PH12015501297B1 - Composition and method for sustained release of agricultural macronutrients - Google Patents
Composition and method for sustained release of agricultural macronutrients Download PDFInfo
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- PH12015501297B1 PH12015501297B1 PH12015501297A PH12015501297A PH12015501297B1 PH 12015501297 B1 PH12015501297 B1 PH 12015501297B1 PH 12015501297 A PH12015501297 A PH 12015501297A PH 12015501297 A PH12015501297 A PH 12015501297A PH 12015501297 B1 PH12015501297 B1 PH 12015501297B1
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- urea
- hap
- nanoparticles
- macronutrient
- plant
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- 235000021073 macronutrients Nutrition 0.000 title claims abstract description 57
- 239000000203 mixture Substances 0.000 title claims abstract description 21
- 238000000034 method Methods 0.000 title claims description 41
- 238000013268 sustained release Methods 0.000 title claims description 7
- 239000012730 sustained-release form Substances 0.000 title claims description 7
- 239000002105 nanoparticle Substances 0.000 claims abstract description 114
- 230000003050 macronutrient Effects 0.000 claims abstract description 39
- 239000002689 soil Substances 0.000 claims abstract description 39
- 239000003337 fertilizer Substances 0.000 claims abstract description 34
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910052588 hydroxylapatite Inorganic materials 0.000 claims abstract description 11
- XYJRXVWERLGGKC-UHFFFAOYSA-D pentacalcium;hydroxide;triphosphate Chemical compound [OH-].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O XYJRXVWERLGGKC-UHFFFAOYSA-D 0.000 claims abstract description 11
- 229910019142 PO4 Inorganic materials 0.000 claims abstract description 10
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims abstract description 9
- 239000010452 phosphate Substances 0.000 claims abstract description 9
- XSQUKJJJFZCRTK-UHFFFAOYSA-N urea group Chemical group NC(=O)N XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 155
- 239000004202 carbamide Substances 0.000 claims description 89
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 31
- 241000196324 Embryophyta Species 0.000 claims description 25
- 239000002114 nanocomposite Substances 0.000 claims description 21
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 15
- 239000006185 dispersion Substances 0.000 claims description 15
- 244000269722 Thea sinensis Species 0.000 claims description 12
- 240000007594 Oryza sativa Species 0.000 claims description 9
- 239000007787 solid Substances 0.000 claims description 8
- 235000006468 Thea sinensis Nutrition 0.000 claims description 5
- 240000008042 Zea mays Species 0.000 claims description 4
- 235000002017 Zea mays subsp mays Nutrition 0.000 claims description 4
- 150000001875 compounds Chemical class 0.000 claims description 4
- 244000060011 Cocos nucifera Species 0.000 claims description 2
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 claims description 2
- 235000016383 Zea mays subsp huehuetenangensis Nutrition 0.000 claims description 2
- 235000005822 corn Nutrition 0.000 claims description 2
- 235000009973 maize Nutrition 0.000 claims description 2
- 244000286663 Ficus elastica Species 0.000 claims 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 46
- 229910052757 nitrogen Inorganic materials 0.000 description 26
- 239000002131 composite material Substances 0.000 description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 18
- 239000002245 particle Substances 0.000 description 16
- 230000012010 growth Effects 0.000 description 15
- 235000011007 phosphoric acid Nutrition 0.000 description 15
- 239000000243 solution Substances 0.000 description 12
- 239000011575 calcium Substances 0.000 description 11
- 239000000843 powder Substances 0.000 description 11
- 230000015572 biosynthetic process Effects 0.000 description 9
- 238000001878 scanning electron micrograph Methods 0.000 description 9
- 238000011282 treatment Methods 0.000 description 9
- 241000134253 Lanka Species 0.000 description 8
- 238000003756 stirring Methods 0.000 description 8
- 235000007164 Oryza sativa Nutrition 0.000 description 7
- 238000004458 analytical method Methods 0.000 description 7
- 230000003993 interaction Effects 0.000 description 7
- 235000009566 rice Nutrition 0.000 description 7
- 238000003786 synthesis reaction Methods 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 238000009472 formulation Methods 0.000 description 6
- 239000008187 granular material Substances 0.000 description 6
- 239000012071 phase Substances 0.000 description 6
- 230000008635 plant growth Effects 0.000 description 6
- 235000013339 cereals Nutrition 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 238000011068 loading method Methods 0.000 description 5
- 239000011785 micronutrient Substances 0.000 description 5
- 235000013369 micronutrients Nutrition 0.000 description 5
- 235000015097 nutrients Nutrition 0.000 description 5
- 239000011148 porous material Substances 0.000 description 5
- 238000003980 solgel method Methods 0.000 description 5
- 238000001179 sorption measurement Methods 0.000 description 5
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 4
- 238000001157 Fourier transform infrared spectrum Methods 0.000 description 4
- 238000001069 Raman spectroscopy Methods 0.000 description 4
- 150000001412 amines Chemical class 0.000 description 4
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 4
- 239000000920 calcium hydroxide Substances 0.000 description 4
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 4
- 235000011116 calcium hydroxide Nutrition 0.000 description 4
- 239000004927 clay Substances 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
- 238000002386 leaching Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000002086 nanomaterial Substances 0.000 description 4
- 239000007921 spray Substances 0.000 description 4
- 238000005287 template synthesis Methods 0.000 description 4
- 238000003917 TEM image Methods 0.000 description 3
- 230000002378 acidificating effect Effects 0.000 description 3
- 150000001408 amides Chemical class 0.000 description 3
- 238000012512 characterization method Methods 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 239000011572 manganese Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- 239000002102 nanobead Substances 0.000 description 3
