TECHNICAL FIELD
The present disclosure relates to sustained release fertilizers. More particularly, the present invention relates to a sustained release fertilizer comprising organic carbon backbone and polyphosphate linked with metal ions and nitrogen. BACKGROUND OF THE DISCLOSURE
Of the macronutrients, nitrogen is a key macronutrient source in agriculture particularly for economic crops. Nitrogen is hardest to retain in soil because 50-70% of nitrogen applied using conventional fertilizers is lost to the soil due to evaporation and leaching as NO2 and NH4. Thus, nitrogen utilization efficiency (NUE) by plants is low and greatly increasing the application cost for supplying nitrogen to the plant. To reduce the nitrogen loss, few products are available in the form of nitrification inhibitors or urease inhibitor but the cost is prohibitory for common agriculture. Similarly, the reserve of phosphate is limited. Nitrogen (N) fertilizers particularly contribute to nitrate pollution of waters and the pollution of the atmosphere with nitrous oxide, other oxides of nitrogen, and ammonia which contribute to the "greenhouse effect . The attempts to increase the nitrogen and phosphate utilization efficiency have so far resulted low success. It is articulated that slow release fertilizers would be a solution to increase the macronutrient utilization efficiency particularly nitrogen and phosphate. Currently, phosphorous requirement of plants is supplied in the form of rock phosphate and/or ammonium di-hydrogen phosphate for perennial crops and as triple superphosphate or as a single supper phosphate for short term crops. Although, a high percentage of phosphorous is available in rock phosphate formulations, the available form of phosphate in plants (as H2PO4" or HPO42") is very low due to their adsorption, precipitation or converted to organic forms. Further, the other water soluble phosphorous fertilizer formulations are prohibitively expensive. Therefore, there a need in developing more water soluble phosphorous fertilizer compositions.
Most of the nutrients that a plant needs are dissolved in water and then absorbed by the roots. Ninety-eight percent of these plant nutrients are absorbed from the soil solution, and only about 2 percent is actually extracted from soil particles by the roots. Most nutrient elements are absorbed as charged particles (ions). Nitrogen is absorbed as NO3" or NH4+ from soil or foliage. Nitrates NO3" can leach easily from the soil, if

irrigation water or rain is in excess of plant needs. Similarly, phosphorus is absorbed as the H2PO4" or HPO4" ion. This complex does not leach readily from the soil and is mobile once in the plant. However, phosphorus may leach from soil that is high in bark or peat. Phosphorus is rapidly "fixed" with iron, magnesium, and aluminum on soil particles, when applied under acidic soil conditions. Under alkaline conditions, phosphorus is fixed with calcium and is unavailable to plants.
Further, the conventional fertilizers are applied twice or thrice during the life time of the crops because the actual nutrient present in the fertilizers is not completely available. Due to the over application soil becomes acidic and for every new agriculture, soil needs to be made near neutral with application of alkaline materials. All these practices incur cost to the farmers other than weeding, pesticides etc.
Contemporary research has focused on the use of agronomic techniques in order to improve productivity, in terms of both quality and quantity of products, as well as sustainability of farming by protecting soil resource and reducing the environmental impact. According to the various studies, agricultural production will face major challenges, such as an increasing population, climate change and land degradation. Global assessments of land degradation estimate 15% of the world's total land area shows evidence of damage, mainly as a consequence of erosion, nutrient loss and physical compaction.
Thus, there is still a need in the art for improved sustained release fertilizers. SUMMARY OF THE DISCLOSURE
Provided herein is a sustained release fertilizer comprising organic carbon backbone and polyphosphate linked with metal ions and nitrogen; wherein the fertilizer is characterized by a structure of formula (I) or formula (II):

wherein,
Ri and R2 are independently selected from acetate, glucuronate, cellulose ester, un-dissociated lignin and oligomeric sugar containing mono and di-ammonium phosphate;
R3 is selected from hydrogen, methoxy and O-lignin;
R4 is selected from lignin, ammonium phosphate and urea-phosphate; and
Mi and M2 independently represents divalent or trivalent cation selected from the metal of group II, group III and group VIII of periodic table.
In another aspect, the present disclosure provides a sustained release fertilizer comprising naturally available organic material along with high percentage of both macronutrients and micronutrients.
In yet another aspect, the present disclosure provides a fertilizer for sustained supply of nutrients with single application during the crop cycle.
In yet another aspect, the present disclosure provides a fertilizer, wherein the organic material not only acts as the carrier for the nutrients, but is itself a nutrient material that decomposes to humus thereby by providing texture to soil.
In yet another aspect, the present disclosure provides a fertilizer having about neutral pH.
In yet another aspect, the present disclosure provides a process preparing the sustained release fertilizer; wherein the process comprises:
(a) solubilizing micronutrient source in polyphosphoric acid to get a solution;
(b) solubilizing organic material in the solution of step (a);
(c) adding to the mixture of step (b) a nitrogen containing macronutrient source;
(d) neutralizing the reaction mixture of step (c) to a pH of about 7 by adding ammonia to get a mixture containing the sustained release fertilizer.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
The features of the present disclosure will become fully apparent from the following description taken in conjunction with the accompanying figures. With the understanding that the figures depict only several embodiments in accordance with the

