Compositions for delivery of boron to plants and methods of preparing same

Abstract

The present disclosure provides compositions including a carrier, an element and boron. The carrier is a network of polymers including cellulose and / or starch, the element is bonded to hydroxyl groups of the polymers of the carrier, and boron is bonded directly or indirectly to the carrier. When boron is bonded directly to the carrier, boron is bonded to hydroxyl groups of the carrier. When boron is bonded indirectly to the carrier, boron is bonded to the element. The compositions are added to soil for delivery of boron to plants. Also provided are methods of preparing such compositions.

Description

COMPOSITIONS FOR DELIVERY OF BORON TO PLANTS AND METHODS OF PREPARING SAMEFIELD

[0001] This invention relates to compositions and methods for delivery of boron to plants, and methods for preparing such compositions. In particular, the invention relates to compositions including a carrier comprising cellulose and / or starch, an element and boron, the boron being bonded directly or indirectly to the carrier.BACKGROUND

[0002] In modern agriculture, nutrients are applied to soils to maximize the growth of plants. However, a significant proportion of nutrients simply wash away from the soils because they are water soluble. For example, rain and irrigation may cause applied nutrients to move vertically through the soil and away from plant roots, thereby limiting or prohibiting nutrient uptake by plants. Another issue with nutrient solubility in soils is agricultural run-off, which is a major contributor to the eutrophication of fresh water bodies.

[0003] Trace metals, such as iron, zinc, copper, boron and magnesium, are also important components of soil chemistry that may be depleted by environmental effects and crop uptake, resulting in decreased crop yields. Trace mineral depletion may be caused by nitrogen, phosphorous, potassium (NPK) fertilizers, which are known to dilute the concentrations of other nutrients in plants. Although NPK fertilizers improve crop yields, their use combined with progressively higher-yielding crop varieties may produce foods with lower mineral and nutrient concentrations than their less productive ancestors (Henkel M. Sustainable Agriculture III: Agricultural Practices. 2005; 18-19).

[0004] Boron is an essential micronutrient often considered one of the most widespread crop nutrient deficiencies worldwide. It plays a crucial role in normal plant growth and development by maintaining structure and function to the plant cell wall among other critical mechanisms. Under normal conditions, boron is taken up by plants via the root system as boric acid (H3BO3) which has very low retention in soil. However, many issues arise from the use of boron fertilizers, and the high solubility of boron compounds in water. Leaching readily occurs especially in areas of high humidity andcoarse textured soil, leading to poor fertilizer efficiency and agricultural run-off that contributes to eutrophication of fresh water sources. Boron toxicity also presents an issue if application rates are too high. The range between micronutrient toxicity / deficiency is exceptionally narrow for boron. Sodium borates (for example, borax) are frequently employed as a primary source of B fertilizer, but their pronounced solubility elevates the potential for seedling toxicity and high nutrient leaching later in the growing season.

[0005] To circumvent current issues, slow-release fertilizers have been employed which release nutrients at a more gradual pace, prolonging nutrient accessibility to the plant. Ideally, the release rate of a slow-release source should strike a balance. It should be slow enough to mitigate excessive leaching and seedling toxicity, while still delivering nutrients within a reasonable timeframe for optimal crop growth. Many slow- release boron fertilizers have been developed. These include crushed borate ores of sparing solubility such as colamite and ulexite, BPO4 produced from boric acid and phosphoric acid, and physical / chemical incorporation of borax into slow-release material matrices. However, these fertilizers require energy intensive thermal processes for synthesis, and as a result, the cost of these products are prohibitively expensive.

[0006] In solution, boron exists in an equilibrium between boric acid and the borate anion with the pKa of this acid / conjugate base pair at 9.2. Thus, at pH levels below 9.2, equilibrium favors the formation of boric acid while above this pH, the borate anion dominates. It is well documented that borate reacts with diols and polysaccharides forming boroesters. Scheme 1 (A) illustrates this, where the condensation reaction of a diol unit with borate yields a boroester. This complex may react once more with an additional diol unit to form a second boroester moiety (Scheme 1 (B)).cross-linked diolsScheme 1

[0007] Thus, borate anions may serve as cross-linking agents for diols under appropriate conditions. Diol stereochemistry is an important factor in the degree of cross-linking interactions formed, with cis vicinal diols presenting the optimal configuration for borate complexation. Cellulose is a polysaccharide consisting of a linear chain of [3(1 ,4) linked glucose units. Previous studies have shown that equatorial hydroxide groups on the pyranose ring are open to cross-linking interactions with borate under alkaline conditions. These cellulose-borate interactions have been leveraged to engineer wood composites, fire-retardant materials, and hydrogels. However, due to the hydroxide stereochemistry within the cellulose backbone (ie. lack of cis diols), the degree of cross-linking interactions is low relative to the formation of singular boroester units.

[0008] Thus, there remains a need for a material that retains boron in a bioavailable form to plants and provides sufficient boron to plants to act as a fertilizer, but does not leach toxic amounts of boron into the environment.SUMMARY

[0009] In one aspect, the present disclosure provides compositions for use in delivering boron to a plant, the compositions including a carrier comprising cellulose and / or starch, an element and boron. The boron-containing compositions as described herein have reduced solubility in water compared to other boron-containing compoundsand compositions, while still providing the boron to plants in bioavailable form. Also provided are methods of making such compositions.