- 239000005416 organic matter Substances 0.000 description 3
- 238000005507 spraying Methods 0.000 description 3
- 239000000725 suspension Substances 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 2
- 235000021307 Triticum Nutrition 0.000 description 2
- 244000098338 Triticum aestivum Species 0.000 description 2
- 239000011324 bead Substances 0.000 description 2
- 210000000988 bone and bone Anatomy 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000000460 chlorine Substances 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 230000001186 cumulative effect Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 2
- GUJOJGAPFQRJSV-UHFFFAOYSA-N dialuminum;dioxosilane;oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Al+3].[Al+3].O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O GUJOJGAPFQRJSV-UHFFFAOYSA-N 0.000 description 2
- 229920001971 elastomer Polymers 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- -1 hydroxyl ions Chemical class 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 230000002262 irrigation Effects 0.000 description 2
- 238000003973 irrigation Methods 0.000 description 2
- 239000003446 ligand Substances 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 239000002609 medium Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052901 montmorillonite Inorganic materials 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 239000011591 potassium Substances 0.000 description 2
- 238000000634 powder X-ray diffraction Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 102000004169 proteins and genes Human genes 0.000 description 2
- 108090000623 proteins and genes Proteins 0.000 description 2
- 238000012827 research and development Methods 0.000 description 2
- 239000011669 selenium Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 230000002459 sustained effect Effects 0.000 description 2
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- 229920001661 Chitosan Polymers 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 235000013162 Cocos nucifera Nutrition 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229920000742 Cotton Polymers 0.000 description 1
- 244000068988 Glycine max Species 0.000 description 1
- 235000010469 Glycine max Nutrition 0.000 description 1
- 235000007688 Lycopersicon esculentum Nutrition 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 244000070406 Malus silvestris Species 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- UEZVMMHDMIWARA-UHFFFAOYSA-N Metaphosphoric acid Chemical compound OP(=O)=O UEZVMMHDMIWARA-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- 244000061176 Nicotiana tabacum Species 0.000 description 1
- 235000002637 Nicotiana tabacum Nutrition 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 description 1
- 241000233855 Orchidaceae Species 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 241000985694 Polypodiopsida Species 0.000 description 1
- 229920002396 Polyurea Polymers 0.000 description 1
- 238000001237 Raman spectrum Methods 0.000 description 1
- 240000000111 Saccharum officinarum Species 0.000 description 1
- 235000007201 Saccharum officinarum Nutrition 0.000 description 1
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 1
- 240000003768 Solanum lycopersicum Species 0.000 description 1
- 240000006394 Sorghum bicolor Species 0.000 description 1
- 235000011684 Sorghum saccharatum Nutrition 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 229920000615 alginic acid Polymers 0.000 description 1
- 235000010443 alginic acid Nutrition 0.000 description 1
- 125000003368 amide group Chemical group 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 235000021016 apples Nutrition 0.000 description 1
- 239000013011 aqueous formulation Substances 0.000 description 1
- 239000012736 aqueous medium Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000000975 bioactive effect Effects 0.000 description 1
- 229920001222 biopolymer Polymers 0.000 description 1
- 230000008468 bone growth Effects 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 229910001424 calcium ion Inorganic materials 0.000 description 1
- KIZFHUJKFSNWKO-UHFFFAOYSA-M calcium monohydroxide Chemical compound [Ca]O KIZFHUJKFSNWKO-UHFFFAOYSA-M 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 230000009918 complex formation Effects 0.000 description 1
- 238000013270 controlled release Methods 0.000 description 1
- 244000038559 crop plants Species 0.000 description 1
- 238000002447 crystallographic data Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 235000013399 edible fruits Nutrition 0.000 description 1
- 238000002003 electron diffraction Methods 0.000 description 1
- 238000002524 electron diffraction data Methods 0.000 description 1
- 238000000921 elemental analysis Methods 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 238000005538 encapsulation Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 244000037666 field crops Species 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 230000007773 growth pattern Effects 0.000 description 1
- 230000002363 herbicidal effect Effects 0.000 description 1
- 239000004009 herbicide Substances 0.000 description 1
- 125000005842 heteroatom Chemical group 0.000 description 1
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 239000002077 nanosphere Substances 0.000 description 1
- 150000002829 nitrogen Chemical class 0.000 description 1
- 239000000618 nitrogen fertilizer Substances 0.000 description 1
- 238000000643 oven drying Methods 0.000 description 1
- 239000000575 pesticide Substances 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 229920000768 polyamine Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000001144 powder X-ray diffraction data Methods 0.000 description 1
- 230000006916 protein interaction Effects 0.000 description 1
- 230000005588 protonation Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 239000012429 reaction media Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000002786 root growth Effects 0.000 description 1
- 229910052711 selenium Inorganic materials 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 239000012798 spherical particle Substances 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 239000002352 surface water Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- JBQYATWDVHIOAR-UHFFFAOYSA-N tellanylidenegermanium Chemical compound [Te]=[Ge] JBQYATWDVHIOAR-UHFFFAOYSA-N 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 235000013311 vegetables Nutrition 0.000 description 1