disclosure and are not to be considered limiting of its scope, the disclosure will be described further through use of the accompanying figures:
Fig. 1 illustrates FTIR analysis of sustained release fertilizer according to one embodiment of the disclosure;
Fig. 2: illustrates TGA analysis of sustained release fertilizer according to one embodiment of the disclosure;
Fig. 3: illustrates nitrogen release rate profile of sustained release fertilizer according to one embodiment of the disclosure;
Fig. 4: illustrates phosphate release rate profile of sustained release fertilizer according to one embodiment of the disclosure;
Fig. 5: illustrates zinc release rate profile of sustained release fertilizer according to one embodiment of the disclosure;
Fig. 6: illustrates iron release rate profile of sustained release fertilizer according to one embodiment of the disclosure.
Fig. 7: illustrates pH profile of sustained release fertilizer according to one embodiment of the disclosure;
Fig. 8: illustrates comparative release rate profile of nitrogen and phosphate of the fertilizer with Di-ammonium phosphate (DAP) and urea. DETAILED DESCRIPTION OF THE DISCLOSURE
Before the methods of the present disclosure are described in greater detail, it is to be understood that the methods are not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the methods will be limited only by the appended claims.
Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the methods. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed within the methods, subject to any specifically excluded limit in the stated

range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the methods.
Certain ranges are presented herein with numerical values being preceded by the term "about." The term "about" is used herein to provide literal support for the exact number that it precedes, as well as a number that is near to or approximately the number that the term precedes. In determining whether a number is near to or approximately a specifically recited number, the near or approximating unrecited number may be a number which, in the context in which it is presented, provides the substantial equivalent of the specifically recited number.
Sustained release fertilizers containing organic carbon cross-linked with calcium, nitrogen and phosphate, demonstrate a more sustained release rate when compared to standard nitrogen and/or phosphate fertilizers.
According to various embodiments, the present disclosure provides a sustained release fertilizer comprising organic carbon backbone and polyphosphate linked with metal ions and nitrogen; wherein the fertilizer is characterized by a structure of formula (I) or formula (II):



(II)
wherein,
Ri and R2 are independently selected from acetate, glucuronate, cellulose ester, un-dissociated lignin and oligomeric sugar containing mono and di-ammonium phosphate;
R3 is selected from hydrogen, methoxy and O-lignin;
R4 is selected from lignin, ammonium phosphate and urea-phosphate; and
Mi and M2 independently represents divalent or trivalent cation selected from the metal of group II, group III and group VIII of periodic table.
The organic carbon backbone is obtained from an organic material. The organic material may be a lignocellulose material and the lignocellulose material may be selected from a group comprising hardwood, soft wood and agricultural residue. In certain embodiments, the lignocellulosic biomass is obtained from the fibrous remains of sugarcane and sorghum or any such material of organic origin.
In yet another embodiment, the metal of group II is selected from a group comprising magnesium, calcium and a combination thereof.

In yet another embodiment, the metal of group III is selected from a group comprising boron and aluminium.
In yet another embodiment, the metal of group VIII is selected from a group comprising iron, nickel, copper, zinc and a combination thereof.
In yet another embodiment, the metal source may be from a group comprising metal oxide and micronutrient salt like metal carbonate.
The amounts of nutrients present within the sustained release fertilizer as described herein may vary as follows, where the listed amounts are weight percentages based on the weight of the fertilizer composition:
organic carbon: about 0.2 wt. % - about 10 wt. %; nitrogen derivative (as nitrogen): about 3 wt. % - about 30 wt. %; phosphorus derivative (as P2O5): about 10 wt. % - about 65 wt. %; and micronutrients (other than phosphate): about 0.01 wt. % - about 5 wt. %.
In certain embodiments, the fertilizer comprises organic carbon in an amount from about 1 wt. % to about 8 wt. % or from about 1.8 wt. % to about 7 wt. % or from about 2.6 wt. % to about 6 wt. % or from about 3.2 wt.% to about 5 wt. % or from about 3.8 wt. % to about 4 wt. %.
In certain embodiments, the fertilizer comprises nitrogen in an amount from about 6 wt. % to about 25 wt. % or from about 10 wt. % to about 20 wt. % or from about 15 wt. % to about 20 wt. %.
In certain embodiments, the fertilizer comprises phosphate in an amount from about 14 wt. % to about 60 wt. % or from about 18 wt. % to about 55 wt. % or from about 22 wt. % to about 50 wt. % or from about 40 wt. % to about 50 wt. %. or from about 26 wt. % to about 45 wt. % or from about 30 wt. % to about 40 wt. %.
In certain embodiments, the fertilizer comprises micronutrients (other than phosphate) in an amount from about 0.02 wt.% to about 4 wt.% or from about 0.03 wt. % to about 0.04 wt.% to about 3 wt. % or form about 0.05 wt. % to about 2 wt. % or from about 0.06 wt. % to about 1 wt. %.
Depending on the process of preparation, the composition of the fertilizers may be controlled.