[0010] Various aspects of the present disclosure provide a composition comprising: a carrier comprising cellulose and / or starch, wherein the carrier is a network of polymers; an element bonded to hydroxyl groups of the polymers of the carrier; and boron bonded directly and indirectly to the carrier, wherein boron bonded directly to the carrier comprises bonding of boron to hydroxyl groups of the carrier and boron bonded indirectly to the carrier comprises bonding of boron to the element.

[0011] In various embodiments, the boron is a crosslinking agent between polymers of the carrier, wherein the crosslinking is between hydroxyl groups of the polymers of the carrier, between the elements bonded to hydroxyl groups of the polymers of the carrier, between hydroxyl groups of boron, and / or between the element bonded to hydroxyl groups of the polymers of the carrier and hydroxyl groups of the polymers of the carrier.

[0012] In various embodiments, the element is covalently bonded to the hydroxyl groups of the carrier.

[0013] In various embodiments, the element is a metal cation. For example, the element may be Fe2+, Fe3+, Mn2+, Cu+, Cu2+, Ca2+, Mg2+, Mo4+, Mo6+or Zn2+. For example, the element may be Fe2+, Fe3+, Ca2+or Zn2+.

[0014] In various embodiments, the boron is crosslinked as a diol to the element.

[0015] In various embodiments, the boron is bonded to the hydroxyl groups of the carrier.

[0016] In various embodiments, the carrier comprises cellulose and starch.

[0017] In various embodiments, the carrier further comprises cellulose fibre.

[0018] In various embodiments, the composition comprises at least about 5% (wt / wt) of the element, based on the total weight of the composition.

[0019] In various embodiments, the composition comprises between about 1 % and about 5% (wt / wt) of the element, based on the total weight of the composition.

[0020] In various embodiments, the composition comprises between about 1 % and about 6% (wt / wt) of boron, based on the total weight of the composition.

[0021] In various embodiments, the composition comprises between about 1 % and about 3% (wt / wt) of boron, based on the total weight of the composition.

[0022] In various embodiment, the carrier comprises pea starch, lentil starch, oat starch, potato starch, sweet potato starch, corn starch, bean starch, cassava starch, wheat starch, rice starch, sorghum starch, millet starch, taro starch, yam starch, arrow root starch, sago palm starch, plantains starch, banana starch, squash starch or a combination thereof.

[0023] In various embodiments, the carrier comprises pea hull, lentil hull, oat fibre, potato fibre, sweet potato fibre, corn fibre, bean fibre, cassava fibre, wheat hull, rice husk, sorghum hull, millet hull, taro hull, yam fibre, arrowroot fibre, sago palm fibre, plantains fibre, banana fibre, squash fibre or a combination thereof.

[0024] Various aspects of the present disclosure also provide a method for preparing a composition as disclosed herein, the method comprising: reacting a boron source with an aqueous hydroxide base to generate borate ions in an alkali media; adding a carrier comprising cellulose and / or starch to the alkali media, wherein addition of the carrier to the alkali media deprotonates hydroxyl groups of the cellulose and / or starch of the carrier; adding a solution of ions of an element to the alkali media to form a mixture; and heating the mixture to form the composition.

[0025] In various embodiments, the boron source is boric acid or a borate salt.

[0026] In various embodiments, the borate coordinates with cellulose and / or starch when the carrier is added to the alkali media.

[0027] In various embodiments, the aqueous hydroxide base comprises potassium hydroxide, sodium hydroxide or a combination thereof.

[0028] In various embodiments, the element is a metal cation and the solution of ions of the element is prepared by dissolution of a salt of the metal cation in water.

[0029] In various embodiments, the element is zinc, iron or calcium, and the solution of ions is prepared by dissolution of ZNSO4 H2O, FeSCM JFW or CaCl2'2H2O, respectively, in water.

[0030] In various embodiments, the carrier comprises pea starch, lentil starch, oat starch, potato starch, sweet potato starch, corn starch, bean starch, cassava starch, wheat starch, rice starch, sorghum starch, millet starch, taro starch, yam starch, arrow root starch, sago palm starch, plantains starch, banana starch, squash starch or a combination thereof.

[0031] In various embodiments, the carrier comprises pea hull, lentil hull, oat fibre, potato fibre, sweet potato fibre, corn fibre, bean fibre, cassava fibre, wheat hull, rice husk, sorghum hull, millet hull, taro hull, yam fibre, arrowroot fibre, sago palm fibre, plantains fibre, banana fibre, squash fibre or a combination thereof.

[0032] In various embodiments, the heating is between about 20°C to about 85°C.

[0033] Various aspects of the present disclosure further provide a method for preparing a composition as disclosed herein, the method comprising: combining solid boric acid with a carrier comprising cellulose and / or starch; activating hydroxyl groups of the carrier to form an alkali media; adding a solution of ions of an element to the alkali media to form a mixture; and heating the mixture to form the composition.

