Claims:We Claim:
1. A controlled release fertilizer composition comprising urea having 10% to 45% Nitrogen coated with a source of organic carbon and a lignosulfate compound.
2. The fertilizer composition as claimed in claim 1, wherein the source of organic carbon is a manure or soil conditioner.
3. The fertilizer composition as claimed in claim 1, wherein the lignosulfate compound is calcium lignosulfate, ammonium lignosulfate, sodium lignosulfate or a combination thereof.
4. The fertilizer composition as claimed in claim 1, wherein the coating optionally comprises nitrification and urease inhibitors selected from the group comprising 2 chloro-6 (trichloromethyl pyridine, 4 amino 1,2, 4 -6 triazole –HCl, 2,4 diamino -6-trichloro methyltriazine, Dicyandiamide (DCD), Cyanoguanidine (DMPP), ThioUrea, 1 mercapto-1, 2, 4 triazole, 2 amino -4 chloro 6 methyl pyramidine, 3, 4 dimethylpyrazole phosphate (DMPP), 1-amide 2 thiourea (ASU), Ammonium ThioSulphate (ATS), 1H-1, 2-4 Triazole (HPLC), 5-ethylene oxide -3-trichloro-methyl1,2,4 thiodiazole, 3- methylpyrazole (3-MP), 1-carbamoyle-3-methyl –pyrazole (CMP) and neem oil.
5. The fertilizer composition as claimed in claim 1, wherein the composition optionally comprises a filler selected from the group comprising bentonite, smectite, montmorillonite and other clays.
6. The fertilizer composition as claimed in claim 1, wherein the composition optionally comprises a hydrophobic compound selected from the group comprising urea aldehydes condensation product such as Urea Formaldehyde (UF) and chemically decomposing compounds such as isobutylidene –Diurea (IBDU).
7. The fertilizer composition as claimed in claim 1, wherein the composition optionally comprises micronutrients.
8. A method for preparing a controlled release fertilizer composition comprising mixing urea having 10 to 45% Nitrogen with a source of organic carbon and a lignosulfate compound and then drying the mixture.
9. The method for preparing a fertilizer composition as claimed in claim 8, wherein the source of organic carbon is a manure or soil conditioner.
10. The method for preparing the fertilizer composition as claimed in claim 8, wherein the lignosulfate compound is calcium lignosulfate, ammonium lignosulfate, sodium lignosulfate or a combination thereof.
11. The method for preparing the fertilizer composition as claimed in claim 8, wherein the mixture is optionally coated with nitrification and urease inhibitors selected from the group comprising 2 chloro-6 (trichloromethyl pyridine, 4 amino 1,2, 4 -6 triazole –HCl, 2,4 diamino -6-trichloro methyltriazine, Dicyandiamide (DCD), Cyanoguanidine (DMPP), ThioUrea, 1 mercapto-1, 2, 4 triazole, 2 amino -4 chloro 6 methyl pyramidine, 3, 4 dimethylpyrazole phosphate (DMPP), 1-amide 2 thiourea (ASU), Ammonium ThioSulphate (ATS), 1H-1, 2-4 Triazole (HPLC), 5-ethylene oxide -3-trichloro-methyl1,2,4 thiodiazole, 3- methylpyrazole (3-MP), 1-carbamoyle-3-methyl –pyrazole (CMP) and neem oil, before drying.
12. The method for preparing the fertilizer composition as claimed in claim 8, wherein a filler selected from the group comprising bentonite, smectite, montmorillonite and other clays is optionally added to the mixture before drying.
13. The method for preparing the fertilizer composition as claimed in claim 8, wherein a hydrophobic compound selected from the group comprising urea aldehydes condensation product such as Urea Formaldehyde (UF) and chemically decomposing compounds such as isobutylidene –Diurea (IBDU) is optionally added to the mixture before drying.
14. The method for preparing the fertilizer composition as claimed in claim 8, wherein the urea is in the form of melted urea or prilled urea.
15. The method for preparing the fertilizer composition as claimed in claim 8, wherein micronutrients are optionally added to the mixture before drying.