In certain embodiments, the present disclosure provides a sustained release fertilizer comprising naturally available organic material along with high percentage of both macronutrients and micronutrients. The organic material not only acts as a carrier for the nutrients, but is itself a nutrient material that decomposes to humus thereby by providing texture to soil. The fertilizer of the present disclosure may provide sustained supply of nutrients with single application during the crop cycle.
In certain embodiments, the fertilizer according to the present disclosure can be applied to the soil as a basal dose.
The fertilizer of the present disclosure has about a neutral pH thereby making phosphate release at a neutral pH and prevent the possibility of crop burning comprising of organic and inorganic materials.
In certain embodiments, the present disclosure provides a process for preparing a sustained release fertilizer as provided herein; wherein the process comprises:
(a) solubilizing micronutrient source in polyphosphoric acid to get a solution;
(b) solubilizing organic material in the solution of step (a);
(c) adding to the mixture of step (b) a nitrogen containing macronutrient source;
(d) neutralizing the reaction mixture of step (c) to a pH of about 7 by adding ammonia to get a mixture containing the sustained release fertilizer.
The process may further comprise separating the mixture of step (d) to get a residue and filtrate. The residue thus obtained was further dried to get the sustained release fertilizer as a solid. Further, the filtrate was concentrated to get the sustained release fertilizer as a solid.
The polyphosphoric acid used in step (a) is prepared by heating ortho-phosphoric acid at about 270°C. In step (a), the micronutrient source is selected from a group comprising micronutrient oxide and micronutrient salt. The solubilization of micronutrient source in polyphosphoric acid is carried out at a predetermined temperature based on the nutrient being added. In certain embodiments, the temperature is about 5-150°C or about 20-120°C or about 110°C or about 10-25°C. The nutrient source being added may be one or more than one. Then the reaction mixture was cooled to a temperature of about 10-30°C, preferably to a temperature of about 20-25°C, before

adding organic material according to step (b). The organic material is preferably lignocellulose biomass. In certain embodiments, the lignocellulose may be from a group comprising hardwood, soft wood and agricultural residue. In certain embodiments, the lignocellulosic biomass is obtained from the fibrous remains of sugarcane and sorghum or any such material of organic origin.
In step (c), after adding the nitrogen containing macronutrient source, the reaction mixture is stirred at a temperature of about 50-100°C for about 10 minutes to 2 h. In certain embodiments, the temperature is about 55-95°C or about 60-90°C or about 65-85°C or about 70-80°C and stirred for about 15 minutes to 1.5 h or about 20 minutes to 1 h or about 25 minutes to lh or about 30 minutes. In certain embodiments, the nitrogen containing macronutrient source may be selected from a group comprising urea, biuret, ammonia, methylurea and guanylurea. In certain embodiments, the nitrogen containing macronutrient source is urea.
The reaction mixture of step (c) is cooled to about 0-35°C or about 5-30°C or about 10-25°C or about 10-15°C before adding ammonia to it. The ammonia is added, till the reaction mixture attained a pH of about 7, in such a way that the temperature of the neutralized solution is less than about 40°C or less than about 35°C or less than about 30°C, preferably about 20-25°C. The product obtained in step (d) may be used as a seed coating, foliar or soil applications. The neutralized reaction mixture may be further separated, according to its intended end use, to get a residue and filtrate. The obtained residue may be further dried, using methods known in the art, to get the sustained fertilizer as a solid. In certain embodiments, the residue may be dried at a temperature of about 30-60°C, preferably at a temperature of about 40-50°C. On the other hand, the filtrate may be concentrated, using methods known in the art, to get the sustained fertilizer as a solid.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present disclosure, preferred methods and materials are described. For the purposes of the present disclosure, the following terms are defined below.

The articles "a" and "an" are used herein to refer to one or to more than one (i.e. to at least one) of the grammatical object of the article. By way of example, "an element" means one element or more than one element.
As used herein, the term "comprises" or "comprising" is generally used in the sense of include, that is to say permitting the presence of one or more features or components.
Cross-link can include covalent bonds, ionic bonds, electrostatic bonds, Vander Waals bonds and hydrogen bonds.
As used herein, "nutrient" refers to both micronutrients and macronutrients. Non-limiting examples of nutrients include zinc, copper, manganese, boron, calcium, iron, calcium, magnesium, molybdenum, silicon, selenium, phosphate, nitrogen, potassium and sulfur.
As used herein, "micronutrients" refer to elements required in small or trace amounts for plant growth. Non-limiting examples of micronutrients include molybdenum, nickel, copper, zinc, manganese, boron, iron and chloride.
As used herein, "macronutrients" refer to elements typically required in large amounts for plant growth. Non-limiting examples of macronutrients include sulfur, phosphorus, phosphate, magnesium, calcium, potassium, nitrogen, oxygen, carbon and hydrogen.
As used herein, "nutrient use efficiency fertilizer (NUE)" refers to the fertilizer products that can reduce nutrient loss to the environment while increasing the nutrient availability for the plant or crop.
The present disclosure is further described with reference to the following examples, which are only illustrative in nature and should not be construed to limit the scope of the present disclosure in any manner. Starting materials and reagents shown in the process can be obtained from commercial sources or prepared based on procedures described in the literature. EXAMPLES EXAMPLE 1
2.27 moles of phosphoric acid were heated at 270°C for 90 minutes and allowed to cool to room temperature. To this reaction mixture 25 g of sweet sorghum bagasse (approx.