[0034] In various embodiments, activating hydroxyl groups of the carrier comprises adding an aqueous hydroxide base to form the alkali media, wherein addition of the aqueous hydroxide base generates borate ions in situ and deprotonates hydroxide groups of the cellulose and / or starch of the carrier.

[0035] In various embodiments, the method further comprises mixing the alkali media for about 15 minutes to about 60 minutes before adding the solution of ions of the element.

[0036] In various embodiments, borate coordinates with cellulose and / or starch when the aqueous hydroxide base is added to the solid boric acid and the carrier.

[0037] In various embodiments, the aqueous hydroxide base comprises potassium hydroxide, sodium hydroxide or a combination thereof.

[0038] In various embodiments, the hydroxyl groups of the carrier are activated electrochemically to form the alkali media.

[0039] In various embodiments, the element is a metal cation and the solution of ions of the element is prepared by dissolution of a salt of the metal cation in water.

[0040] In various embodiments, the element is zinc, iron or calcium, and the solution of ions is prepared by dissolution of ZNSO4 H2O, FeSCM JFW or CaCl2'2H2O, respectively, in water.

[0041] In various embodiments, the carrier comprises pea starch, lentil starch, oat starch, potato starch, sweet potato starch, corn starch, bean starch, cassava starch, wheat starch, rice starch, sorghum starch, millet starch, taro starch, yam starch, arrowroot starch, sago palm starch, plantains starch, banana starch, squash starch or a combination thereof.

[0042] In various embodiments, the carrier comprises pea hull, lentil hull, oat fibre, potato fibre, sweet potato fibre, corn fibre, bean fibre, cassava fibre, wheat hull, rice husk, sorghum hull, millet hull, taro hull, yam fibre, arrowroot fibre, sago palm fibre, plantains fibre, banana fibre, squash fibre or a combination thereof.

[0043] In various embodiments, the heating is between about 20°C to about 85°C.

[0044] Other aspects and features of the present invention will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In drawings which illustrate embodiments of the disclosure,

[0046] Figure 1 shows examples of structures and interactions formed within embodiments of the compositions of the disclosure, including mono-chelation and cross-linking interactions. Figure 1 (A) shows hydrogen bonding between borate and the carrier, Figure 1 (B) shows covalent interactions between borate and the carrier, and Figure 1 (C) shows covalent interactions between the carrier, borate and an element.

[0047] Figure 2 shows a timescale release of boron from two reference materials (boric acid and Borax) compared to boron release from an iron-boron composition, a zinc-boron composition, and a calcium-boron composition according to embodiments of the disclosure.

[0048] Figure 3 shows a timescale release of boron from a reference material (boric acid) compared to boron release from zinc boron compositions according to embodiments of the disclosure.

[0049] Figure 4 shows a timescale release of boron from Aspire Boron compared to boron release from zinc boron compositions according to embodiments of the disclosure.

[0050] Figure 5 shows percentage boron leached from a reference material (Borax) compared to percentage boron release from zinc boron compositions according to embodiments of the disclosure and boron concentration of leachate from soil columnsas a function of number of irrigations for the reference material (Borax) compared to the zinc boron compositions according to embodiments of the disclosure.DETAILED DESCRIPTION

[0051] In the context of the present disclosure, various terms are used in accordance with what is understood to be the ordinary meaning of those terms.

[0052] In various embodiments, the disclosure provides compositions for providing boron to plants. Boron is an important nutrient for plant growth, however, the range of boron in soil between that which promotes plant growth and that which is toxic to plants is narrow, mainly due to the solubility of boron-containing compounds in water. The boron-containing compositions as described herein have reduced solubility in water compared to other boron-containing fertilizers, compounds and compositions, but also provide boron to plants in bioavailable form. For example, the compositions may interact with the microbiome of soils in order to release nutrients to plants. By having reduced solubility in water compared to other boron-containing compounds and compositions, boron toxicity to plants is reduced as less boron leaches into the soil, thereby providing boron to plants to improve crop growth without the negative effects associated with boron toxicity. Furthermore, the compositions as disclosed herein are easy to apply to soils due to this reduced toxicity, and there are broader ranges of application rates and application amounts that can be used compared to other boron fertilizers and boron-containing compounds and compositions.

[0053] The compositions disclosed herein comprise a carrier comprising cellulose and / or starch, wherein the carrier is a network of polymers; an element bonded to hydroxyl groups of the polymers of the carrier; and boron bonded directly and / or indirectly to the carrier, wherein boron bonded directly to the carrier comprises bonding to hydroxyl groups of the carrier and boron bonded indirectly to the carrier comprises bonding of boron to the element.

[0054] Cellulose is a polysaccharide consisting of a linear chain of [3(1 — >4) linked D- glucose units having the formula (CeH Osjn and comprising aliphatic hydroxyl groups and phenolic hydroxyl groups. Starch is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. It consists of two types of molecules, the linear and helical amylose, and the branched amylopectin. Starch alsocomprises aliphatic hydroxyl groups and phenolic hydroxyl groups. In various embodiments, the carrier comprises cellulose or starch. In various embodiments, the carrier consists of cellulose and starch. In various embodiments, the carrier may further comprise cellulose fibre. The term “fibre” refers to a component of plant material that is not soluble in water. The carrier may be from a natural source or synthetically produced.