- 230000035899 viability Effects 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05B—PHOSPHATIC FERTILISERS
- C05B19/00—Granulation or pelletisation of phosphatic fertilisers, other than slag
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05B—PHOSPHATIC FERTILISERS
- C05B17/00—Other phosphatic fertilisers, e.g. soft rock phosphates, bone meal
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05C—NITROGENOUS FERTILISERS
- C05C9/00—Fertilisers containing urea or urea compounds
- C05C9/005—Post-treatment
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05G—MIXTURES OF FERTILISERS COVERED INDIVIDUALLY BY DIFFERENT SUBCLASSES OF CLASS C05; MIXTURES OF ONE OR MORE FERTILISERS WITH MATERIALS NOT HAVING A SPECIFIC FERTILISING ACTIVITY, e.g. PESTICIDES, SOIL-CONDITIONERS, WETTING AGENTS; FERTILISERS CHARACTERISED BY THEIR FORM
- C05G5/00—Fertilisers characterised by their form
- C05G5/30—Layered or coated, e.g. dust-preventing coatings
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05G—MIXTURES OF FERTILISERS COVERED INDIVIDUALLY BY DIFFERENT SUBCLASSES OF CLASS C05; MIXTURES OF ONE OR MORE FERTILISERS WITH MATERIALS NOT HAVING A SPECIFIC FERTILISING ACTIVITY, e.g. PESTICIDES, SOIL-CONDITIONERS, WETTING AGENTS; FERTILISERS CHARACTERISED BY THEIR FORM
- C05G5/00—Fertilisers characterised by their form
- C05G5/40—Fertilisers incorporated into a matrix
-
- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05G—MIXTURES OF FERTILISERS COVERED INDIVIDUALLY BY DIFFERENT SUBCLASSES OF CLASS C05; MIXTURES OF ONE OR MORE FERTILISERS WITH MATERIALS NOT HAVING A SPECIFIC FERTILISING ACTIVITY, e.g. PESTICIDES, SOIL-CONDITIONERS, WETTING AGENTS; FERTILISERS CHARACTERISED BY THEIR FORM
- C05G5/00—Fertilisers characterised by their form
- C05G5/45—Form not covered by groups C05G5/10 - C05G5/18, C05G5/20 - C05G5/27, C05G5/30 - C05G5/38 or C05G5/40, e.g. soluble or permeable packaging
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Pest Control & Pesticides (AREA)
- Fertilizers (AREA)
Abstract
A fertilizer composition wherein a nitrogen containing macronutrient is adsorbed on the surface of hydroxyapatite phosphate nanoparticles. Said fertilizer composition slowly releases the nitrogen containing macronutrient to soil.
Description
Then, H3PO4 (0.6 M, 250.0 ml) was added drop wise while stirring at 750 rpm.
The solution was further stirred for 10 minutes after completion of the addition of phosphoric acid to yield a stable dispersion containing HAP-urea nanoparticles (HAP:Urea ratio 1:1). In a similar manner, HAP-urea nanoparticles were prepared with HAP:Urea ratios of 1:3, 1:4, 1:5 and 1:6 resulting in a foliage fertilizer formulation.
The dispersions that resulted can be dried in an oven at 60 °C or preferably flash dried to get the solid fertilizer compositions as chips or granules.
These resulting chips or granules can be ground into a powder. b) Morphology of HAP-Urea Nanocomposite: Template Synthesis Method
As seen in Figure 1 (a), bead like nanoparticles (diameter 10 — 20 nm with uniform size) formed. The orientation attachment or directional growth was delayed as a result of the presence of surface modifiers such as amines, di- amines and amide group containing organic molecules which delay the directional growth of bead-like nanoparticles. However, with time it was observed (see Figure 1(b)) that the bead-like particles attach in to the same bead-chain-like structure as observed with sol-gel synthesis method (described below), (10 — 15 nm diameter, 30 — 150 nm length). With the increase in the concentration of the template molecules (template molecule referred to herein is a heteroatom containing organic molecule such as an amine or an amide), directional growth of bead-like particles was controlled, resulting in a higher surface area in the nanostructures. Higher nanostructure surface area is preferred for more effective coating of plant nutrients and to increase the loading of nutrients onto the HAP.
A similar bead chain like structure was observed at lower urea encapsulation while the particles appeared to be more spherical in shape when the loading was increased. However even after a loading of 1:6 ratio of
HAP:Urea, the composite displayed particle sizes below 100 nm.
Example 2: a) Synthesis of HAP — Urea Nanocomposites by Sol-Gel Method
HsPO, (0.6 M, 250 ml) was added drop-wise into a suspension of calcium hydroxide (19.29 g Ca(OH), in 250 ml water), while stirring vigorously under mechanical agitation (1000 rpm). HAP-nanoparticle dispersion is created. The reaction takes place according to the following equation. 6 HPO, + 10 CaOH Ca p(PO4)s(OH), + 18 HO
HAP nanoparticle synthesis was repeated at different experimental conditions varying the following parameters: (iy Addition rate of reactants: direct addition of phosphoric acid to calcium hydroxide dispersion, phosphoric acid at 70 ml/min, phosphoric acid at 20 ml/min and phosphoric acid at 6 ml/min, (ii) pH: 5,7, 9 and 11 (iii) Addition method: spraying and drop wise addition (iv) Stirring speed: 100, 200, 300, 400, 600 and 800 rpm (v) Reaction temperature: 20 °C, 30 °C, 40 °C and 60 °C (vi) Concentration of phosphoric acid: conc. H;PO,4 (11 M) and 0.6 M
Surface modification of HAP nanoparticles with urea was carried out as described below. Urea solution (1 M, 250 ml) was added drop wise into the above-prepared HAP nanoparticle dispersion. In a preferred embodiment 25 g of solid urea is added to the HAP dispersion. Using solid urea reduces the amount of water in the mixture, improving the drying process. The resulting solution was allowed to age further for 2 hrs at room temperature to yield a stable dispersion, which can be used for foliar applications or encapsulated within a biodegradable coating. Afterwards, the dispersion was dried at 60 °C overnight by use of oven drying or flash drying. b) Morphology of HAP — Urea Nanocomposite: Sol-Gel Method
As can be seen with reference to the TEM image of Figure 3(a), rod-like
HAP nanoparticles are shown. These HAP nanoparticles were created by the
Sol-Gel method described in Example 2 above.
Figure 3(b) is a TEM image of HAP-urea nanocomposites. These HAP- urea nanocomposites were created by the Sol-Gel method described in Example
2 above.