0.2 mm size) was added slowly with constant stirring until the sweet sorghum bagasse completely solubilized. Further, 0.4 moles of urea were added with constant stirring by maintaining the temperature 70°C for 30 minutes. The reaction mixture was neutralized with aqueous ammonia (25%) and adjust the pH to 7.0 at room temperature. The product was filtered under vacuum to collect filtrate and residue. The residue was slowly dried at room temperature and marked as product I. The filtrate was heated at 100°C in a water bath for nearly 3 h to precipitate the mixture. The resultant mixture filtered and the residue was dried at room temperature and marked as product II while filtrate was retained separately and was marked as filtrate I. The obtained products were analyzed and summarized in table 1 below.

EXAMPLE 2
Phosphoric acid (2.27 moles) was heated at 270°C for 90 min and allowed to cool to room temperature. To this, zinc oxide (ZnO, 0.1 moles) was added under constant stirring for complete dissolution at 70°C. This reaction mixture was cooled to room temperature and was added slowly 25 g of sweet sorghum bagasse (about 0.2 mm size). To this mixture urea (0.4 moles) was added with constant stirring by maintaining the temperature at 70°C for 30 minutes. The reaction mixture neutralized with aqueous ammonia (25%) and adjusted the pH to 7.0 at room temperature. The product was filtered under vacuum to collect filtrate and residue. The residue was slowly dried at room temperature and marked as product III. The filtrate was heated at 100°C in a water bath for nearly 3 h to precipitate the mixture. The resultant mixture filtered, and the residue was dried at room temperature and marked as product IV. The filtrate thus obtained was marked as filtrate II. The obtained products were analyzed and summarized in table 1 below.


NA-Not Analyzed EXAMPLE 3
To the polyphosphate as depicted in previous examples, 0.05 moles of ferric oxide was added while stirring and temperature was raised to 90°C for complete dissolution. To this, 0.1 moles of zinc oxide was added, and the temperature was maintained between 70°C while stirring. Once solubilized, 25 g of sweet sorghum bagasse and 0.4 moles of urea were added. The reaction mixture was neutralized with aqueous ammonia (25%) and adjusted the pH to 7.0 at room temperature. The reaction becomes exothermic and reaction was controlled at a temperature of 25°C. The reaction mixture was separated to get residue (product V) which was dried at a constant temperature of 50°C in hot air oven. The filtrate was concentrated at 100°C and dried at a constant temperature to obtain a solid product VI. The obtained products were analyzed and summarized in table 3 below.



EXAMPLE 4
2.27 moles of o-phosphoric acid were heated to 270°C for 90 minutes for generating polyphosphoric acid. The temperature was allowed to drop to room temperature. To this, 0.1 mole of zinc oxide was added under stirring and the temperatures was raised to 70°C till the complete dissolution and further cool it down to room temperature. To this reaction mixture, 25 gm of sweet sorghum bagasse of approximate size 0.2 mm was added to the resultant solution with vigorous stirring at a temperature of 25°C followed by urea (0.4 moles). The reaction mixture was heated to 70°C for 30 minutes with constant stirring. Further, the temperature of the reaction mixture was reduced to 25°C and neutralized with 30% liquor ammonia with vigorous stirring, while keeping the temperature below 25°C, till to reach a pH of 7. The product was filtered under vacuum at room temperature. After filtration, the residue was termed as product VII and dried at 50°C. The filtrate obtained in the process was concentrated at 60°C in a rota-vapor and solid (residue) obtained was kept for air drying and termed as product VIII. The obtained products were analyzed and summarized in table 4 below.




CHARACTERIZATION OF PRODUCTS I TO VIII
The products I to VIII were characterized by FTIR as shown in Fig. 1.
As seen in Fig. 1A, IR spectrum of product I have different characteristic absorption bands at 3200 and 3100 cm"1 corresponding to stretching vibration of O-H and N-H respectively. The band observed at 2796 cm"1 corresponds to stretching vibration of C-H. The bands observed at 985 and 1200 cm"1 correspond to C-O-P, and indicates that there was a bond formation between lignocellulose and phosphoric acid. The bands observed at 895 and 1042 cm"1 assign to PO4"3. The vibrations observed at about 1453 and 1416 cm"1 indicate the formation of ammonium phosphate.
As seen in Fig. IB, IR spectrum of product II has a different characteristic absorption bands at 3200 and 3100 cm"1 corresponding to stretching vibration of O-H and N-H respectively. The band observed at 2798 cm"1 corresponds to stretching vibration of C-H. The bands observed at 985 and 1208 cm"1 correspond to C-O-P, and indicates that there was a bond formation between bagasse and phosphoric acid. The bands observed at 894 and 1043 cm"1 assign to PO4"3. The vibrations observed at about 1451 and 1417 cm"1 indicate the formation of ammonium phosphate.
As seen in Fig. 1C, IR spectrum of product III has a different characteristic absorption bands at 3200 and 3100 cm"1 corresponding to stretching vibration of O-H and N-H respectively. The band observed at 2799 cm"1 corresponds to stretching vibration of C-H. The bands observed at 985 and 1198 cm"1 correspond to C-O-P, and indicate that there was a bond formation between bagasse and phosphoric acid. The bands observed at 894 and 1043 cm"1 assign to PO4"3. The vibrations of ammonia observed at about 1451 and 1417 cm"1 indicate the formation of ammonium phosphate.
As seen in Fig. ID, IR spectrum of product IV has a different characteristic absorption bands at 3200 and 3100 cm"1 corresponding to stretching vibration of O-H and N-H respectively. The band observed at 2800 cm"1 corresponds to stretching vibration of C-H. The bands observed at 984 and 1206 cm"1 correspond to C-O-P, and indicate that