Dated this 1st Day of July, 2016

For Sachin Gupta & Associates

(Abhishek Saini)
Agent for Aditya Birla Nuvo Limited
Reg. No. IN/PA-1731
, Description:FIELD OF THE INVENTION
[001] This invention relates to a controlled release fertilizer composition having 10% to 45% nitrogen content. This invention also relates to a method for preparing the said fertilizer.
BACKGROUND OF THE INVENTION
[002] India produces 22 million tonnes of urea annually and imports a further 7 to 8 million tonnes to meet her annual urea requirement for agriculture. Urea efficiency is only 48-51% in dry and hot climates i.e. on 48-51% urea actually goes into meeting the nitrogen needs of plants, the rest being lost to the environment - either to the atmosphere or leaching into ground water or as surface run off in the form of nitrates. This in turn contaminates water bodies, making the water unfit for consumption and spurring the emergence of algal blooms.
[003] In India, urea is subsidized and sold to the farmer at half the cost, causing the Indian government to incur a 50,000 crore subsidy bill annually. There is a need to increase the efficiency of urea i.e. prevent its loss to the environment. Neem oil coated urea has been shown to slow down the hydrolysis of urea/the release of ammonia. However, the slow release does not increase the efficiency of urea. Urea transforms to ammonium cations in the presence of urease enzyme in the soil. Ammonium in turn gets oxidized to nitrites, which get further oxidized to nitrates by various soil micro-organisms. There is a need to anchor the highly mobile nitrate and nitrite anions in the soil. A coating material which is high in carbon content, is organic in nature, doesn’t adversely affect the properties of the soil, and can increase the efficiency of urea by anchoring the highly mobile nitrate and nitrite anions in the soil is highly desirable.
SUMMARY OF THE INVENTION
[004] According to an embodiment of the invention there is provided a controlled release fertilizer composition comprising urea having 10 % to 45% Nitrogen coated with a source of organic carbon and a lignosulfate compound.
[005] According to yet another embodiment of the invention there is provided a method for preparing a controlled release fertilizer composition comprising mixing urea having 10 % to 45% Nitrogen with a source of organic carbon and a lignosulfate compound and then drying the mixture.
DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE PRESENT INVENTION
[006] Urea ordinarily contains 46% Nitrogen. The composition of the present invention can be made with urea such that the overall Nitrogen content in the urea is reduced to 10% to 45% Nitrogen, preferably though 20 to 35%. Optionally, other specialty additives and micronutrients can also be added to coating of the composition.
[007] Preferably, the source of organic carbon is a manure or soil conditioner such as fresh mud from the sugarcane industry or city compost/ waste with organic matter. Fresh soil mixed with cellulose, after extraction of sugar from sugarcane, when allowed to biodegrade for about 45 days, gets converted to soil conditioner having a high organic carbon content and this can be preferentially used in the coating of the composition of the invention.
[008] The lignosulfate compound can be calcium lignosulfate, sodium lignosulfate, ammonium lignosulfate or a combination thereof. The lignosulfate molecule has a large number of charge centers which can be exploited for cation-anion stabilization. Moreover, calcium, ammonium and/or sodium ions are good for the soil. Further, various structurants, carriers and modifiers may also be added to the composition, including but not limited to poly aspartic acid.
[009] Optionally, neem oil is included in the coating before drying the mixture. Optionally, fillers such as bentonite, montmorillonite smectite or other clays are also added to the mixture prior to drying.
[010] One may also use the following additives in the coating for certain specific requirements from time to time. Example, in a paddy field where there is water standing in the field, one may improve the hydrophobicity of the coating of the composition by adding additives like low solubility compounds containing organic nitrogen eg urea aldehydes condensation product such as Urea Formaldehyde (UF) and/or chemically decomposing compounds such as isobutylidene –Diurea (IBDU). Also, physical barrier controls may be used to improve hydrophobicity. Hydrophobicity can be further increased with polymers in which a soluble active material is dispersed in a continuum that restricts the dissolution of the fertilizer. Hydrophobicity can also be increased with organic polymer coatings such as resins or thermoplastic resins or inorganic materials such as sulphur.
[011] Inorganic low solubility compounds can also be added to the organic coating matrix including compounds such as metal ammonium phosphates like Magnesium ammonium phosphate (MgNH4PO4) or acidulated Rock Phosphate.