[0055] In various embodiments, the carrier comprises pea starch, lentil starch, oat starch, potato starch, sweet potato starch, corn starch, bean starch, cassava starch, wheat starch, rice starch, sorghum starch, millet starch, taro starch, yam starch, arrow root starch, sago palm starch, plantains starch, banana starch, squash starch or a combination thereof.

[0056] In various embodiments, the carrier comprises pea hull, lentil hull, oat fibre, potato fibre, sweet potato fibre, corn fibre, bean fibre, cassava fibre, wheat hull, rice husk, sorghum hull, millet hull, taro hull, yam fibre, arrowroot fibre, sago palm fibre, plantains fibre, banana fibre, squash fibre or a combination thereof.

[0057] The term “element” refers to an ion that bonds to hydroxyl groups of the polymers of the carrier. For example, the element may be a metal cation. For example, the element may be Fe2+, Fe3+, Mn2+, Cu+, Cu2+, Ca2+, Mg2+, Mo4+, Mo6+or Zn2+. In various embodiments, the element may be Fe2+, Fe3+, Ca2+or Zn2+.

[0058] In various embodiments, the boron of the compositions as disclosed herein is a nutrient that sustains an organism in its existence, by promoting organism growth, replacing loss and / or providing energy. Boron can be taken into the organism by any means that the organism uses to take in nutrients. For example, if the organism is a plant, it typically absorbs nutrients through its roots and leaves. In various embodiments, the boron is in a biologically available form. The term “biologically available form” means that a micronutrient is present in an oxidation state that allows for transport across a cellular membrane without requiring a reduction or change in oxidation state prior to cross-membrane transport. For example, B3+is the oxidation state of boron that is a biologically available form of this nutrient.

[0059] The boron is bonded directly or indirectly to the carrier. The terms “bond”, “bonded” or “bonding” refer an association between atoms that enables the formation of ions, molecules and other structures. The association may comprise adsorption,covalent bonding, ionic interactions, hydrogen bonding, Van der Waals interactions, or any combination thereof. Direct bonding of boron to the carrier comprises bonding of boron to hydroxyl groups of the carrier. Indirect bonding of boron to the carrier comprises bonding of boron to the element.

[0060] Figure 1 shows various structures and interactions between the carrier, the element and boron. These structures and interactions may include mono-chelation and cross-linking interactions. For example, the boron may be a crosslinking agent between polymers of the carrier, wherein the crosslinking is between hydroxyl groups of the polymers of the carrier, between the elements bonded to hydroxyl groups of the polymers of the carrier, between hydroxyl groups of boron, and / or between the element bonded to hydroxyl groups of the polymers of the carrier and hydroxyl groups of the polymers of the carrier. Figure 1 (A) shows hydrogen bonding between boron, in the form of borate ions, with hydroxyl groups of the carrier. Figure 1 (B) shows covalent bonding between boron, in the form of borate ions, with hydroxyl groups of the polymers of the carrier. Figure 1 (C) shows bonding of boron with the element. In these examples, the element is covalently bonded to hydroxyl groups of the polymers of the carrier. The bonding between boron, in the form of borate ions, and the element is covalent bonding in these examples. The boron may also be crosslinked as a diol to the element. The interactions between the carrier, the element and boron are not limited to these examples.

[0061] In various embodiments, the composition comprises at least about 1% (wt / wt) of the element, based on the total weight of the composition. In various embodiments, the composition comprises at least about 2% (wt / wt) of the element, based on the total weight of the composition. In various embodiments, the composition comprises at least about 4% (wt / wt) of the element, based on the total weight of the composition. In various embodiments, the composition comprises at least about 5% (wt / wt) of the element, based on the total weight of the composition. In various embodiments, the composition comprises between about 1 % (wt / wt) and about 5% (wt / wt) of the element, based on the total weight of the composition, or any amount therebetween.

[0062] In various embodiments, the compositions comprises at least about 1 % (wt / wt) of boron, based on the total weight of the composition. In various embodiments, the composition comprises at least about 2% (wt / wt) of boron, based on the total weightof the composition. In various embodiments, the composition comprises at least about 3% (wt / wt) of boron, based on the total weight of the composition. In various embodiments, the composition comprises at least about 4% (wt / wt) of boron, based on the total weight of the composition. In various embodiments, the composition comprises at least about 5% (wt / wt) of boron, based on the total weight of the composition. In various embodiments, the composition comprises at least about 6% (wt / wt) of boron, based on the total weight of the composition. In various embodiments, the composition comprises between about 1 % (wt / wt) and about 3% (wt / wt) of boron, based on the total weight of the composition, or any amount therebetween. In various embodiments, the composition comprises between about 1 % (wt / wt) and about 6% (wt.wt) of boron, based on the total weight of the composition.

[0063] In various embodiments, the composition is resistant to boron leaching in water. In various embodiments, the composition may minimize or decrease boron leaching into water sources.

[0064] In various embodiments, the composition may be non-toxic. For example, the composition does not cause nutrient toxicity when deployed in high concentrations. The compositions may be non-toxic to plants, humans and animals.