there was a bond formation between bagasse and phosphoric acid. The bands observed at 894 and 1043 cm"1 assign to PO4"3. The vibrations of ammonia observed at about 1446 and 1417 cm"1 indicate that the formation of ammonium phosphate.
As seen in Fig. IE, FTIR analysis of product V shows the characteristics absorption band at 3250 cm"1, 2804 cm"1 correspond to stretching vibrations of O-H and N-H. Peaks observed at 1196 cm"1 and 982 cm"1 correspond to stretching vibrations of P=0 and P-O-(H) respectively. Vibrations at 1668 cm"1 correspond to bending vibrations of N-H (amide II) and the peak at 1789 cm"1 corresponds to C=0 (amide). The peak observed at 552 cm"1 corresponds to N-C-N and the peak appearing at 1444 cm"1 correspond to the stretching vibration of C-N (amide). The peak appearing at 1021 cm"1 is attributed to the stretching vibrations of P-O-P. The peak appearing at 1942 cm"1 corresponds to the stretching vibrations of POO".
As seen in Fig. IF, FTIR Analysis of product VI shows the characteristic absorption band at 3198 cm"1 corresponding to stretching vibrations of O-H. Peaks observed at 1196 cm_1and 974 cm"1 correspond to the stretching vibrations of P=0 and P-0-(H) respectively. Vibrations at 3016 cm"1 correspond to stretching vibrations of N-H (amide II) and the peak at 1790 cm"1 corresponds to C=0 (amide). The peak observed at 561 cm"1 may correspond to the group of N-C-N, the peak appearing at 1442 cm"1 can correspond to the stretching vibration of the group of C-N (amide). The peak appearing at 1038 cm"1 is attributed to the stretching vibrations of P-O-P. The peak appearing at 1942 corresponds to the stretching vibrations of the PO (N). The peak appearing at 2069 cm"1 corresponds to the stretching vibrations of POO".
As seen in Fig. 1G, FTIR Analysis of product VII shows the characteristics absorption band at 3250 cm"1 and 3213 cm"1 correspond the stretching vibrations of O-H and N-H respectively., Peaks observed at 1206 cm"1 and 952 cm"1 correspond to the stretching vibrations of P=0 and P-0-(H) respectively. Vibrations at 1626 cm"1 correspond to bending vibrations of N-H (amide II) and the peak at 1715 cm"1 corresponds to C=0 (amide). The peak observed at 552 cm"1 may correspond to the group of N-C-N, the peak appearing at 1403 cm"1 can correspond to the stretching vibration of the group of C-N (amide). The peak appearing at 1055 cm"1 is attributed to the stretching

vibrations of P-O-P. The peak appearing at 2204 cm"1 corresponds to the stretching vibrations of POO".
As seen in Fig. 1H, FTIR Analysis of product VIII shows the characteristics absorption band at 3200 cm"1 corresponding to the stretching vibrations of O-H. Peaks observed at 1196 cm"1 and 969 cm"1 correspond to the stretching vibrations of P=0 and P-0-(H) respectively. Vibrations at 3112 cm"1 correspond to stretching vibrations of N-H (amide II) and the peak at 1715 cm"1 corresponds to C=0 (amide). The peak observed at 561 cm"1 may correspond to the group of N-C-N, the peak appearing at 1461 cm"1 can correspond to the stretching vibration of the group of C-N (amide). The peak appearing at 1094 cm"1 is attributed to the stretching vibrations of P-O-P. The peak appearing at 1941 corresponds to the stretching vibrations of the PO (N). The peak appearing at 2279 cm"1 corresponds to the stretching vibrations of POO". THERMOGRAVIMETRIC ANALYSIS (TGA):
TGA of the products I-VIII can be seen in Fig. 2.
Fig. 2A illustrates TGA of product I and its related derivative thermograms (DTG). The thermo-gravimetric analysis performed in the temperature ranging from 30 to 800°C at a rate of 10°C/min under a nitrogen atmosphere. The derivative plot shows decomposition temperatures of the product in various stages. In the first stage of temperature, 30°C to 174°C, the losses are due to evaporation of moisture and volatile gases. The second decomposition stage is expected to be pyrolysis and the evolution of combustible gases. The compound started to decompose at 174°C. The greater stability of product I is evidenced from DTG curves, where the decomposition peak temperature of product I was at 574.73°C.
Fig. 2B illustrates thermal stability of product II and related derivative thermograms (DTG). The thermo-gravimetric analysis performed in the temperature range from 30 to 800°C at a rate of 10°C/min under a nitrogen atmosphere. The derivative plot shows decomposition temperatures of the product in various stages. In the first stage, the losses are due to evaporation of moisture and volatile gases. The second decomposition stage is expected to be pyrolysis and evolution of combustible gases. The compound started to decompose at 173.6°C. The greater stability of II is evidenced from DTG curves, where the decomposition peak temperature was at 562.63°C.

