Nitrate form

Ans: -20 to 370C

5. What is the Average size of prilled Urea?

Ans: 1.7 mm

6. What is Volatilization?

Ans: It is evaporation of Urea as ammonia into atmosphere when left exposed to sunlight and air.

7. What is Critical Humidity of Urea at 300C?

Ans: 75.20C (CH is the level of humidity for a given temperature at which a product begins to take up moisture from atmosphere.

8. What is maximum solubility of Urea in kg per 100 liters of water.

Ans: 30 kg in 100 liters of water.

9. What is a chemical formula of Urea? CO2(NH2)2/ CO(NH2)3/ CO(NH2)2 / CO(NH3)2

Ans: CO(NH2)2

10. Why plant is killed when Urea is applied to root zone Plant?

Ans: Due to toxicity caused by high pH and ammonia concentration around moist root zone

11. Urea should not be mixed with what fertilizer and why?

Ans: superphosphate due to release of water molecules and creating damp material.

12. Urea should not be stored with what fertilizer and why?

Ans: Ammonium Nitrate CRH Urea -75.2%, AN -59.4% but Urea +AN -18.1%

13. Percentage of Sulphur in ammonium Sulphate

Ans: S- 23%

14. Percentage of Nitrogen in Calcium Ammonium Nitrate & form of N

Ans: Ammoniacal N 12.5% & Nitrate N 12.5%

15. Chemical Formula for 21% zinc sulphate and called as

Ans: Zinc Sulphate Heptahydrate (ZNSO4. 7H2O)

16. Percentage of Boron in Borax

Ans: B-10.5%

17. Forms of Nitrogen & their percentage in 19:19:19

Ans: Nitrate 4.0% Anominiacal Nitrogen 4.5% & Urea Nitrogen 10.5%

18. Form of Nitrogen in Multi –K

Ans: Nitrate 13%

19. Weight of sample drawn from complex and straight fertilizers( other than micro nutrients) by Inspector

Ans: 400 gm

20. Who authorizes a Fertilizer Inspector to draw Fertilizer sample

Ans: A fertilizer Inspector is appointed by State or Central Government through notification.

Soya

SoyaNutrient Management

Nitrogen Nitrogen deficiency results in light thin and unhealthy plants. Bottom leaves of plant gets crincled like V shape and the tips and center if the leaf becomes yellow and it starts drying from the tip. New leaves of the plant also start showing these symptoms. These symptoms are more prominent in cold, drought, chemical matter and Nitrogen deficient conditions. Phosphorous In Phosphorous deficiency leaves from its tip and sides starts becoming blueish green, narrow light red purple. Tip of the leaves starts finishing. If plant starts getting Phosphorous then these symptoms are not shown in new leaves. Sometimes, these symptoms are seen in knee height crop or more taller crop. Potassium Bottom leaves of the plant starts yellowing from its tip and dries of or starts shedding. Plants gets stunted. These deficiencies mostly seen in wet, sandy, weathered soils. And in the soils in which, excess Potassium has been absorbed by the previous crops. Zinc In Maize grown areas Zinc deficiency is seen more. Zinc deficiency symptoms sometimes can be seen in germinating plants. White and Yellow spots are seen on the bottom side of the leaf. Whereas, middle portion and tip of the leaf remains green. New effective leaves of the plants are known as white buds. Zinc deficiency is more in the soils which have excess Phosphorous, high PH and more amount of chemicals. Boron Boron deficiency is not found commonly. Because of its deficiency irregular white patches and white line is seen on leaves. This is found in the soils which are dry, have high PH sandy, and have more chemicals. Yellowing of the leaves, drying and shedding of leaves can be because of poisonous nature of Boron. Magnesium Veins of bottom leaves of the plants turns yellowish white. Finally, old leaves ends and sides becomes red and purple and ultimately dies off. Its main causes are lower level of PH, sandy soils and excess of Potassium. Manganese In the soil Magnese deficiency is not seen oftenly. Veins of the leaves turns light yellow. Manganese deficiency often seen in the soils which has more amount of cow dung manure, chemical matters and high PH. It is also seen in sandy soils.