Using the Sol-Gel method described in Example 2 above, bead-like nanoparticles (diameter 10 — 20 nm with uniform size) formed initially and quick directional growth leading to a bead-chain like structure (10 - 15 nm diameter, 30 —- 150 nm length) was observed.
C) Effect of Reaction Conditions (i — vi) (i) Effect of addition rate
Bead-like HAP nanoparticles with a diameter of approximately 10-35 nm were initially formed. Quick directional growth leading to bead-chain-like structures with 10 — 35 nm diameter and 150 nm length occurred with faster addition rates of phosphoric acid. Bead-chain-like morphology was observed for addition rate of 20 ml min”. Bead-chain-like morphology with a particle diameter of 10-60 nm, was observed for the slower rates 6 ml min. Bead-chain-like nanostructures were longer in length with the decrease in the addition rate of phosphoric acid suggesting that the longer time duration allows more efficient directional growth of bead-like nanoparticles. It is most preferable for the fertilizer application disclosed herein to use the addition rate of 70 ml min. (il) Effect of solution pH
As shown in Figure 8, bead-chain-like nanoparticle morphology was observed at all pH values of the final solution while a phase pure material was observed at all pH values studied. However, the particle diameter varied within a range of 10 — 100 nm. It was evidenced that the length of the bead-chain-like particles depends on the hydroxyl ion concentration in the solution. The length of the particles were longer when high concentrations of hydroxyl ions are used while the particle diameter does not significantly depend on hydroxyl ion concentrations. (iii) Effect of addition method
As can be seen in Figure 9, phase pure nanoparticles with a bead-chain- like morphology were observed for both the drop wise and spray methods of addition. Smaller particles (diameter 10-40 nm) with more uniform particle size distribution were observed for the more preferable spraying method. (iv) Effect of stirring speed
Synthesis of HAP nanoparticles was carried out under different stirring speeds (100, 200, 400, 600 and 800 rpm) in a semi pilot plant reactor. Phase pure bead-chain-like nanoparticles (diameter 10 — 60 nm, length 50 — 100 nm) were observed under all tested stirring speeds. Particle diameter (ca. 60 nm) was observed for the lowest rate speed (100 rpm) and small particles with an average diameter ranging from 10 — 20 nm were observed for the highest, and most preferred, stirring speed of 800 rpm. (v) Reaction temperature
As shown with reference to Figure 11, at lower temperatures, longer bead-chain-like structures (10 — 50 nm in diameter, 50 — 200 nm in length) were formed. With the increase in the reaction medium temperature more spherical particles were formed (10 — 50 nm in diameter) suggesting that higher temperatures are less favorable for directional growth. In a preferred embodiment, ambient temperature was used. (vi) Concentration of phosphoric acid
With reference to Figure 12, the size and morphology of the particles used with concentrated phosphoric acid was similar to the bead-chain-like nanoparticles (diameter 10 — 50 nm, 50 -200 nm length) observed with 0.6 M phosphoric acid. It is more preferable to use concentrated phosphoric acid.
PXRD Characterization
PXRD studies on the HA nanoparticles synthesized were in close agreement with the reported results in the powder diffraction file for HA in the
ICDD, (PDF No. 09-0432) with lattice parameters of a = 9.42 A and ¢ = 6.90 A based on a hexagonal unit cell. No characteristic peaks of impurities such as
Ca(OH), and Ca;(PO,), were observed suggesting the formation of phase pure
HA prepared according to example 2. Polycrystalline nature of both HAP nanoparticles and Urea-HAP nanoparticle were confirmed by the diffraction data obtained by electron diffraction methods. The crystallite size as calculated according to Schrerrs formula is about 18 nm which may possibly corresponding to the nanospheres and further suggest that the directional growth occurs along c-axis.
Elemental Analysis
Energy Dispersive X-ray (EDX) analysis confirmed the presence of Ca (17.24 %) and P (10.16 %) which is in agreement with the expected Ca: P ratio of 1.67. Kjeldhal analysis confirmed the presence of 22% + 3% nitrogen in the nanocomposite.
FTIR Characterization
The nature of the interactions between HA nanoparticles and urea molecules were studied by FTIR characterization. Specifically, the peak shifts in the FTIR spectrum of HA nanoparticles particularly broadening and to a lower wavenumber shift in the O-H stretching frequency predicts that the interactions have occurred through the O-H bond of the HA nanoparticles. Urea, the N-
H stretching frequency appeared as a doublet at 3430 cm™ and 3340 cm™ which in urea bonded to HA nanoparticles had led to a noticeable peak broadening.
Further, the change in the carbonyl stretching frequency of pure urea from 1682 cm” to 1669 cm™ in urea adsorbed HA nanoparticles indicated that, as is expected, the C=0 electron density was being affected by interaction between urea molecules and HA nanoparticles. This observation was lent further credence by a noticeable peak shift of the N-C-N stretching frequency (1460 cm ') of urea to a lower frequency in urea modified HA nanoparticles (1446 cm™).
Raman spectroscopy :
Raman spectroscopy analysis (as shown in Figure 18) clarifies the bonding environment of Urea-HAP nanoparticle composite, particularly in the fingerprint region. As evidenced by the Raman spectroscopic data there is a noticeable shift in the peak at 800 cm” in HA to 775 cm™ in Urea-HAP nanoparticle composite and in the peak around 825 cm™ in HA to 800 cm™ in
Urea-HAP nanoparticle composite. These peaks may possibly arise from any metal ligand interactions, and can thus be assigned to any change in the coordination environment of the Ca ions suggesting the possibility of the presence of metal — ligand type interactions in addition to hydroxyl — carbonyl weak hydrogen bonding environment in Urea-HAP nanoparticle composite.