Fig. 2C illustrates thermal stability of product III related derivative thermograms (DTG). The thermo-gravimetric analysis performed in the temperature range from 30 to 900°C at a rate of 10°C/min under a nitrogen atmosphere. The derivative plot shows decomposition temperatures of the product in various stages. In the first stage, the losses are due to evaporation of moisture and volatile gases. The second decomposition stage is expected due to the pyrolysis and the evolution of combustible gases. The greater thermal stability is evident from the DTG curve where the decomposition curve is obtained at 729.94°C.
Fig. 2D illustrates thermal stability of product IV and related derivative thermograms (DTG). The thermo-gravimetric analysis performed in the temperature range from 30 to 900°C at a rate of 10°C/min under a nitrogen atmosphere. The derivative plot shows decomposition temperatures of the product in various stages. In the first stage, the losses are due to evaporation of moisture and volatile gases. The second decomposition stage is expected due to the pyrolysis and the evolution of combustible gases. The greater thermal stability is evident from the DTG curve where the decomposition curve is obtained at 730.3°C.
Fig. 2E illustrates thermal stability of product V related derivative thermograms (DTG). The thermo-gravimetric analysis performed in the temperature range from 30 to 900°C at a rate of 10°C/min under a nitrogen atmosphere. The derivative plot shows decomposition temperatures of the product in various stages. In the first stage, the losses are due to evaporation of moisture and volatile gases. The second decomposition stage is expected due to the pyrolysis and the evolution of combustible gases. The greater thermal stability is evident from the DTG curve where the decomposition curve is obtained at 899.48°C.
Fig. 2F illustrates thermal stability of product VI and related derivative thermograms (DTG). The thermo-gravimetric analysis performed in the temperature range from 30 to 900°C at a rate of 10°C/min under a nitrogen atmosphere. The derivative plot shows decomposition temperatures of the product in various stages. In the first stage, the losses are due to evaporation of moisture and volatile gases. The second decomposition stage is expected due to the pyrolysis and the evolution of combustible

gases. The greater thermal stability is evident from the DTG curve where the decomposition curve is obtained at 899.48°C.
Fig. 2G illustrates thermal stability of product VII and related derivative thermograms (DTG). The thermo-gravimetric analysis performed in the temperature range from 30 to 900°C at a rate of 10°C/min under a nitrogen atmosphere. The derivative plot shows decomposition temperatures of the product in various stages. In the first stage, the losses are due to evaporation of moisture and volatile. The second decomposition stage is expected due to the pyrolysis and the evolution of combustible gases. The greater thermal stability is evident from the DTG curve where the decomposition curve is obtained at 625.58°C.
Fig. 2H illustrates thermal stability of product VIII and related derivative thermograms (DTG). The thermo-gravimetric analysis performed in the temperature range from 30 to 900°C at a rate of 10°C/min under a nitrogen atmosphere. The derivative plot shows decomposition temperatures of the product in various stages. In the first stage, the losses are due to evaporation of moisture and volatile gases. The second decomposition stage is expected due to the pyrolysis and the evolution of combustible gases. The greater thermal stability is evident from the DTG curve where the decomposition curve is obtained at 640.1°C.
Fig. 21 illustrates thermal stability of cellulose and related derivative thermograms (DTG). The thermo-gravimetric analysis performed in the temperature range from 30 to 800°C at a rate of 10°C/min under a nitrogen atmosphere. The derivative plot shows decomposition temperatures of the product in various stages. In the first stage, the losses are due to evaporation of moisture and volatile gases. The second decomposition stage is expected due to the pyrolysis and the evolution of combustible gases. The greater thermal stability is evident from the DTG curve where the decomposition curve is obtained at 334.22°C.
Fig. 2J illustrates thermal stability of lignin and related derivative thermograms (DTG). The thermo-gravimetric analysis performed in the temperature range from 30 to 900°C at a rate of 10°C/min under a nitrogen atmosphere. The derivative plot shows decomposition temperatures of the product in various stages. In the first stage, the losses are due to evaporation of moisture and volatile gases. The second decomposition stage is
on

expected due to the pyrolysis and the evolution of combustible gases. The greater thermal stability is evident from the DTG curve where the decomposition curve is obtained at 316.47°C.
Fig. 2K illustrates thermal stability of lignin and related derivative thermograms (DTG). The thermo-gravimetric analysis performed in the temperature range from 30 to 900°C at a rate of 10°C/min under a nitrogen atmosphere. The derivative plot shows decomposition temperatures of the product in various stages. In the first stage, the losses are due to evaporation of moisture and volatile gases. The second decomposition stage is expected due to the pyrolysis and the evolution of combustible gases. The greater thermal stability is evident from the DTG curve where the decomposition curve is obtained at 353.59°C.
The thermal stability analysis of the products I to VIII are entirely different from the native structure of cellulose, lignin or biomass. This indicates that new products were developed upon contacting organic matter such as lignocellulosic biomass with phosphoric acid, nitrogen source and micronutrients. RELEASE STUDY OF NUTRIENTS:
Leaching columns were used to quantify the release of macronutrient such as nitrogen, phosphate and micronutrients over time and comparison made with conventional fertilizers such as di-ammonium phosphate, urea, etc. Acid treated neutralized soil sample of 2 mm packed in a tubular column of approximately 5 x 50 cm and column is attached with tubing from the bottom to collect the leachate. Immediately, after adding the fertilizer on top of the column, water was added at a constant rate so that the top of the column remains moistened. Samples collected at different interval and analyzed. Nitrogen Release Profile of Products I-VIII:
As seen in Fig. 3 A, product I steadily released almost 98% nitrogen over 240 h (10 days).
As seen in Fig. 3B, a maximum of about 35% nitrogen released from product II within 24 h and remaining nitrogen released slowly over the period of study and showed the slow and sustained release of nutrients.