Cotton

Cotton

Nutrient Management

Introduction  Nitrogen  Phosphorus  Potassium  Micro Nutrients  Hybrid Cotton Nutrient Management Zonewise Nutrient Recommendations 

Introduction Soils in cotton growing areas have a low organic matter i.e., 0.5 to 1.25%, albeit cotton shed residues like burs, leaves, flowers etc., It responses to organic matter addition. In tropics and sub-tropics addition of 10-12 tones of farm yard manure annually is preferred. Application on seed lines is advantageous. The mineral nutrition of cotton depends on both the cotton roots ability to explore the soil and on the soils ability to supply N,P & K nutrients. The physico - chemical and biological conditions around the roots and their close interaction with organic matter in the soil & also play an important role in mineral nutrient uptake by plants. Nutrients play a role in the two major yield elaboration's process i.e., Growth, which involves quantitative modifications. With an increase in size and development or differentiate which involves quantitative modifications resulting in the acquisition of new morphological or functional properties. These processes are governed by various substances whose synthesis is indirectly linked to the supply of N, P & K to the plant. In tropical India, cultivar MCU-5 yielding 3.2 t/ha seed cotton removed 190 Kg N, 61 Kg P2O5 and 195 Kg K2O. The role of major, MicroNutrients and Nutrient deficiency as well excesses symptoms are as follows:

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Nitrogen Promotes the development of the green color in plants called chlorophyll and causes rapid, healthy growth. Too much nitrogen without enough of the other elements, however, can cause the plant to produce big stems and leaves and cut down on the production of cotton. It makes the plants weak and less able to resist attacks by insects and diseases or withstand wind and cold weather. Yield reduction was proportional to the length of the period during which the plant was subjected to N deficiency. Height of plant at 6 weeks and yield were positively correlated with NO3 content of leaf of 7 days old seedlings. Later stage-reduced supply of N is desirable for uniform maturation NO3 concentration. In petiole at beginning of flowering (1600 ppm), peak flowering (8000 ppm) end of flowering (2000 ppm)-fall below these levels reduce the yield. By application of N (under N deficiency) earliness of crop increases. N application (where N deficiency is observed) increased flowers three fold and bolls four folds. Combination of higher N level, frequent irrigation, high temperature results in excessive growth - fewer bolls than normal. Protein levels of seed increased. Reduced oil % but increased oil yield per unit area. Slightly longer fibers. Deficiency symptoms  Leaves turn yellowish green and eventually dry up and fall off. Cotton plants begin to look sick. Cotton can stand a lot more dry weather if they have a good supply of nitrogen. Limits the development of vegetative branches. N deficiency reduces the number of fruiting branches reduction in number of flowers. Reduce amount of fruiting. Number of seeds/boll increased Slightly decreased the lint seed ratio Excess nitrogen causes High pest, disease incidence. Lodging on excess N application. Lodging leads to regrowth increased boll rot.

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Phosphorus Phosphorus is found in every part of the plant. Its most important use is in cell division, which is the basis of growth. Essential for growth of the aerial parts of the plant For better root development It is also important in the development of the seed and lint and hastens maturity For protein synthesis Increase earlyness of crop (under deficient conditions if P is applied) Increased the No of early flowers by 30-40%. More matured bolls at the first picking (50%) Cotton requires less phosphorus than either nitrogen or potassium to produce its stalk and fruit. Deficiency Symptoms  Stunted growth may be the only evidence of a deficiency and can easily be overlooked or erroneously attributed to other factors. In the presence of adequate N, the leaves of some P deficient plants may become dark green or bluish green and show tints of bronze or purple along the margins. Seedlings grow slowly and maturity is delayed. A deficiency of P in plants usually does not produce striking visual symptoms. Phosphorus deficiency is often hard to spot in the field, unless the plants are alongside others that have received enough phosphorus. This is one reason for having a soil test made as a basis for deciding how much fertilizer to use. Although a soil may contain plenty of phosphorus, it can all be tied up in unavailable forms so that the plants are actually starved for phosphorus. Excess Phosphorus causes Excess phosphorous leads to more growth in lateral roots and fibrous rootlets Leads to trace element deficiencies particularly Iron and Zinc

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Potassium Too much nitrogen may cause the plant to grow too fast and form too much vegetation. Potassium helps in preventing this. Develops toughness in the plant - ability to resist diseases and insects and to withstand cold, wind and other adverse weather conditions. Deficiency Symptoms  Potassium deficiency is known as cotton rust. First, the leaves turn yellowish green brown necrotic spots appear between veins. Yellow spots appear between the veins and eventually turn black. The edges of the leaves die and become black. Finally, the whole leaf dies and falls off. In very bad cases the whole field may shed all its leaves. Without leaves the manufacture of plant food is stopped and bolls open before they are mature. This cuts down on the yield and produces weaker and shorter fibers.