[012] Nitrification and urease inhibitors can also be added to the composition as these tend to delay the bacterial oxidation of the ammonium ion by depressing the activity of Nitrosomonas bacteria in the soil over a certain period of time (i.e. 2 to 10 weeks). These bacteria transform ammonium ions into nitrite (NO2-), which is further transformed into nitrate (NO3-) by Nitrobacter and Nitrosolobus bacteria. The objective of using a nitrification inhibitor is to control the loss of Nitrate by leaching or the production of Nitrous oxide (N2O) by denitrification from the top soil by keeping Nitrogen in the ammonium form longer and thus improving the efficiency of Nitrogen use. These compounds include 2 chloro-6 (trichloromethyl pyridine, 4 amino 1,2, 4 -6 triazole –HCl, 2,4 diamino -6-trichloro methyltriazine, Dicyandiamide (DCD), Cyanoguanidine (DMPP), ThioUrea, 1 mercapto-1, 2, 4 triazole, 2 amino -4 chloro 6 methyl pyramidine, 3, 4 dimethylpyrazole phosphate (DMPP), 1-amide 2 thiourea (ASU),Ammonium ThioSulphate (ATS), 1H-1, 2-4 Triazole (HPLC), 5-ethylene oxide -3-trichloro-methyl1,2,4 thiodiazole, 3- methylpyrazole (3-MP),1-carbamoyle-3-methyl –pyrazole (CMP) and neem oil.
[013] The lignosulfates act as cation-anion stabilizers and help to anchor the nitrates and nitrites to the soil, thereby reducing the need for higher Nitrogen content in urea. Also, the fertilizer composition of the invention decreases the solubility index of nitrogen containing compounds. Hence, the nitrogen from urea will be available in sufficient amounts when the seed germinates because of the slow release of nitrogen from the composition due to the coating, particularly if neem oil is in the coating. The elution profile showed that elution of urea from the composition of the invention was slower than the elution of urea from neem oil coated urea alone. The composition of the present invention decreases the cost to the farmer since less urea needs to be applied to the crop because of better efficiency of the urea i.e. better anchoring of the nitrogen containing compounds to the soil and slow release of nitrogen due to the coating. The components of the coating function synergistically to allow urea to be released slowly and then anchor the slowly released nitrogen compounds to the soil and prevent their loss to the environment. Improving the efficiency of urea decreases the cost to the farmer and to the government as well in terms of the subsidy costs to the government. Also, the need for more urea production plants will cease if the efficiency of urea improves. This has global implications on the agricultural industry. The composition of the present invention also serves to improve actual yield and also improved leaf greening due to better availability of Nitrogen as shown in the examples below.
[014] The following experimental examples are illustrative of the invention but not limitative of the scope thereof:
Example 1:
[015] 8 kgs of plain urea, i.e. without neem coating, were taken in a high shear mixer and mixed for 2 minutes to make the urea free flowing and partially melted. A fixed quantity of organic manure already sieved through 4 mm sieve and having moisture content of 40-42% and a fixed quantity of commercially available lignosulfates were transferred into the urea pan while slowing down the speed of the rotor to 100 rpm for 5 mins. Thereafter the coated and mixed urea was dried at room temperature or at 35 to 65?C. No water was added during coating. Four samples of urea were made by this method and labelled as T1, T2, T3 and T4. T1 comprised 90g urea, 7.5g soil conditioner and 2.5g lignosulfates. T2 comprised 85g urea, 12.5g soil conditioner and 2.5g lignosulfates. T3 comprised 80g urea, 17.5g soil conditioner and 2.5g lignosulfates. T4 comprised 100g urea. Thus, four grades of fertilizer composition, i.e T1 having approximately 41% Nitrogen from urea and after coating, having approximately 42.03% Nitrogen totally; T2 having approximately 39% Nitrogen and after coating, having approximately 40.35% Nitrogen totally; T3 having approximately 36% Nitrogen and after coating, having approximately 37.27% Nitrogen totally and Control T4 having approximately 46% Nitrogen (standard) were studied in the remaining examples below.
Example 2:
[016] T1, T2, T3 and T4 were evaluated in terms of their effect on a crop of potato. Two 15 sq mtr plots were used for the study. A seed rate of 8-10 Qt/Acre was used at the time of sowing. Spacing was 60x15cms and the design of the study was a randomized block design. RDF (CFG)/15sq mtr was 0.938kgs of a customized fertilizer grade (CFG) + 0.38kgs of fertilizer composition (i.e. T1, T2, T3 and T4). The basal application/15sq mtrs was 0.938kgs CFG and the top dressing/15 sq mtrs was 0.38kgs of fertilizer composition (i.e. T1, T2, T3 and T4). Three treatments of fertilizer composition were given totally, i.e. the first was a basal application of the fertilizer composition along with diammonium phosphate, the next was a first top dressing and this was followed by a second top dressing. Observations were taken at 70 days after sowing and are provided in Table 1 below.

