Encapsulated nano-ionic diammonium phosphate (DAP) fertilizer using a digested protein-sugar biopolymer matrix

Abstract

An encapsulated fertilizer composition comprising nano-ionic diammonium phosphate particles as a nutrient core, the nutrient core being completely surrounded by a digested protein-sugar biopolymer matrix forming a continuous encapsulation shell that is biodegradable, moisture-reactive and designed to enable controlled release of ammonium and phosphate ions to plants.

Description

AREA OF INVENTION:

[0001] The invention relates to the field of advanced agricultural fertilizers, in particular controlled-release nano-fertilizers. It concerns the design and formulation of nano-ionic diammonium phosphate (DAP) encapsulated in a digested protein-sugar matrix, functioning as a biodegradable, nutrient-regulating biopolymer. The invention is situated within the fields of nano-agriculture, intelligent nutrient delivery systems, and sustainable crop management inputs. BACKGROUND OF THE INVENTION:

[0002] Conventional diammonium phosphate (DAP) fertilizers have been widely used in global agricultural systems due to their balanced ammonium and phosphate content. However, the agronomic efficiency of DAP remains significantly limited by its rapid solubility, high leaching potential, evaporation losses, and fixation phenomena in various soil types. A substantial portion of the phosphate is immobilized through reactions with calcium, iron, and aluminum compounds, while ammonium nitrogen frequently undergoes conversion losses through nitrification and denitrification. Consequently, typical nutrient utilization efficiency remains below 40%, leading to excessive fertilizer use, economic burden on farmers, and environmental degradation through groundwater pollution and eutrophication.

[0003] Recent advances in nanotechnology have spurred the development of nanoscale nutrient particles with improved soil mobility and targeted plant uptake. However, uncoated nano-DAP formulations face additional challenges, including aggregation, rapid dissolution, lack of release control, and instability under varying pH and moisture conditions. Similarly, existing controlled-release fertilizers largely utilize synthetic polymers, which exhibit limited biodegradability, contribute to microplastic accumulation, and do not provide ionic stabilization of the nutrient particles.

[0004] Biopolymer-based encapsulation systems offer promising solutions, but most existing matrices are based on expensive protein isolates or chemically modified polysaccharides, limiting their widespread agricultural use. Digested protein-sugar complexes derived from natural, low-cost biological sources offer a unique alternative, exhibiting superior biodegradability, chelation capacity, moisture-reactive permeability, and film-forming properties. However, no prior art demonstrates a nano-ionic DAP encapsulated in a digested protein-sugar matrix that exhibits ionic stability, controlled nutrient diffusion, and improved agronomic performance.

[0005] Therefore, there is a clear need for a novel, stable, biodegradable, environmentally friendly, encapsulated nano-ionic DAP product that is able to overcome the limitations of conventional fertilizers while supporting sustainable agriculture. SUMMARY OF THE INVENTION:

[0006] The invention introduces a biopolymer-coated nano-ionic DAP fertilizer composition designed to improve nutrient release efficiency and minimize environmental losses. The core of the invention is a population of nanoscale DAP particles in ionic form, dispersed and uniformly coated within a digested protein-sugar matrix. The coating material possesses amphiphilic, adhesive, and reactive functional groups that bind to ammonium and phosphate ions, stabilizing them against premature dissolution and soil fixation.

[0007] The digested protein-sugar matrix forms a continuous nanoscale shell around each DAP particle. This shell acts as a semipermeable barrier capable of regulating nutrient diffusion in response to soil moisture, root exudates, and microbial interactions. The biopolymeric structure comprises naturally occurring peptides, amino acids, and reducing sugars that participate in hydrogen bonding, ionic bridges, and the formation of inclusion complexes. This matrix gradually decomposes in the soil, releasing nutrients in a synchronized manner that meets the physiological needs of plants.

[0008] The invention provides a fertilizer composition characterized by an increased surface area, high dispersion stability, improved bioavailability of phosphate ions, reduced fixation, and prolonged persistence in the soil. The product is particularly suitable for crops requiring sustained nutrient availability or grown under conditions prone to nutrient losses. The encapsulated nano-ionic DAP also promotes beneficial microbial activity, improves root development, and reduces the frequency of fertilizer application. DETAILED DESCRIPTION OF THE INVENTION:

[0009] The invention relates to a novel fertilizer composition in which nano-ionic diammonium phosphate is encapsulated in a digested protein-sugar biopolymer matrix, creating a unique nutrient release system designed to improve the agronomic efficiency, stability, and controlled nutrient release properties of one of the most widely used agricultural fertilizers. The composition represents a significant advance in nano-fertilizer technology by combining the advantages of reduced particle size, ionic dispersion, and bio-based polymer encapsulation, thereby overcoming the inefficiencies of conventional DAP and addressing long-standing problems such as nutrient waste, soil fixation, environmental losses, and low nutrient utilization efficiency.