[0065] In various embodiments, the composition may be added to an environment of a plant in order to increase growth of the plant. The environment may be an agricultural field or soil. In various embodiments, the composition may be applied to soil.

[0066] The compositions disclosed herein may be prepared by reacting a boron source with an aqueous hydroxide base to generate borate ions in an alkali media, adding a carrier comprising cellulose and / or starch to the alkali media, wherein addition of the carrier to the alkali media deprotonates hydroxyl groups of the cellulose and / or starch of the carrier, adding a solution of ions of an element to the alkali media to form a mixture; and heating the mixture to form the composition.

[0067] In various embodiments, the boron source is boric acid or a borate salt. In various embodiments, the boron source is boric acid. The boric acid reacts with the aqueous hydroxide base to generate borate ions in an alkali media. In various embodiments, the aqueous hydroxide base comprises potassium hydroxide, sodium hydroxide or a combination thereof. In various embodiments, the aqueous hydroxide base is potassium hydroxide. Addition of the carrier to the alkali media results indeprotonation of the cellulose and / or starch hydroxide groups as well as coordination of borate to cellulose and / or starch fibers. The solution of ions of an element may be prepared by dissolution of a metal salt. For example, the element may be a metal cation and the solution of ions of the element is prepared by dissolution of a salt of the metal cation in water. In various embodiments, the element may be zinc, iron or calcium, and the solution of ions is prepared by dissolution of ZnSCU FbO, FeSO4'7H2O or CaCl2'2H2O, respectively, in water. This solution is added with subsequent heating to drive reactivity and eliminate water, which is a by-product of cellulose and / or starch deprotonation and boroester formation. For example, the heating may be to a temperature of about 20°C to about 85°C.

[0068] An alternative method for preparing the compositions as disclosed herein comprises combining solid boric acid with a carrier comprising cellulose and / or starch, activating hydroxyl groups of the carrier to form an alkali media; adding a solution of ions of an element to the alkali media to form a mixture; and heating the mixture to form the composition. This method uses a single reactor for the complete synthesis.

[0069] Initially, boric acid in solid form is combined with the carrier comprising cellulose and / or starch.

[0070] Activating hydroxyl groups of the carrier to form the alkali media may comprise adding an aqueous hydroxide base to form the alkali media, wherein addition of the aqueous hydroxide base generates borate ions in situ and deprotonates hydroxide groups of the cellulose and / or starch of the carrier. In various embodiments, the alkali media is mixed for about 15 minutes to about 60 minutes before adding the solution of ions of the element. In various embodiments, borate coordinates with cellulose and / or starch when the aqueous hydroxide base is added to the solid boric acid and the carrier. In various embodiments, the aqueous hydroxide base may be potassium hydroxide, sodium hydroxide or a combination thereof. In various embodiments, the element is a metal cation and the solution of ions of the element is prepared by dissolution of the metal cation in water. For example, the element may be zinc, iron or calcium, and the solution of ions is prepared by dissolution of ZnSO-iTW, FeSO4'7H2O or CaCl2'2H2O, respectively, in water.

[0071] In alternative embodiments, hydroxyl groups of the carrier may be activated electrochemically to form the alkali media.

[0072] The solution of ions of the element is added to the alkali media with subsequent heating to drive reactivity and eliminate water, which is a by-product of cellulose and / or starch deprotonation and boroester formation. For example, the heating may be to a temperature of about 20°C to about 85°C.EXAMPLES

[0073] These examples illustrate various aspects of the invention, evidencing a variety of conditions for preparing compositions comprising a carrier comprising cellulose and / or starch; an element bonded to hydroxyl groups of the polymers of the carrier; and boron bonded directly or indirectly to the carrier, wherein boron bonded directly to the carrier comprises bonding of boron to hydroxyl groups of the carrier and boron bonded indirectly to the carrier comprises bonding of boron to the element. Selected examples are illustrative of advantages that may be obtained compared to alternative methods, and these advantages are accordingly illustrative of particular embodiments and not necessarily indicative of the characteristics of all aspects of the invention.

[0074] As used herein, the term “about” refers to an approximately + / -10% variation from a given value. It is to be understood that such a variation is always included in any given value provided herein, whether or not it is specifically referred to.Example 1: Preparation of a zinc-boron composition

[0075] 20 grams of boric acid was mixed with 80 mL of distilled water at room temperature, and 18 g of solid potassium hydroxide was added to the mixture. The suspension was mixed until a clear solution formed, indicating that borate had formed from the boric acid. The solution was then cooled to room temperature. In a separate container, 100 g of pea fiber was combined with the solution using continuous mixing. Following the addition, the material (the alkali media) was mixed for an additional 30 minutes. In a separate container, 29 g of zinc sulfate monohydrate was mixed and dissolved in 80 mL of distilled water and heated to approximately 70°C. The alkali media was then added and mixed for 30 minutes, then heated to approximately 65°C with mixing for about one hour. The material was then transferred to a drying oven anddried for approximately 12 hours at a temperature of about 60°C, or until the moisture content was below 10% w / w.Example 2: Preparation of an iron-boron composition