Table 1

Treat No. of Tubers / (15 Sq.M)
Replication 1 (R1) Replication 2 (R2) Mean Mean
(Total Tuber)
Grade A Grade B Grade C Total Tuber Grade A Grade B Grade C Total Tuber Grade A Grade B Grade C All Grades
T1 40 600 997 1637.0 69 926 1171 2166.0 54.5 763.0 1084.0 1901.5
T2 52 652 1103 1807.0 134 905 964 2003.0 93.0 778.5 1033.5 1905.0
T3 9 934 353 1296.0 50 843 1069 1962.0 29.5 888.5 711.0 1629.0
T4 59 936 989 1984.0 105 740 930 1775.0 82.0 838.0 959.5 1879.5
Observations were taken at harvest and are shown in Table2, Table 3 and Table 4 below.
Table 2
Treat Tubers Weight (Kg) / (15 Sq.M)
R1 R2 Mean Mean
(Total Tuber)
Grade A Grade B Grade C Total Tuber Grade A Grade B Grade C Total Tuber Grade A Grade B Grade C All Grades
T1 2.674 15.852 6.458 25.0 4.802 21.13 5.374 31.3 3.7 18.5 5.9 28.1
T2 3.804 17.136 5.836 26.8 9.076 21.994 4.614 35.7 6.4 19.6 5.2 31.2
T3 0.514 23.586 1.776 25.9 3.128 20.874 7.176 31.2 1.8 22.2 4.5 28.5
T4 3.64 22.41 4.322 30.4 7.524 18.994 7.04 33.6 5.6 20.7 5.7 32.0
Table 3. Grade A-Size more than 44mm; Grade B- Size in between 28-44mm; Grade C-Size less than 28mm
Treatments Average Yield (Kg)/(15 Sq.M) Hypothetical Yield/Acre (extrapolated from Yield/15Sq mtr) % Decrease over Control
T1 28.1 74.9 12.2
T2 31.2 83.2 2.5
T3 28.5 76.0 10.9
T4 32.0 85.3 0.0
Table 4