As seen in Fig. 3C, a maximum of about 55% nitrogen released from product III within 24 h and remaining nitrogen released slowly over the period of 168 h (7 days).
As seen in Fig. 3D, a maximum of about 60% nitrogen released from product IV within 24 h and remaining nitrogen released slowly over the period of 144 h (6 days).
As seen in Fig. 3E, the product V steadily released about 80% nitrogen over 240 h (10 days).
As seen in Fig. 3F, product VI steadily released about 96% nitrogen over 240 h (10 days).
As seen in Fig. 3G, product VII steadily released about 96% nitrogen over 240 h (10 days).
As seen in Fig. 3H, product VIII steadily released about 50 % of nitrogen over 192 h (8 days). Phosphate Release Profile of Products I-VIII:
As seen in Fig. 4A, a maximum of 45% of phosphate released within 24 h from product I and after that the release of phosphate is linear over the period of time.
As seen in Fig. 4B, about 75% phosphate released within 24 h from product II and remaining phosphate released in a sustainable manner over 144 h.
As seen in Fig. 4C, about 12% phosphate released within 24 h from product III and remaining phosphate released slowly over the period of 48 h (2 days).
As seen in Fig. 4D, about 38% phosphate released within 24 h from product IV and remaining phosphate released slowly over the period of 48 h (2 days).
As seen in Fig. 4E, about 38% phosphate released within 12 h from product V and remaining phosphate released slowly over the period of 72 h (3 days).
As seen in Fig. 4F, about 15% phosphate released within 24 h from product VI and remaining phosphate of about 91% released slowly over the 78 h.
As seen in Fig. 4G, a maximum of about 43% phosphate released within 24 h from product VII and the remaining phosphate release is linear over the period of time.
As seen in Fig. 4H, a maximum of about 74% phosphate released from product VIII, and after that the release of phosphate is linear over the period of time.

Zinc Release Profile of Products III-VIII:
As seen in Fig. 5A, about 63% zinc released within 24 h from product III and the remaining zinc present 48 h.
As seen in Fig. 5B, about 100% zinc released within 12 h from product IV.
As seen in Fig. 5C, about 100%) zinc released within 9 h from product V.
As seen in Fig. 5D, about 60%> zinc released in 144 h from product VI, and the remaining zinc released in time dependent manner beyond 144 h.
As seen in Fig. 5E, about 75% zinc released within 10 h from product VII and reached a plateau.
As seen in Fig. 5F, about 80%> zinc released within 120 h from product VIII and reached a plateau. Iron Release Profile of products V-VI:
As seen in Fig. 6A, about 57% of iron released within 72 h (3 days) from product V, and the remaining released over the time.
As seen in Fig. 6B, about 100%) iron released from product VI within 72 h. pH Profile During Release of Nutrients:
The pH profile during release of nutrients is shown in Fig. 7A-F. COMPARATIVE ANALYSIS OF NUTRIENT RELEASE WITH DAP AND UREA FOR PHOSPHATE AND NITROGEN RELEASE:
As seen in Fig. 8A, the nitrogen release of product VII is 12 times slower than urea and 7 times slower than DAP. Similarly, the nitrogen release of product VIII is 6 times slower than urea and 3.5 times slower than DAP.
As seen in Fig. 8B, the phosphorous release of product VII is 4 times faster than DAP. Similarly, the phosphorous release of product VIII is 6 times faster than DAP.
The results clearly demonstrated that the present invention surprisingly found the uses of macronutrient and micronutrients with organic matter to develop novel products which is sustained release of nutrients over a period of time and providing a solution by employing micronutrients which are not precipitating even in the presence of phosphate. Organic matter present in the products capable of providing bonding with the nutrients in presence of phosphate in the form of polyphosphate and during the release of nutrients pH of the products remain neutral which is the additional benefit over the known

products such as urea or DAP and therefore soil remain fertile without addition of any base material which usually found in most of the agriculture soil after application the soil become acidic. FIELD TRIAL DATA
To evaluate the performance of the products, field trials conducted at Directorate of Rice Research, Hyderabad, India on rice (Variety Vardhana) in three replications for both kharif and rabi seasons. The products selected were III and IV (Example 2). Randomized block of size 4 mt x 3 mt selected for the study. The study conducted with single basal application and compared with the standard fertilizer application and no fertilizer application. Except for supplementing nitrogen at basal dose to compensate the amount of nitrogen at the basal dose, other conditions remain same for all the applications. The harvested data clearly showed that grain yield is superior to the recommended doses of fertilizers and even at application of 50% of the fertilizer, the yield is similar or better than the recommended doses of fertilizer application wherein there is nearly 20% increase in grain yield compared to the recommended fertilizer dose: 120: 60: 40 kg /ha NPK at 100%) dose. Also, the straw yield is increased significantly over the control. The fertilizer is applied as a basal dose. Following is the protocol followed in field trial study.