[0076] 20 grams of boric acid was mixed with 80 mL of distilled water at room temperature, and 18 g of solid potassium hydroxide was added to the mixture. The suspension was mixed until a clear solution formed, indicating that borate had formed from the boric acid. The solution was then cooled to room temperature. In a separate container, 100 g of pea fiber was combined with the solution using continuous mixing. Following the addition, the material (the alkali media) was mixed for an additional 30 minutes. In a separate container, 45 g of iron sulfate heptahydrate was mixed in 80 mL of distilled water and heated to approximately 70°C with mixing until the iron sulfate was dissolved. The previous material was then added and mixed for 30 minutes, then heated to approximately 65°C with mixing for about one hour. The material was then transferred to a drying oven and dried for approximately 12 hours at a temperature of about 60°C, or until the moisture content was below 10% w / w.Example 3: Preparation of a calcium-boron composition

[0077] 20 grams of boric acid was mixed with 80 mL of distilled water at room temperature, and 18 g of solid potassium hydroxide was added to the mixture. The suspension was mixed until a clear solution formed, indicating that borate had formed from the boric acid. The solution was then cooled to room temperature. In a separate container, 100 g of pea fiber was combined with the solution using continuous mixing. Following the addition, the material (the alkali media) was mixed for an additional 30 minutes. In a separate container, 18 g of calcium chloride dihydrate was mixed in 80 mL of distilled water and heated to approximately 70°C with mixing until the calcium chloride was dissolved. The previous material was then added and mixed for 30 minutes, then heated to approximately 65°C with mixing for about one hour. The material was then transferred to a drying oven and dried for approximately 12 hours at a temperature of about 60°C, or until the moisture content was below 10% w / w.Example 4: Preparation of a zinc-boron composition according to an alternative method

[0078] 100 grams of pea fiber was placed in a container and 20 g of boric acid was added. In a separate container, 18 g of potassium hydroxide was dissolved in 80 mL of distilled water. This solution was allowed to cool to room temperature. The two materials were combined with continuous mixing and then mixed for an additional 30 minutes. In a separate container, 29 g of zinc sulfate monohydrate was mixed with 80 mL of distilled water and the solution was heated to 70°C to aid dissolution of the zinc sulfate monohydrate. The two solutions were combined with continuous mixing and then mixed for an additional 30 minutes, heated to 65°C and mixed for an additional 60 minutes. The material was then transferred to a drying oven and dried for approximately 12 hours at a temperature of about 60°C, or until the moisture content was below 10% w / w.Example 5: Characterization of compositions produced in Examples 1 , 2 and 3

[0079] The compositions produced in Examples 1 , 2 and 3 were analyzed for boron and metal contents, as shown in Table 1 . Percentage boron content was the measured content of boron in the compositions as determied by inductively coupled plasma-mass spectrometry (ICP-MS) and the percentage metal content was the measured concentration of metal (zinc, iron or calcium) as determined by X-ray fluorometry (XRF).Table 1 . Boron and metal content of compositions of Examples 1 , 2 and 3Example 6: Timescale release of boron into water from compositions produced in Examples 1 , 2 and 3

[0080] Samples of the compositions of Examples 1 , 2 and 3 were placed in water and the amount of boron in the water over time was measured to determine the leaching of boron from the composition into the water. The results are shown graphically in Figure 2 and summarized in Table 2. Two reference compounds werealso tested for their dissolution in water, these being boric acid and Borax (sodium tetraborate decahydrate). In Figure 2, RZ293 refers to the Fe-Boron composition of Example 2, RZ291 refers to the Zn-Boron composition of Example 1 , and RZ294 refers to the Ca-Boron Composition of Example 3.Table 2. Timescale of the release of boron from reference material and samples of the compositions of Examples 1 (Zn-Boron Composition), 2 (Fe-Boron Composition) and 3 (Ca-Boron Composition)

[0081] As can be seen from Figure 2 and Table 2, the rate of release of boron from the samples of compositions of Examples 1 , 2 and 3 are significantly reduced compared to reference materials boric acid and borax. Thus, the compositions as disclosed herein bond boron such that it does not or minimally leaches into water and / or soil, such that it is in bioavailable form for uptake by plants without damaging water and / or soil resources.Example 7: pH of Compositions of Examples 1 , 2 and 3

[0082] Soil pH is an important variable for crop growth. The optimal range for most crops is between about 5.5 and about 7.5, although some crops have adapted to thrive outside of this range. Adding excessively acidic or alkaline material to soil may negatively affect performance. To aid in understanding the effects of the compositions as disclosed herein on soil pH, samples of the composition were placed in water and a pH of the water was measured. Although this experiment does not indicate soil pH, it is indicative of potential effects of the compositions on soil pH. The results were alsocompared against boric acid and borax in water, as references. As shown in Table 3, the water containing the compositions of Examples 1 , 2 and 3 did not have excessively acidic or alkaline pH, indicating that the compositions are appropriate for use in soil.Table 3. Analysis of pH of water containing reference materials (boric acid and borax) and samples of the compositions of Examples 1 (Zn-Boron Composition), 2 (Fe-Boron Composition) and 3 (Ca-Boron Composition)Example 8: Modification of Synthesis Method for Zinc-Boron Composition of Example 1