This evidence may further suggest that the possibility of having coordination bonding between any positively charged Ca terminating face of HAP nanoparticles and amino groups of urea. These observations are in accord with the different types of bonding observed for bone (HAP nanoparticles) protein interactions. According to previous studies of bone — protein nanocomposites, there could be three different types of interactions between HAP nanoparticles and proteins, namely, (i) van Der Waals, (ii) coulombic and (iii) complex formation.
BET analysis
BET surface area, pore size and average pore volumes of HAP nanoparticles and U-HA nanocomposites are summarized in Table 1.
Table 1: BET surface area, pore size and pore volumes of the HAP nanoparticles and U-HA nanocomposites.
Single Point Adsorption
Total pore volume of at P/Po 0.96714194 (cm®/g)
As evidenced by the BET analysis in Table 1, the HAP nanoparticles synthesized as described in this study have a significantly high surface area compared to literature values. The directional growth of bead-like nanoparticles into a bead-chain-like nanostructure may have introduced the observed unique features. The number of layers of urea molecules around one HAP nanoparticles calculated referring to the BET was 53, suggesting the presence of a nanocomposite where HAP nanoparticles are surrounded by urea molecules which are H-bonded to each other in an extended fashion representing a poly urea molecule.
Release properties of nitrogen (a) In water
Method:
After adjusting the nitrogen content in each of the following samples to 20% of dry weight, they were used for evaluating the release of urea (N) in water: (1) Urea (2) Urea —HAP nanoparticles (powdered and in chip form) (3) Urea and HA (200 — 800 microns)
Urea adsorbed HAP-nanoparticles (5g, powder form), Urea adsorbed
HAP-nanoparticles (5 g, chips), Urea — HAP macroparticles (5 g, powder form), urea (2.15 g), all equalized to 20 % of nitrogen of dry weight were used for the study of the release behavior in water.
Each of above samples was placed in a vessel partitioned with a semi- permeable membrane. The samples were allowed to equilibrate with water (25 ml) in one side of the membrane and diffuse through the semi-permeable membrane to the other side; samples were withdrawn at 1 hr intervals. The samples were analyzed using FTIR and for the appearance of the urea peak in each sample: The peaks were normalized with respect to O-H stretching frequency peak of water which did not shift and area under the peak was analyzed for N-C-N stretching frequency peak of urea. Figure 19 summarizes the urea release behavior for these samples.
A similar procedure was followed to study the release behavior of aqueous solutions of HAP-Urea nanoparticle composites prepared with different
HAP: Urea ratios (1:1 — 1:6). Figure 20 summarizes the urea release behavior for these samples.
With reference to Figure 19, a rapid release of urea in aqueous medium was observed for urea and the composite prepared with hydroxyapatite macroparticles. 75% of the total urea used was released within the first 50 hrs while a clear slow and sustained release was observed for Urea-HAP nanoparticle chip and Urea-HAP nanoparticle powder. A steady state was reached after 50 hrs. The amount of urea released after 120 hrs for the U-HA chip was estimated to be 85% while 90% of urea was released within the same time duration for the Urea-HAP nanoparticle powder. Both the powder phase and chip-like nanocomposites released almost 95- 98% of urea added suggesting a more stable and uniform composite.
A similar release behavior in water was observed for the HAP —urea nanocomposite prepared by the template synthesis method.
With reference to Figure 20, HAP-Urea nanoparticle composite with a ratio of 1:1 displayed the slowest release behavior compared to the other formulations with higher urea loadings. However, a similar pattern in rate of release of urea was observed with all the other formulations with different urea loading. The presence of increased urea amounts may weaken the H-bonding interactions between the urea molecules and HAP nanoparticles. Furthermore, the rate of release of urea in solution phase composite was significantly slower than that of the Urea-HAP nanoparticle composite obtained as solid chips. (b) In acidic soil (pH 5.0)
Soil sample (400 g each of soil found at an elevation of 1600 feet in a tea plantation; pH 5.0) was mixed with 1.8 g of commercial urea fertilizer. The soil sample containing urea fertilizer was filled into a glass column. Similarly, three equal amounts of Urea-HAP nanoparticle composite (N — 15.5%) having a N content equal to urea, were taken separately and filled into three glass columns containing three soil samples (three replicates). Next, 180 ml water was added to all four soil columns until they reached the soil water saturation point, and maintained the water content approximately constant throughout the period of study. Water (100 ml) was added at five day intervals prior to elution. The eluted solutions (50 ml) were collected for nitrogen analysis. Nitrogen analysis was done by the Kjeldhal (N) method.
At soil pH 5, sustained release behavior of nitrogen was shown by the nanocomposite based on Urea-HAP nanoparticle and gradual release behavior can be clearly identified with the increasing of cumulative nitrogen content up to
80™ day in a slow manner, which is in agreement with a typical slow release profile presented by cumulative release vs. time in the literature. However, urea composition had released almost 50 % of N within 25 days and release of nitrogen had leveled off at 70 % after the 50™ day. Only 60% of the urea was released even after the 80" day and the results were highly reproducible.
Bio-availability Test — Using rice as the crop plant 1 — No fertilizer 2 — Urea as recommended by the Department of Agriculture — Sri Lanka 3-7 the amount of urea as recommended by the Department of Agriculture- Sri
Lanka 4 - % the amount of Urea- HAP nanoparticles composite containing N as recommended by the Department of Agriculture - Sri Lanka
Pot trials conducted at the Rice Research and Development Institute, Sri
Lanka, using rice as the model crop (see Figures 22-28) indicated an increase in the crop yield (grain weight/g per pot) using 50% N content (as compared to the recommended) was equal to or better than 100% N content in normal fertilizer.
Significantly, one basal treatment of the nanparticle composite was sufficient to meet the nitrogen demand of the plant during the total life span, compared with three bi-weekly applications in addition to the basal treatment when the conventional urea system (recommended by the Department of Agriculture, Sri
Lanka).
a ~~
COMPOSITION AND METHOD FOR SUSTAINED RELEASE OF © Fit be of.