[0010] Central to the invention is the creation of a nano-ionic DAP structure in which ammonium and phosphate ions remain in a highly dispersed, nanoscale particle form, exhibiting a significantly increased surface area. This nanoscale dispersion enables more effective interaction with the soil microenvironment and plant root systems. Traditional DAP tends to dissolve and become fixed rapidly upon contact with mineral components of the soil, particularly calcium in calcareous soils or iron and aluminum in acidic soils. These interactions form insoluble phosphate complexes that are no longer accessible to plants, resulting in exceptionally low utilization rates.The invention addresses this challenge by encapsulating each nano-ionic DAP particle in a continuous, uniform shell of digested protein-sugar matrix, which acts as a semi-permeable, protective and bioactive barrier.

[0011] The digested protein-sugar matrix used in this invention is a biodegradable, natural biopolymer system consisting of peptides, amino acids, reducing sugars, partially hydrolyzed polysaccharides, and Maillard reaction products generated by controlled biological or enzymatic digestion of protein-carbohydrate complexes. These components exhibit exceptional physicochemical properties, including ionic compatibility, hydrophilicity, film-forming ability, and adhesive interaction with inorganic nutrient ions. The biopolymer matrix inherently contains functional groups such as amino, carboxyl, hydroxyl, imine, and carbonyl residues, which enable strong interaction with ammonium and phosphate ions.These interactions occur through hydrogen bonds, ionic pairing, in some cases covalent stabilization and polymer interweaving mechanisms, enabling the matrix to encapsulate the nano-ionic DAP core in a stable and homogeneous manner.

[0012] Once the nano-ionic DAP particles are coated with the digested protein-sugar matrix, the resulting composition forms stable micro-nano composite structures that protect the nutrient core from immediate dissolution. The encapsulation layer is typically 5 to 30 nanometers thick and provides an effective balance between structural integrity and controlled permeability. Under dry conditions, the shell remains compact, preventing nutrient loss. Upon contact with soil moisture or irrigation water, the matrix absorbs water and gradually swells, enabling the controlled and sustained release of ammonium and phosphate ions. This moisture-responsive permeability property ensures that nutrient release more closely matches the physiological uptake behavior of plants, minimizing nutrient waste, leaching, and evaporation.

[0013] The invention further introduces a composition in which the nano-ionic DAP maintains colloidal stability, prevents aggregation, and ensures uniform dispersion in the soil or hydroponic system. The biopolymer matrix provides steric and electrostatic stabilization by forming a hydrated shell around each nutrient particle, thus ensuring that the nano-ionic particles do not form clusters or precipitates. This improves mobility within the microporous structure of the soil and facilitates interaction with root hairs and rhizosphere microbes, leading to enhanced penetration and assimilation. Furthermore, the naturally occurring components of the biopolymer support microbial proliferation, which in turn contributes to matrix degradation and nutrient release at the appropriate stages of plant development.

[0014] In many soils, phosphate ions tend to become immobilized due to reactions with metal ions or adsorption onto clay surfaces. The encapsulated nano-ionic DAP composition significantly reduces these immobilization tendencies. The digested protein-sugar matrix holds the phosphate ions in a nano-ionic form, thus keeping them spatially separated from reactive soil components and maintaining them in a highly available state for root uptake. Simultaneously, the ammonium ions in the DAP core are protected from immediate volatilization or rapid nitrification, minimizing nitrogen losses. This dual protection of nitrogen and phosphorus increases nutrient utilization efficiency and reduces the overall amount of fertilizer required to achieve optimal yields.

[0015] The invention also demonstrates a synergistic interaction between the biopolymer matrix and the soil microflora. The peptides, amino acids, and sugar derivatives contained in the biopolymer serve as substrates for beneficial soil microbes and promote the growth of the microbial population in the rhizosphere. The enzymes produced by the microbes, which are part of normal soil metabolism, gradually degrade the encapsulation layer, resulting in a gradual release of nutrients in line with plant needs. This mutual interaction contributes to sustainable nutrient management and supports ecological resilience in agricultural areas. In addition, the degradation products of the biopolymer matrix enrich the organic matter content of the soil and improve the soil's water retention capacity, leading to long-term benefits for soil health.

[0016] The structure of the encapsulated nano-ionic DAP particles in the invention is characterized by its uniformity and controlled physicochemical properties. The nano-ionic DAP core generally has a particle size of 10 to 80 nanometers, ensuring high reactivity and surface contact. The digested protein-sugar shell completely encloses the core, creating a smooth and continuous coating. The interaction between the core and the shell is non-mechanical and arises from molecular bonds and the self-assembly of biopolymers. These properties allow the composition to remain stable during storage, transport, and application without significant degradation or clumping.

[0017] When applied to the soil, the encapsulated nano-ionic DAP particles disperse more evenly due to their small size and hydrophilic coating. As water begins to penetrate the biopolymer matrix, the encapsulated layer slowly swells, initiating a diffusion-controlled release process. The first phase involves the hydration of the outer surface, followed by the gradual penetration of water molecules to the nutrient core. Release rates depend on environmental conditions such as moisture level, temperature, soil pH, and microbial density. This release mechanism differs significantly from conventional fertilizers, which dissolve almost instantly upon contact with water, resulting in a rapid increase in nutrients that exceeds plant uptake.