[0083] Different variables for the synthesis of the zinc-boron composition of Example 1 were modified to determine the effect on % boron content of composition, % boron released from composition after soaking in water for 24 hours, pH of water after adding composition to water, % zinc content of composition, and % zinc released from composition after soaking composition in water for one hour. The variables modified were mass of boric acid used in the synthesis, mass of zinc sulfate monohydrate used in the synthesis, mass of potassium hydroxide used in the synthesis, length of mixing time after adding solution of zinc ions to the alkali media and temperature for heating to mix the solution of zinc ions and alkali media to form the composition. The variables as modified are shown in Table 4. In each case, the synthesis was performed with 100g of a cellulose substrate (pea fiber) and the method was consistent with that described in Example 1 .Table 4. Summary of variables as modified for the synthesis of a zinc-boron composition

[0084] The resulting compositions, referred to as Z1 , Z2, Z3 and Z4, were tested for % boron content of composition, % boron released from composition after soaking in water for 24 hours, pH of water after adding composition to water, % zinc content of composition, and % zinc released from composition after soaking composition in water for one hour, as shown in Table 5. The results show that the listed variables could be modified and still produce compositions that release boron over time and without releasing significant amounts of zinc, thereby providing boron to plants without creating toxicity to the plants or soils.Table 5. Summary of properties of compositions Z1 , Z2, Z3 and Z4Example 9: Modification of Synthesis Method for Iron-Boron Composition of Example 2

[0085] Different variables for the synthesis of the iron-boron composition of Example 2 were modified to determine the effect on % boron content of composition, % boron released from composition after soaking in water for 24 hours, pH of water after adding composition to water, % iron content of composition, and % iron released from composition after soaking composition in water for one hour. The variables modified were mass of boric acid used in the synthesis, mass of iron sulfate heptahydrate used in the synthesis, mass of potassium hydroxide used in the synthesis, length of mixing time after adding solution of iron ions to the alkali media and temperature for heating to mixthe solution of iron ions and alkali media to form the composition. The variables as modified are shown in Table 6. In each case, the synthesis was performed with 100g of a cellulose substrate (pea fiber) and the method was consistent with that described in Example 2.Table 6. Summary of variables as modified for the synthesis of an iron-boron composition

[0086] The resulting compositions, referred to as 11 , I2, I3 and I4, were tested for % boron content of composition, % boron released from composition after soaking in water for 24 hours, pH of water after adding composition to water, % iron content of composition, and % iron released from composition after soaking composition in water for one hour, as shown in Table 7. The results show that the listed variables could be modified and still produce compositions that release boron over time and without releasing significant amounts of iron, thereby providing boron to plants without creating toxicity to the plants or soils.Table 7. Summary of properties of compositions 11 , I2, I3 and I4Example 10: Timescale release of boron into water from compositions produced in Example 4

[0087] Two different groups of samples were prepared according to the method of Example 4, one referred to as a “low boron product” and the other referred to as a “high boron product”. Multiple samples of each were prepared to ensure analytical responses were identical and that the synthesis method was reproducible. The samples were analyzed for boron and metal contents, pH and initial zinc release, as shown in Table 8. Percentage boron and zinc contents was the measured content of boron in the compositions as determied by inductively coupled plasma-mass spectrometry (ICP-MS) and the percentage metal content was the measured concentration of metal (zinc, iron or calcium) as determined by X-ray fluorometry (XRF). The compositions did not release significant amounts of zinc, thereby providing boron to plants without creating toxicity to the plants or soils.Table 8. Boron and metal content, pH and initial zinc release of compositions of Example 4

[0088] Samples of the compositions of Example 4 were placed in water and the amount of boron in the water over time was measured to determine the leaching of boron from the composition into the water. The results are shown graphically in Figure 3 and summarized in Table 9. A reference compound of boric acid was also tested for its dissolution in water. Both groups of samples release boron much slower than boric acid.Table 9. Average boron leaching values for compositions of Example 4

[0089] Samples of the compositions of Example 4 were placed in water and the amount of boron in the water over time was measured to determine the leaching of boron from the compositions into the water compared to a commercially available boron fertilizer branded as Aspire Boron from Mosaic. The results are shown graphically in Figure 4 and summarized in Table 10.Table 10. Average boron leaching values for compositions of Example 4 compared to Aspire Boron as a function of timeExample 11 : Soil column leaching of boron from compositions produced in Example 4

[0090] Soil columns were prepared which contained the composition prepared according to Example 4. The soil columns were incubated for 66 days at 22°C and 70% humidity. Irrigations of adding water to the soild columns were carried out every 7 days and the water samples were collected from the bottom of the column for measurementto determine the % of boron leached from the composition and the boron concentration in the leachate. The results are shown in Figure 5. Use of the compositions as disclosed herein resulted in less boron being leached from the composition as compared to Borax and less boron in the leachate. Thus, compositions as disclosed herein release boron over time, thereby providing boron to plants without creating toxicity to the plants or soils.