AGRICULTURAL MACRONUTRIENTS 0
This invention relates to a composition for and a method of providing ‘sustained release of agricultural nutrients. More particularly this invention refates to nitrogen containing macronutrient adsorbed hydroxyapatite phosphate (HAP) nanoparticles and a method of using nitrogen containing macronutrient adsorbed hydroxyapatite phosphate nanoparticles as a slow-release fertilizer.
Commercial fertilizers contain macronutrients and micronutrients that are essential for plant growth and macronutrients are used by plants in relatively large amounts. As defined herein primary macronutrients are nitrogen (N), phosphorous (P) and potassium (K) while calcium (Ca), magnesium (Mg) and sulfur (S) are secondary macronutrients. All six nutrients are important for plant growth.
As defined herein, micronutrients required in small amounts for plant growth are boron (B), chlorine (Cl), manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), molybdenum (Mo) and selenium (Se).
Nitrogen, phosphorus and potassium (NPK), which are required in large amounts for plants, are not always adequately available in natural soils to support the sustained growth of plants. Therefore, these macronutrients (NPK) are often needed to be applied externally through fertilizer. Water soluble i conventional fertilizers typically result in a large amount of macronutrients being lost by leaching and evaporation. Thus, there is an increased interest in developing slow release fertilizers that release macronutrients to plants over time.
Advantages of slow release fertilizers are improved efficiency and quality as the fertilizer is released over time, thus providing sufficient quantities of macronutrients as required for higher crop yields. In addition, slow release fertilizers result in reduced environmental damage from leaching of macronutrients into water and emissions as gasses, compared to conventional water soluble fertilizers.
Macronutrients in fertilizers can be applied to the soil as a solid in the form of a powder or pellets or as a spray. The uptake of macronutrients by the plant needs to be compensated by their external application to the soil periodically. Nitrogen is a key macronutrient source in agriculture particularly for economic crops such as tea. For example, large amount of fertilizer is applied to the soil of the tea plant to improve the quality and the yield of the leaves produced. A study in Japan (Yamada et al., Journal of Water and Environmental
Technology, 7, 4, 331-340, 2009) reported that of the large amount of nitrogen fertilizer applied to tea, only 12 % of the nitrogen input was taken up by the plant and the rest discharged to the environment. Therefore, one of the unsolved problems of fertilizer application is, in relation to the amounts of nitrogen applied to soil, the low Nitrogen Use Efficiency (NUE) by crops. This is because an excessive amount of nitrogen, up to 70 %, is lost when using conventional fertilizers due to leaching, emissions and long-term incorporation by soil microorganisms. As such, supplying nitrogen macronutrient is critical in preventing the decline of productivity and profitability due to degradation and aging of tea plants (Kamau et al., Field Crops Research 1, 108, 60-70, 2008).
Attempts to increase the NUE have so far has met with little success.
US 6,261,997 B1 to Rubin et al. discloses slow release of pesticides adsorbed on organically modified clay to prevent leaching in underground and surface water. US 4,219,349 to Bardsley discloses compositions of calcined clay granules and solution or suspension containing micronutrients (Fe, Zn, Mn, Cu,
B, Mo, Cl and S). US 4,849,006 to Milburn et al. discloses a controlled release composition comprising of an organic, biologically active material absorbed on an organically modified clay. US 6,821,928 B2 to Ruskin discloses a method to reduce the rate of diffusion of slow release materials through polymers and a process for making drip irrigation devices with long term control of root growth. it further, discloses bioactive material such as herbicide that is intercalated into nanoclays to protect against root intrusion in drip irrigation applications. US 3,902,886 to Banin et al. discloses clay attached micronutrients to provide micronutrients to plants. US2009/0169524 A1 to Kalpana et al. discloses biopolymer based nanocomposites of chitosan, montmorillonite (MMT) and hydroxyapatite for bone growth in medical applications.
Solutions are needed to provide slow release macronutrient formulations for plant growth applications.
A nitrogen containing macronutrient is adsorbed on HAP nanoparticles and used as a fertilizer. The macronutrient adsorbed HAP nanoparticles disclosed herein, when applied to aqueous and terrestrial environments, slowly release the macronutrient to the soil. The soil medium acts as a conduit for providing the transport of the macronutrients such as urea to the roots of the plant.
Figure 1: SEM images of an embodiment of the present invention showing the urea adsorbed HAP nanoparticles prepared by template method (a) as synthesized and (b) after 2 hrs of synthesis, resulting as a solid chip, showing nanobeads and bead-chain-like structures obtained by the directional growth of nanobeads, respectively.
Figure 2: SEM images of an embodiment of the present invention where showing the urea adsorbed HAP nanoparticles foliage formulations prepared with HAP:Urea (a) 1:1, (b) 1:3, (c) 1:4, (d) 1:5 and (e) 1:6.
Figure 3: TEM images of an embodiment of the present invention showing (a) synthesized HAP nanoparticles and (b) urea adsorbed HAP nanoparticles.
Figure 4: SEM image of an embodiment of the present invention showing the bead-chain-like structure of the HAP-urea nanoparticles formed by the Sol-
Gel method.
Figure 5: Crystallographic representation of HAP nanoparticles.
Figure 6: Schematic representation of the directional growth of nanobead like nanoparticles into bead-chain-like particles.
Figure 7: SEM images of HAP nanoparticles formed with different addition rates of phosphoric acid, (a) 250 ml min™*, (b) 70 ml min”, (¢) 20 ml min™ and (d) 6 ml min”.
Figure 8: SEM images of HAP nanoparticles formed at different pH values (a) 5, (b) 7, (c) 9 and (d) 11.