[0018] The invention enables a more controlled, gradual, predictable, and crop-responsible nutrient release scheme. In field conditions, this translates to extended nutrient availability, reduced need for frequent fertilizer applications, and a minimized risk of nutrient burn. The nano-ionic nature of the nutrients ensures improved uptake efficiency, as plant roots preferentially absorb nano-sized ions due to their higher mobility and compatibility with root transport membrane systems. Phosphate ions, which otherwise move poorly in the soil due to their low mobility, achieve improved reach in the root zones because the nano-ionically encapsulated system prevents precipitation and immobilization.

[0019] The encapsulated nano-ionic DAP composition described in this invention also exhibits compatibility with multiple application modes, including direct soil application, fertigation, saturation coating, foliar spraying, and integration with other nutrient systems. The hydrophilic nature of the biopolymer matrix enables rapid dispersibility in water, making it suitable for modern precision agriculture practices. Furthermore, the composition can be mixed or co-formulated with micronutrients, beneficial microbes, organic fertilizers, and soil amendments without undergoing undesirable chemical interactions.

[0020] Another significant advantage of the invention is its contribution to environmental sustainability. Traditional fertilizers are major contributors to nitrate contamination of groundwater, eutrophication of water bodies, and soil acidification. The controlled release of the encapsulated nano-ionic DAP reduces the nutrient loss rate and thus mitigates these environmental impacts. The biopolymer matrix is ​​completely biodegradable and decomposes into environmentally friendly byproducts, unlike synthetic polymer coatings, which are commonly used in slow-release fertilizers and contribute to microplastic accumulation in soil systems.

[0021] The invention also offers stability advantages during storage. The digested protein-sugar matrix individually encapsulates each nano-ionic particle, preventing moisture absorption, clumping, and nutrient degradation during extended storage periods. The capsule layer provides physical stability, chemical stabilization, and protection against environmental influences such as humidity and temperature fluctuations. Thus, the product retains its efficacy from production to use without significant loss of functional properties.

[0022] When interacting with plant systems, the nano-ionic DAP composition exhibits improved bioavailability due to its nanoscale structure and bio-interactive shell. The digested protein-sugar components act as signaling molecules, attracting root exudates and stimulating active nutrient uptake. The biopolymer can also modulate the pH microgradients of the rhizosphere, enabling improved phosphate solubility and uptake even under challenging soil conditions. When released, the ammonium ions support root growth, chlorophyll synthesis, and early vegetative development, while the phosphate ions contribute to energy transfer, root development, and flower and seed formation. Thus, the invention synchronizes nutrient release with the plant's physiological stages.

[0023] The encapsulated nano-ionic DAP of this invention is structurally stable, functionally innovative and agronomically superior to existing fertilizer formulations.

[0024] Its unique properties result from the harmonious interaction between nano-ionic nutrient cores and the digested protein-sugar encapsulation system, which ensures optimal nutrient release, environmental protection, soil regeneration, and increased yield. The invention relates to the composition and structure of the nano-ionically encapsulated fertilizer product, independent of a specific manufacturing method, and represents a novel advancement in sustainable agricultural nutrient technology.

Claims

[1] An encapsulated fertilizer composition comprising nano-ionic diammonium phosphate particles as a nutrient core, wherein the nutrient core is fully surrounded by a digested protein-sugar biopolymer matrix forming a continuous encapsulation shell that is biodegradable, moisture-reactive and designed to enable controlled release of ammonium and phosphate ions to plants. [2] Fertilizer composition according to claim 1, wherein the nano-ionic diammonium phosphate particles have a primary particle size of 10 nm to 80 nm and remain in a colloidally stable dispersed form within the encapsulation shell. [3] Fertilizer composition according to claim 1, wherein the digested protein-sugar biopolymer matrix comprises peptides, amino acids, reducing sugars, hydrolyzed polysaccharides and Maillard reaction products with amino, carboxyl, hydroxyl and carbonyl functional groups which combine with the nutrient core to form a stable encapsulated structure. [4] Fertilizer composition according to claim 1, wherein the encapsulation layer has a thickness of 5 nm to 30 nm and is configured to gradually swell upon exposure to moisture in order to enable diffusion-controlled nutrient release. [5] Fertilizer composition according to claim 1, wherein the encapsulated nano-ionic diammonium phosphate particles exhibit reduced phosphate fixation in the soil, reduced volatilization of ammonium ions and improved nutrient utilization efficiency compared to conventional diammonium phosphate. [6] Fertilizer composition according to claim 1, wherein the biopolymer matrix increases microbial activity in the rhizosphere, facilitates microbially induced decomposition of the capsule shell and improves nutrient availability by synchronized release with the physiological needs of the plant.