[017] Tables 2, 3 and 4 seem to indicate that T3 shows more number of potatoes in 44 to 28 mm and least in the range of less than 28 mm. T3 has 22% lower Nitrogen compared to T4 (standard urea control). Thus, the cost benefit ratio seem to be highly favourable for this fertilizer composition because the data in the above tables suggest that broadly reducing nitrogen in urea by 22% gives nearly given similar results in terms of yield.
% Difference between replications
Dose & Ferti. pH EC Total N Phosphorous Potash Sulph. S Cu Fe Zn Mn Yield
Trial µS/h Kg/h Avl Kg/h Avl Kg/h As S ppm ppm ppm ppm ppm kg/15 sq.m

T4 8.2 241.0 1566.0 25.1 281.2 16.8 1.05 12.20 7.35 4.00 30.40 10.52
T4 8.0 225.0 2067.0 23.2 264.6 11.4 1.05 5.85 4.75 2.50 33.60

T1 8.7 285.0 1947.0 18.8 248.5 13.3 1.55 12.55 5.59 3.75 25.00 25.2
T1 8.1 227.0 1848.0 20.6 368.0 19.0 1.40 11.90 5.77 5.35 31.30

T2 8.9 192.0 1629.0 22.8 272.3 6.2 1.60 13.20 5.26 3.60 26.80 33.2
T2 8.0 214.0 1847.0 15.5 269.0 17.7 1.95 13.20 8.33 3.85 35.70

T3 8.1 273.0 1534.0 22.2 306.0 12.2 1.25 13.20 5.75 3.60 25.90 20.46
T3 8.4 194.0 1723.0 21.1 278.4 20.8 1.25 13.20 7.15 5.25 31.20

Table 5
[018] From Table 5, it is evident that for T4, higher urea and potash give a higher yield. It is also evident that for T1, higher potash and sulphur give a higher yield. It is further evident that for T2 and T3, higher urea, zinc and sulphur give a higher yield. Also, every replication trial shows a significant difference within itself (10 % for T4 to ~33% for T2 urea with lower Nitrogen content). Further, there is an appreciable difference between the Nitrogen content within each replication, which may have contributed to the difference in yield between the two replications of each fertilizer composition type. It is possible that the nitrogen content in the T4 replication varied so widely because of an existing high nitrogen amount in the soil.
[019] Assuming 2-3% as the error bar, one may conclude that between each of the four fertilizer composition types, the yield differences between all of them for a plot of 15 sq m would get significantly amplified when we multiply this to get Yield per Acre in which case the error bar will also correspondingly increase from 2-3%.
Example 3:
[020] Elution profile of T1, T2, T3 and T4 are shown in the tables below.50 g sample were put in separate funnels into which Whatman Filter Paper No 42 was placed. 100 ml water was used for each washing the time taken for each elution was noted down. The filtrate was analysed, the residue was dried and weighed. The elution results are provided in Table 6 and Table 7 below.
Nitrogen in ppm
N% after coating 1st wash 2nd wash 3rd wash 4th wash 5th wash 6th wash Total N % (1st-6th wash) Residue Wt. (g)
T4 46 148826 72762 3595 255 24.56 2.61 22.54 0
T1 42.03 169188 61801 6053 613 42.27 9.41 23.77 0.8767
T2 40.35 131330 84136 4442 1142 65.13 20.17 22.11 2.946
T3 37.27 135158 80461 17445 3048 250 180 23.65 3.6556