Figure 9: SEM images of HAP nanoparticles prepared by (a) drop wise addition and (b) spray addition methods.
Figure 10: SEM images of HAP nanoparticles prepared with different stirring speeds, (a) 100, (b) 200, (c) 300, (d) 400, (e) 600 and (f) 800 rpm.
Figure 11: SEM images of HAP nanoparticles prepared at different reaction temperatures (a) 10 °C, (b) 25 °C, (c) 70 °C, (d) 85 °C and (e) 100 °C.
Figure 12: SEM images of the HAP nanoparticles prepared using (a) 0.6
M and (b) conc. phosphoric acid.
Figure 13: PXRD patterns for Urea, an embodiment of the present Urea-
HAP nanoparticle composite invention and HAP nanoparticles.
Figure 14: Electron diffraction patterns of (a) HAP nanoparticles and (b) an embodiment of the present Urea-HAP nanoparticle composite invention.
Figure 15. FTIR spectra for the carbonyl stretching region of (a) HAP nanoparticles (b) an embodiment of the present Urea-HAP nanoparticle composite invention and (c) Urea.
Figure 16: FTIR spectra for the amine stretching region of (a) HAP nanoparticles (b) an embodiment of the present Urea-HAP nanoparticle composite invention and (c) Urea.
Figure 17: FTIR spectra for the N-C-N stretching region of (a) HAP nanoparticles (b) an embodiment of the present Urea-HAP nanoparticle composite invention and (c) Urea.
Figure 18: Raman spectra of (a) Urea, (b) HAP nanoparticles and (c) an embodiment of the Urea-HAP nanocomposite of the present invention.
Figure 19: Release behavior comparison for Urea, Urea-HAP nanoparticle chip, Urea-HAP nanoparticle powder and Urea and HAP macroparticles in water.
Figure 20. Release behavior comparison in water for (a) Urea; embodiment of the present Urea-HAP nanoparticle composite invention with
HAP :Urea (b) 1:1, (c) 1:3, (d) 1:4, (e) 1:5 and (f) 1:6 in liquid phase.
Figure 21: Release behavior comparison for Urea and embodiments of a4 the present Urea-HAP nanoparticle chip invention, in soil.
Figure 22: Rice plant height/cm vs. treatments 1-4.
Figure 23: Number of tillers per pot vs. treatments 1-4.
Figure 24. Number of days to flower vs. treatments 1-4.
Figure 25: Number of panicles per pot vs. treatments 1-4.
Figure 26: 1000 grain weight/g vs. treatments 1-4.
Figure 27: Number of filled grains per pot vs. treatments 1-4.
Figure 28: Grain weight/g per pot vs. treatments 1-4.
As defined herein, slow release of macronutrients provides the plant with nutrients gradually over an extended period of time. As described herein in further detail, such an extended period of time can be up to three months. Soils applied with slow release fertilizer that contain macronutrients will require fewer applications of such fertilizer. Use of a slow release fertilizer leads to higher efficiency of macronutrient release compared to conventional fast release fertilizers.
Adsorption, as defined herein, refers to any means that forms a complex between the nitrogen containing macronutrient compound and the hydroxyapatite phosphate (“HAP” or “HA”) nanoparticles. These include covalent bonds, electrostatic bonds, Van der Waals bonds and hydrogen bonds.
Any other nitrogen containing substance which can deliver nitrate or nitrite to the plant can be used as the macronutrient for adsorption onto the HAP nanoparticles. Examples of such nitrogen containing substances include, but are not limited to, urea, thiourea, amides, polyamines, ammonia and alginates.
Overview of Manufacture and Morphology of HAP Nanoparticle — Nitrogen
Containing Macronutrient Composite
HAP nanoparticles can be chemically synthesized using calcium hydroxide suspension and phosphoric acid (Mateus et al., Key Engineering
Materials, 330-332, 243-246, 2007). A more detailed description of the synthesis of HAP nanoparticles is described herein.
Structural morphology of the HAP-nanoparticles described herein indicates an initial formation of bead-like HAP nanoparticles that grow into a bead-chain-like structures. This growth pattern suggests that one face of the bead-like HAP nanoparticle is possibly crystallized with a hexagonal unit cell and is highly energetic thus leading to a directional growth along one orientation. This directional growth may occur through the PO,> terminating plane. (See Figures 5 and 6). This results in a nanobead-chain-like structure leading to rod-like morphology. The directional growth is interrupted or delayed in the presence of spacer molecules such as amines and amides in the medium because Ca? may complex with the nitrogen donor.
Methods for adsorption of nitrogen containing macronutrient compounds such as urea on the HAP nanoparticles are also described herein.
SEM imaging indictes particle size of less than 30 nm for a preferred embodiment of macronutrient adsorbed HAP nanoparticles. According to TEM imaging (see Figures 3a and 3b) a preferred embodiment of macronutrient adsorbed HAP nanoparticles displays rod-like morphology similar to the HAP nanoparticles prior to adsorption. FTIR and Raman indicate that, in a preferred embodiment of these nanoparticles, urea is attached to the hydroxyl terminating and Ca®* terminating faces of the HAP nanoparticles.
According to the methods described herein, prior to drying, HAP-nitrogen containing macronutrient nanoparticles can be obtained as a stable aqueous dispersion. After drying, the HAP-nitrogen containing macronutrient nanoparticles can be obtained as a white solid chips or granules. Furthermore, these chips or granules can be ground to provide a powder. This grinding preferably takes place using a roll mill or a ball mill. The aqueous dispersions, chips or granules can be used as slow release macronutrient formulations.