# As per recommended practices (1 basal and 2 splits) % GY*= Percentage of grain yield over controls MOP = Murate of Potash ADVANTAGES OF THE PRESENT INVENTION
1. The fertilizer of the present disclosure provides nutrients for an extended period
of time compared to individual nitrogen or phosphate fertilizers or any known
fertilizers and found to provide better growth and yields in plants when used in a
variety of ways such as seed coating, foliar or soil applications.
2. The fertilizer of the present disclosure in solid complex form, containing
macronutrients and essential minerals is completely soluble in water and release
the nutrients present therein in a sustained manner which makes the fertilizers
high use efficiency fertilizers. This soluble fertilizer can be used for foliar
application, and can be conventional admixed to solution to improve the retention
of the products for longer duration of time for adsorption and translocation inside
the leaf for cellular activities.
3. The fertilizer of the present disclosure is precipitate free, and water soluble which
provides nutrients to the plants for an extended period of time.
4. The fertilizer of the present disclosure has neutral or near neutral pH to protect the
plants from acid burns.
5. The fertilizer of the present disclosure can be used as a single application
6. Availability of micronutrients in presence of phosphate is maximized.
Although the foregoing disclosure has been described in some detail by way of illustration and examples for purposes of clarity of understanding, it is readily apparent to

those of ordinary skill in the art in light of the teachings of this disclosure that certain changes and modifications may be made thereto without departing from the spirit or scope of the appended claims.
Accordingly, the preceding merely illustrates the principles of the disclosure. It will be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the disclosure and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended to aid the reader in understanding the principles of the disclosure and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the disclosure as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. The scope of the present disclosure, therefore, is not intended to be limited to the exemplary embodiments shown and described herein. Rather, the scope and spirit of present disclosure is embodied by the appended claims.

1. A sustained release fertilizer comprising organic carbon backbone and
polyphosphate linked with metal ions and nitrogen; wherein the sustained release fertilizer is characterized by a structure of formula (I) or formula (II):



(II)
wherein,
Ri and R2 are independently selected from acetate, glucuronate, cellulose ester, un-dissociated lignin and oligomeric sugar containing mono and di-ammonium phosphate;
R3 is selected from hydrogen, methoxy and O-lignin;
R4 is selected from lignin, ammonium phosphate and urea-phosphate; and
Mi and M2 independently represents divalent or trivalent cation selected from the metal of group II, group III and group VIII of periodic table.
2. The sustained release fertilizer as claimed in claim 1, wherein the divalent or
trivalent cation is selected from a group comprising iron, magnesium, aluminium, zinc,
boron, cobalt, manganese, molybdenum and a combination thereof.
3. The sustained release fertilizer as claimed in claim 1, wherein the fertilizer
comprises at least one nutrient from the nutrients listed below:
organic carbon: 0.2 wt. % - 9 wt. %;
nitrogen derivative (as nitrogen): 10 wt. % - 28 wt. %;
phosphorus derivative (as P2O5): 10 wt. % - 65 wt. %; and

micronutrients (other than phosphate): 0.01 wt. % - 5 wt. %.
4. The sustained release fertilizer as claimed in claim 1, wherein the organic carbon backbone is obtained from an organic material.
5. The sustained release fertilizer as claimed in claim 1, wherein the fertilizer application is a basal application.
6. The sustained release fertilizer as claimed in claim 1, wherein pH of the fertilizer is about neutral pH.
7. A process for preparing a sustained release fertilizer as claimed in claim 1; wherein the process comprises:

(a) solubilizing micronutrient source in polyphosphoric acid to get a solution;
(b) solubilizing organic material in the solution of step (a);
(c) adding to the mixture of step (b) a nitrogen containing macronutrient source;
(d) neutralizing the reaction mixture of step (c) to a pH of about 7 by adding ammonia to get a mixture containing the sustained release fertilizer.

8. The process as claimed in claim 7, may further comprise separating the mixture of step (d) to get a residue and filtrate.
9. The process as claimed in claim 7, wherein micronutrient source in step (a) is selected from a group comprising micronutrient oxide and micronutrient salt.
10. The process as claimed in claim 7, wherein solubilization of micronutrient source in polyphosphoric acid is carried out at a temperature of about 5-150°C.
11. The process as claimed in claim 7, wherein the organic material is lignocellulosic biomass.
12. The process as claimed in claim 7, wherein step (b) takes place at a temperature of about 10-30°C.
13. The process as claimed in claim 7, wherein nitrogen containing macronutrient source in step (c) is selected from a group comprising urea, biuret, ammonia, methylurea and guanylurea.
14. The process as claimed in claim 13, wherein the nitrogen containing macronutrient source is urea.

15. The process as claimed in claim 7, wherein the reaction mixture in step (c) is stirred at a temperature of about 50-100°C for about 10 minutes to 2 h.
16. The process as claimed in claim 15, wherein the reaction mixture is stirred at a temperature of about 70-80°C for about 30 minutes.
17. The process as claimed in claim 7, wherein neutralization is carried out at a temperature of about 0-35°C, preferably at about 10-15°C.
18. The process as claimed in claim 7, wherein neutralization is carried out in such a way that the temperature of the neutralized solution is less than about 40°C.
19. A sustained release fertilizer obtained by the process as claimed in any of the claims 7-18.
Dated this 09th day of February, 2018