Table 6

Time(min) taken in each Elution
N% after coating 1st wash 2nd wash 3rd wash 4th wash 5th wash 6th wash
T4 46 16 12 11 10 11 10
T1 42.03 24 37 45 120 70 40
T2 40.35 68 330 220 180 150 65
T3 37.27 36 124 260 385 250 180
Table 7
[021] From Table 6, it is clear that T1, T2 and particularly T3 show significantly higher amounts of Nitrogen content in the sixth washing as compared to T4 (standard urea control). Further, T1, T2 and T3 have a significantly higher residue weight left after six washings unlike T4 which indicates that the fertilizer compositions of the invention do not disintegrate as quickly and do not release their nitrogen as quickly as the standard control T4. Further, in Table 6, the values of the total N% in the filtrate obtained from the 1st to 6th washes totally indicate that Nitrogen is released slowly in T1, T2 and T3 as compared to T4 as the elution rates for T1, T2 and T3 are significantly slower than the elution rate of T4.
[022] Table 7 shows that the elution times for T1, T2 and particularly T3 are significantly higher than the elution time for T4. This also indicates that the fertilizer compositions of the invention retain more water than T4 and do not disintegrate as quickly as T4. Water retention is a highly desirable property for a fertilizer as this helps more water to be available to the crop along with the fertilizer, rather than the water being lost as surface run off and sweeping away the nitrogen compounds from urea along with it. Example 4:
[023] In this example, a composition comprising 20% Urea nitrogen was prepared and named T5. Urea comprising 46% Nitrogen (T4) was used as the Control. 5kgs of T5 were prepared using 3260.87 g urea, 1614.13 g organic manure and 125 g lignosulfates. In the procedure for preparing T5, the organic manure fine powder was sieved through a 1mm sieve and dried at 100?C in an oven and 10% moisture was maintained in the organic manure. 3260.87 g plain granular urea was taken in a laboratory mixer and ground at 2200 rpm for 5 minutes. 500 g manure was added to the ground urea and mixed at 250 rpm and further an additional 500g and then 615 g organic manure were added at 1 minute intervals at 250 rpm. Then 250 g commercially available lignosulfates was added to this mixture and mixed at 2000 rpm for 10 minutes to achieve a temperature of 100?C. The mixture remained dry till this point. Then 200 ml solution containing 60 g lignosulfates in water was poured in a slow stream at 100 rpm. The mixer was then run at 1700 rpm for 10 minutes, after which its speed was reduced to 1200 rpm at which point granulation of the composition started and then the mixer was stopped after 15 minutes. Extra water may be added for granulation. Thereafter, the composition was dried under a fan for 30 minutes. The hardness of the composition was found to be more than 2500 g/prill. The product was then sieved and stored in separate polybags based on the size of the prills. The prills were divided based on size into the following groups, prills of size over 1mm, but under 1.8mm were grouped together in one bag, prills of size 1.8mm to 2mm were grouped separated, prills having size of 2.36 to 4mm were grouped in a third bag and a composite bag comprising prills of varying sizes was grouped separately.
[024] The differently sized particles/prills of the composition were then analysed separately. Elution profile of each group based on prill size is shown in Table 8, Table 9 and Table 10 and compared against T4. The percentage of Nitrogen in the urea prills, the total organic contend of the varying sized prills and their elution time was respectively noted in Table 8, Table 9 and Table 10 as shown below.

Nitrogen in ppm
Washing +1.0 mm +1.8 & 2.0 mm +2.36 mm or <4.0 mm Composite T4 standard urea.~ 3 mm
Actual N% 20.81% 19.95% 19.83% 19.55% 45.82%
1st 60167 50843 34183 46317 98085
2nd 19883 26025 21310 17283 0
3rd 6031 3073 3672 5927 0
4th 1461 126 2147 3348 10
5th 159 0 781 1402 4
6th 36 0 318 322 0
7th 4 0 125 53 0
8th 4 0 35 29 0
9th 19 6 14 23 0
10th 15 5 5 20 0
Combined Total N% of 10 washes 8.78% 8.01% 6.26% 7.47% 9.81%
Initial sample wt. taken for Elution (g) 25 25 25 25 25
Dry Residue wt. after 10 washes (g) 6.95 7.614 6.73 7.025 0.162
Results of Residue N% Nil Nil Nil Nil Nil
Table 8