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Micro Nutrients Magnesium Helps to keep in balance the growth of the plant. Necessary for the development of the cell walls and strength in the plant. Calcium deficiency causes plants to have weak stems and to topple over, somewhat like an attack of seedling diseases, deficiency symptoms are hard to spot in the field. Magnesium  This is one of the most important elements in the manufacture of chlorophyll. It also helps to move starch and phosphorus about in the plants. Magnesium shortage causes cotton leaves to turn purplish red, except that their veins remain green. The bottom leaves are affected first and drop off later in the growing season. Sulphur Sulphur also assists in the synthesis of chlorophyl and in making protein. Sulphur and nitrogen deficiencies look something alike. If yellowing symptoms shown up and you thing your nitrogen supply is adequate, chances are there for the plant for lacking Sulphur. Iron Iron is often present in the soil, but generally in an unavailable form. It is used in making chlorophyll and when lacking causes chlorosis of the leaves. Boron  Cotton requires boron in relatively large amounts as compared with other plants. This element and calcium do some of the same jobs. Scientists say that it is very important to maintain the right proportion of boron and calcium in the soil. A plant deficient in boron will be dwarfed, buds will die and the young leaves will turn yellowish green. In extreme cases boron deficiency causes squares to shed. Alkaline soils are most likely to be lacking in available boron. Manganese Evidently manganese plays a big part in some of the complex nutrient processes that are necessary for plant growth. Manganese deficiency cause leaves to turn reddish grey, except that the veins remain green. Too much available manganese will cause a disease known as crinkle leaf. Zinc  The production of chlorophyll is aided by zinc. When it is lacking, the plant will develop a chlorotic or mottle-leaf condition. Alkaline soils are more likely to be lacking in available zinc. Copper Apparently this element is needed only to a limited extent in cotton to help balance plant growth. Alkaline soils are likely to be lacking in available copper. Molybdenum  This is a newcomer to the list of necessary trace elements. Scientists do not know much about it, except that when it is lacking, plants tend to turn pale. It seems to be necessary for nitrogen utilization.

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Hybrid Cotton Nutrient Management The fertilizer management of hybrid cotton enjoys a spectacular difference from that of varieties. The cotton varieties have generally poor vegetative and reproductive growth than the hybrids. The hybrids have the potentiality to bear a higher leaf area per plant much earlier to varieties and require relatively higher nutrition at early stages. Similarly, the hybrid cotton plant bears more fruiting points and has larger bolls. This also necessiates more nutrition. As the nutritional demands at various stages of growth of hybrid cotton can ultimately decide the kappas yields, a careful planning of schedule and quantity of fertilizers is needed in case of hybrid cotton. Nitrogen The hybrid cotton is reported to response upto 320 kg N/ha. But a reduction in Kappas yield, if the level of added nitrogen was increased to 300 kg N/ha. A study of growth pattern of hybrid cotton plant indicates that: A faster rise in the rate of dry matter production leads to higher total dry matter production and accumulation at early stages. Higher leaf area per plant and longer leaf area duration recorded in hybrids at early stages of growth facilitate longer and higher absorption of added nutrients. Overlapping rhythms of leaf, branch, square, flower and boll development necessiates the supply of nutrients at various stages of growth rather than single dose. Several other workers have reported about the benefits of split application of nitrogen to hybrid cotton in increasing the Kappa's yields. Low temperatures reduce the availability of nitrogen to leaves. Severe shortage of nitrogen supply to the leaves causes reddening of leaves and reduce the Kappas yield drastically. Foliar application of nitrogen at flowering and post flowering period is found to be beneficial to increase the Kappas yield. The common recommendation and practice of Nitrogen through foliar feeding is 10-15 kg/ha. Phosphorous Efficiency of nitrogen utilization increases when applied in combination with phosphorous. Generally recommended applying phosphorous as basal dose, particularly in band or spot application to avoid more contact with soil particles. Potassium Application of Potassium increases the fibre maturity, micronaire value and fiber uniformity. Reduces wilt infection. Adequate and timely application of potassium forms good fertilizer management in hybrid cotton. Hybrid cotton has the potentiality to take up as much as 122-125 kg/ha but varies widely in different situations

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Zonewise Nutrient Recommendations Region & Season Varieties/ Hybrid Total -N (Kg/ha) Split applications P2O5 K2O Split application At days (K)       30DAS 60DAS 90DAS Entire Basal 30DAS 60DAS 90DAS Coastal Kharif Varieties 90 30 30 30 45 45 15 15 15   Hybrids 120 40 40 40 60 60 20 20 20 Rabi Varieties 135 45 45 45 45 45 15 15 15   Hybrids 150 50 50 50 60 60 20 20 20 Rayala Seema Mungari Varieties 20       20           American (Rainfed) 40 20 20   20           Hybrids 120 40 40 40 60 60 20 20     American (Irrigated) 90 30 30 30 45 45 15 15 15