[0091] Although various embodiments of the invention are disclosed herein, many adaptations and modifications may be made within the scope of the invention in accordance with the common general knowledge of those skilled in this art. Such modifications include the substitution of known equivalents for any aspect of the invention in order to achieve the same result in substantially the same way. Numeric ranges are inclusive of the numbers defining the range. The word "comprising" is used herein as an open-ended term, substantially equivalent to the phrase "including, but not limited to", and the word "comprises" has a corresponding meaning. As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a thing" includes more than one such thing. Citation of references herein is not an admission that such references are prior art to the present invention. Any priority document(s) and all publications, including but not limited to patents and patent applications, cited in this specification are incorporated herein by reference as if each individual publication were specifically and individually indicated to be incorporated by reference herein and as though fully set forth herein. The invention includes all embodiments and variations substantially as hereinbefore described and with reference to the examples and drawings. 1

Claims

CLAIMS1 . A composition comprising: a carrier comprising cellulose and / or starch, wherein the carrier is a network of polymers; an element bonded to hydroxyl groups of the polymers of the carrier; and boron bonded directly and indirectly to the carrier, wherein boron bonded directly to the carrier comprises bonding of boron to hydroxyl groups of the carrier and boron bonded indirectly to the carrier comprises bonding of boron to the element.

2. The composition of claim 1 , wherein the boron is a crosslinking agent between polymers of the carrier, wherein the crosslinking is between hydroxyl groups of the polymers of the carrier, between the elements bonded to hydroxyl groups of the polymers of the carrier, between hydroxyl groups of boron, and / or between the element bonded to hydroxyl groups of the polymers of the carrier and hydroxyl groups of the polymers of the carrier.

3. The composition of claim 1 or 2, wherein the element is Fe2+, Fe3+, Mn2+, Cu+, Cu2+, Ca2+, Mg2+, Mo4+, Mo6+or Zn2+.

4. The composition of any one of claims 1 to 3, wherein the boron is crosslinked as a diol to the element.

5. The composition of any one of claims 1 to 3, wherein the boron is bonded to the hydroxyl groups of the carrier.

6. The composition of any one of claims 1 to 5, wherein the carrier comprises cellulose and starch.

7. The composition of any one of claims 1 to 6, wherein the carrier further comprises cellulose fibre.

8. The composition of any one of claims 1 to 7, wherein the composition comprises at least about 5% (wt / wt) of the element, based on the total weight of the composition.

9. The composition of any one of claims 1 to 7, wherein the composition comprises between about 1 % and about 5% (wt / wt) of the element, based on the total weight of the composition.

10. The composition of any one of claims 1 to 9, wherein the composition comprises between about 1 % and about 6% (wt / wt) of boron, based on the total weight of the composition.11 . The composition of any one of claims 1 to 9, wherein the composition comprises between about 1 % and about 3% (wt / wt) of boron, based on the total weight of the composition.

12. The composition of any one of claims 1 to 11 , wherein the carrier comprises pea starch, lentil starch, oat starch, potato starch, sweet potato starch, com starch, bean starch, cassava starch, wheat starch, rice starch, sorghum starch, millet starch, taro starch, yam starch, arrow root starch, sago palm starch, plantains starch, banana starch, squash starch or a combination thereof.

13. The composition of any one of claims 1 to 12, wherein the carrier comprises pea hull, lentil hull, oat fibre, potato fibre, sweet potato fibre, com fibre, bean fibre, cassava fibre, wheat hull, rice husk, sorghum hull, millet hull, taro hull, yam fibre, arrowroot fibre, sago palm fibre, plantains fibre, banana fibre, squash fibre or a combination thereof.

14. A method for preparing a composition as defined in any one of claims 1 to 13, the method comprising: reacting a boron source with an aqueous hydroxide base to generate borate ions in an alkali media; adding a carrier comprising cellulose and / or starch to the alkali media, wherein addition of the carrier to the alkali media deprotonates hydroxyl groups of the cellulose and / or starch of the carrier;adding a solution of ions of an element to the alkali media to form a mixture; and heating the mixture to form the composition.

15. The method of claim 14, wherein the boron source is boric acid or a borate salt, and the aqueous hydroxide base comprises potassium hydroxide, sodium hydroxide or a combination thereof.

16. A method for preparing a composition as defined in any one of claims 1 to 13, the method comprising: combining solid boric acid with a carrier comprising cellulose and / or starch; activating hydroxyl groups of the carrier to form an alkali media; adding a solution of ions of an element to the alkali media to form a mixture; and heating the mixture to form the composition.

17. The method of claim 16, wherein activating hydroxyl groups of the carrier comprises adding an aqueous hydroxide base to form the alkali media, wherein addition of the aqueous hydroxide base generates borate ions in situ and deprotonates hydroxide groups of the cellulose and / or starch of the carrier.

18. The method of claim 17, wherein borate coordinates with cellulose and / or starch when the aqueous hydroxide base is added to the solid boric acid and the carrier.

19. The method of claim 17 or 18, wherein the aqueous hydroxide base comprises potassium hydroxide, sodium hydroxide or a combination thereof.

20. The method of any one of claims 14 to 19, wherein the element is zinc, iron or calcium, and the solution of ions is prepared by dissolution of ZNSO4 H2O, FeSCM JFW or CaCl2'2H2O, respectively, in water.

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