Total Organic Carbon in ppm
Washing +1.0 mm or <1.8 mm +1.8 & 2.0 mm or < 2.36 mm +2.36 mm or <4.0 mm Composite T4 standard urea ~3mm
1st 3705 3549 2262 3354 NA
2nd 2808 3276 2691 2262 NA
3rd 1014 1033 1248 1014 NA
4th 351 292 644 604 NA
5th 176 78 468 351 NA
6th 58 59 205 214 NA
7th 20 49 127 20 NA
8th 52 52 39 39 NA
9th 26 26 26 26 NA
10th 0 0 0 0 NA
Combined Total TOC% of 10 washes 0.82% 0.84% 0.72% 0.79% NA
Results of dry Residue TOC% 38.01% 38.29% 37.96% 38.03% NA

Table 9

Time taken for Elution (minute)
Washing (25 g sample washed with 100 ml demineralized water for each wash) +1.0 mm +1.8 & 2.0 mm +2.36 mm or <4.0 mm Composite T4 standard urea ~3mm
1st 9 8 8 11 14
2nd 31 17 11 17 9
3rd 36 26 13 26 7
4th 29 27 12 36 6
5th 41 29 25 73 7
6th 48 42 24 96 6
7th 48 50 31 120 7
8th 49 55 39 132 6
9th 85 100 55 55 7
10th 135 120 110 50 7
Total Time of 10 washes (min.) 511 474 328 616 76

Table 10
[025] From Table 8, it is clear that the compositions prepared according to an embodiment of the invention have approximately 19.5-20% Nitrogen at the start, however, the amount of Nitrogen eluted after 10 washes was approximately the same for the Control T4 which had 46% Nitrogen at the start compared with the compositions of the invention having less than half that amount of Nitrogen. Also, for the standard urea T4, almost all of the nitrogen gets washed off in the first washing itself, unlike the compositions prepared according to an embodiment of the invention. Further, the compositions prepared according to an embodiment of the invention have a significantly higher residue weight left after ten washings unlike T4 which indicates that the fertilizer compositions of the invention do not disintegrate as quickly and do not release their nitrogen as quickly as the standard control T4. Further, in Table 8, the values of the total N% in the filtrate obtained from the 1st to 10th washes totally indicate that Nitrogen is released slowly in the compositions prepared according to an embodiment of the invention as compared to T4 as the elution rates for the compositions prepared according to an embodiment of the invention are significantly slower than the elution rate of T4 as may be verified by Table 10.
[026] Table 9 shows that the total organic content for the compositions prepared according to an embodiment of the invention is leached out of the composition gradually to provide sustained organic manure to a crop over a long duration.
[027] Table 10 shows that the elution times for the compositions prepared according to an embodiment of the invention are significantly higher than the elution time for T4. This also indicates that the fertilizer compositions of the invention retain more water than T4 and do not disintegrate as quickly as T4. Water retention is a highly desirable property for a fertilizer as this helps more water to be available to the crop along with the fertilizer, rather than the water being lost as surface run off and sweeping away the nitrogen compounds from urea along with it.
[028] It is clear from the above examples that though the fertilizer compositions of the present invention comprise less Nitrogen than standard urea, the said compositions perform equally well or even better than standard urea in terms of crop quality, yield, water retention, and elution profile. The cost benefit of using urea having less than half of the standard amount of nitrogen found in urea is significant and can result in huge savings for farmers and the government which subsidizes urea at present. Further, the environmental benefits of utilizing nitrogen more efficiently from urea cannot be understated. The urea nitrogen in the composition of the invention clearly does not wash off as quickly as nitrogen from standard urea prills. Algal blooms and other problems associated with run off of nitrogen containing compounds from urea utilized inefficiently can thus be avoided. Further, as shown in the experimental examples, crop quality and yield using the compositions of the invention were found to be comparable, and even superior, to the quality and yield of crop utilizing standard urea. The sustained slow release of urea nitrogen to the crop over a longer duration, combined with better efficiency of urea in the compositions of the invention appear to be responsible for these favourable outcomes in crop quality and yield.
[029] The above examples are non-limiting. The invention is defined by the claims that follow.