Release behavior in soils
The macronutrient-adsorbed HAP nanoparticles disclosed herein can be used for supplying macronutrients for crops such as tea; rubber; coconut;
soybeans; cotton; tobacco; sugar cane; cereals such as rice, corn (maize), wheat, sorghum and wheat; fruits such as apples, oranges, tomatoes; vegetables; ornamental plants; and other short term cash crops that grow in a range of pH soils. Nitrogen-containing fertilizer is needed because production of crops removes nitrogen, which is essential for plant growth, from the soil. For example, the production of 1000 kg of tea leaves (dry weight) removes up to 100 kg of nitrogen from soil. This nitrogen has to be replenished by external application of fertilizer.
The nitrogen containing macronutrient adsorbed HAP nanoparticle composition described herein can be applied to the soil in the form of a powder, pellets, chips, a spray, or as an aqueous dispersion encapsulated within a biodegradable coating. In certain embodiments of the present invention, a slow release of nitrogen over a period up to three months is observed. During the fertilizing of tea plants, for example, the frequency of application can be attenuated depending on the fertilizer requirement of a given tea plantation. This can be done by starting a second round of application at a suitable period prior to reaching the end of the viability of the first application of the macronutrient adsorbed HAP nanoparticles. In another embodiment, multiple applications of the macronutrient-adsorbed HAP nanoparticles are distributed on soils within three months.
As a person skilled in the art may recognize, soil pH plays a role in the release behavior of the macronutrients from the macronutrient-adsorbed HAP nanoparticles to the soil. Further, soil pH is important in the growth of economic plants (Rice, Tea and Rubber) and ornamental plants (Ferns and Orchids).
Generally, tea plants thrive in acidic soils in the pH range between about 4.2 to 5.7. However, rice is more tolerant of slightly higher pH the ideal range being between about 5.0 — 6.0. It is believed that high organic matter content in soil could lead to lowering of pH of the soil. Elevation may play a role in the effect. In general, higher elevations contain more organic matter compared to lower elevations such as sea level. Organic matter content of soil between 1600 to 4000 feet elevation can range from 2 to 3%.
It is believed that, while not bound by theory, protonation of the macronutrient adsorbed HAP nanoparticles leads to the release of the adsorbed macronutrient. Here, urea, due to its basicity, can be readily protonated. This may aid the release process.
In an embodiment of the slow release method, soil having a pH of 5 found at about 1600 feet from tea plantations in Kandy, Sri Lanka, can be used with macronutrient adsorbed HAP nanoparticles to release the macronutrient in a slow and sustained manner. In another embodiment, pot trials carried out with rice at the Rice Research and Development Institute, Sri Lanka (pH 5.5 — 6.0) can be used with macronutrient adsorbed HAP nanoparticles to slowly release the macronutrient. Even in sandy soils found at sea level (pH 7), for example in
Colombo, Sri Lanka, where the organic content is lower than 2%, the slow and sustained release may be achieved. To summarize, while slow release of macronutrient compound will occur in soils having a pH range of 3.5 to 7.00, soils having acidic pH values in the range between about 4.2- 6.5 are most preferred.
Release behavior through foliage
In another embodiment, the aqueous dispersion obtained directly after the synthesis of the HAP-nitrogen containing macronutrient nanoparticles can be used to slowly release the macronutrient in foliar applications. Since leaf surface chemistry generally has a pH range between 5 and 7, such an aqueous formulation can release macronutrient as a foliar application in a local setting through manual application or on a wider scale by aerial spraying. These applications can be made multiple times during the life cycle of a plant as necessary.
Example 1: Template Synthesis Method a) Synthesis of HAP — Urea Nanocomposites by Template Synthesis
Method
Ca(OH)2 solution (19.29 g, 250 ml) was prepared and stirred for half an hour. Urea (31.28 g) was added to the solution and stirred further for one hour.
Claims (19)
1. A method of slowly releasing macronutrient to a plant locus a. providing a nanocomposite having nitrogen containing macronutrient compound adsorbed on the surface of hydroxyapatite phosphate nanoparticles and b. applying said nanocomposite to soil.
2. The method of claim 1 further comprising contacting the nanocompgsite with the soil more than once within a period of three months.
3. The method of claim 1 wherein the nanocomposite is aqueously dispersed.
4. The method of claim 3 further comprising contacting the nanocomposite with the foliar parts of a plant.
5. The method of claim 4 further comprising contacting the nanocomposite with the foliar parts of a plant more than once within a period of three months.
6. The method of claim 1 wherein the plant locus comprises a tea plant locus.
7. The method of claim 1 wherein the plant locus comprises a rice plant locus.
8. The method of claim 1 wherein the plant locus comprises a rubber plant locus.
9. The method of claim 1 wherein the plant locus comprises a coconut plant locus.
10. The method of claim 1 wherein the plant locus comprise a corn (maize) plant locus.
11. The method of claim 1 wherein the plant locus comprises a short term cash crops.
12. The method of claim 1 wherein the soil has a pH range between 4.2 to
6.5.
13. A method of preparing a sustained release fertilizer composition comprising:
a. preparing an aqueous Ca(OH), and nitrogen containing macronutrient dispersion;
b. adding phosphoric acid to the aqueous Ca(OH), and nitrogen containing macronutrient dispersion.
14. The method of claim 13 wherein the nitrogen containing macronutrient is urea.
15. The method of claim 14 wherein the aqueous dispersion is dried.
16. The method of claim 14 where the ratio of urea to hydroxyapatite phosphate is between (w/w) 1:1 to 1:6.
17. The method of claim 15 wherein the ratio of urea to hydroxyapatite phosphate is about (w/w) 1:1.
18. A fertilizer composition comprising a nitrogen containing macronutrient adsorbed on the surface of hydroxyapatite phosphate nanoparticles.
19. The fertilizer composition of claim 18 wherein the fertilizer composition is a solid; wherein the nitrogen containing macronutrient is urea; and wherein the ratio of urea to hydroxyapatite phosphate is about (w/w) 1:1.
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