WO2011059328A1

WO2011059328A1 - Soil supplement comprising olivine and calcium salts

Info

Publication number: WO2011059328A1
Application number: PCT/NL2010/050754
Authority: WO
Inventors: Alexei Adolfovich Ogrel; Pier Jouke Oosterkamp
Original assignee: A.J. Zwart Beheer B.V.
Priority date: 2009-11-12
Filing date: 2010-11-12
Publication date: 2011-05-19
Also published as: NL2003797C2

Abstract

The invention relates to the field of agriculture. In particular, it relates to compositions comprising olivine for use as a soil p H neutralizer, soil conditioner and/or soil fertilizer. Provided is a soil supplement composition comprising olivine and at least one fertilizing calcium salt, wherein the relative weight ratio between said olivine and the total amount of said calcium salt is between 2:1 and 9:1 and wherein the composition has a relative neutralizing value of at least 25. The composition may further comprise at least one micro-organism capable of solubilizing the at least one calcium salt.

Description

SOIL SUPPLEMENT COMPRISING OLIVINE AND CALCIUM SALTS

The invention relates to the field of agriculture. In particular, it relates to compositions comprising olivine for use as a soil conditioner and/or fertilizer. The present invention also relates to processes for forming such compositions as well as to methods of introducing nutrient values into cultivated soil so as to improve utilization of the nutrient values by plants grown in the soil.

Fertilizers typically provide, in varying proportions, the three major plant nutrients: nitrogen, phosphorus, potassium (known shorthand as N-P-K); the secondary plant nutrients (calcium, sulphur, magnesium) and trace elements (or micronutrients): boron, chlorine, manganese, iron, zinc, copper, molybdenum and (in some countries) selenium.

Soil conditioners or liming agents are widely used in agriculture, lawn care and gardening to reduce soil acidity and promote plant health. A variety of calcium-containing materials, in particulate or granulated form, are used as soil liming agents. Agricultural lime, also called aglime, garden lime or liming, is a soil additive typically made from pulverized limestone or chalk. The primary active component is calcium carbonate. Additional chemicals vary depending on the mineral source and may include calcium oxide, magnesium oxide and magnesium carbonate. Lime increases the pH of acidic soil, it provides a source of calcium for plants and it permits improved water penetration for acidic soils. Calcium is an important element of cell walls and an integral part of chromosomes' structure. This secondary element helps to regulate a plants' enzyme activity which in its turn secures the uptake of other nutritious elements, particularly nitrogen. Calcium helps to strengthen grain- crops' stems, increases the hull solidity and improves the color and the quality of tubers, roots and fruits and reduces the losses in storage of agricultural products. Lime may occur naturally in some soils but may require addition of sulphuric acid for its agricultural benefits to be realized. Gypsum is also used to supply calcium for plant nutrition. The concept of "corrected lime potential" to define the degree of base saturation in soils became the basis for procedures now used in soil testing laboratories to determine the "lime requirement" of soils ("One Hundred Harvests Research Branch Agriculture Canada 1886- 1986". Historical series / Agriculture Canada - Serie historique / Agriculture Canada. Government of Canada). Other forms of lime have common

applications in agriculture and gardening, including dolomitic lime and hydrated lime. Dolomitic lime may be used as a soil input to provide similar effects as agricultural lime, while supplying magnesium in addition to calcium.

Thus, conventional liming compositions based on calcium carbonate are very effective to neutralize soil acidity and provide a source of nutrient values. However, a major drawback resides in the fact that agricultural lime provides a significant contribution to carbon dioxide emission. See for example West et al. (Agriculture, Ecosystems & Environment, Vol. 108, Issue 2, 2005, pp. 145-154). It is clear that the use of lime comes at a high prize with respect to climate change concerns.

Therefore, it would be advantageous to provide an alternative for agricultural liming agents that allow for conditioning and improving the soil in a more sustainable and environment-friendly fashion. In particular, the inventors sought to provide a fertilizing composition that is useful not only to raise the pH of acidic soil and provide calcium for plants, but which also contributes to capturing CO2 from the atmosphere.

This goal was met by the provision of a soil supplement composition comprising olivine, at least one fertilizing calcium salt, wherein the relative weight ratio between said olivine and the total amount of said calcium salt is between 2:1 and 9:1 and wherein the composition has a relative neutralizing value (NV) of at least 25. To accommodate for both the soil neutralizing effect and the calcium requirement of most plants, it was found that the relative weight ratio between olivine and the total amount of calcium salt must range between 2:1 and 9:1. For example, the relative weight ratio is between 3:1 and 5:1, preferably about 4:1. The mineral olivine (when gem-quality also called peridot) is a magnesium iron silicate with the formula (Mg,Fe)2Si04. It is one of the most common minerals on Earth. The ratio of magnesium and iron varies between the two end members of the solid solution series: forsterite (Mg-end member) and fayalite (Fe-end member). Compositions of olivine are commonly expressed as molar percentages of forsterite (Fo) and fayalite (Fa) (e.g., Fo₇oFa3o).

Forsterite has an unusually high melting temperature at atmospheric pressure, almost 1900°C, but the melting temperature of fayalite is much lower (about 1200°C). As to the relative contribution of forsterite versus fayalite, the invention can be performed with any type of olivine. For example, the olivine in a composition of the invention contains at least 50 mole% forsterite. As another example, the olivine in a composition of the invention contains at least 50 mole% fayalite. Olivine incorporates only minor amounts of elements other than oxygen, silicon, magnesium, and iron. Manganese and nickel commonly are the additional elements present in highest

concentrations.

The use of olivine in agricultural applications is known in the art. For example, WO2005/097947 is directed to a soil supplement and process for application of the supplement that improves plant uptake primarily of phosphorus that is either present in the soil, or applied to the soil in the form of granular and liquid forms of fertiliser at the time of planting of most crops. The supplement comprises a composition selected from the group consisting of olivine, serpentine, and wollastonite, and can be activated by the addition of acid and/or heat. KR 2002/0070164 relates to a soil improving agent composition produced by adding olivine to sand and peat moss or an olivine powder impregnated solution or a composition containing the olivine in standard soil, wherein the olivine has a particle size of 0.01-5.0mm.

However, a composition comprising a combination of olivine and a fertilizing calcium salt according to claim 1 has heretofore not been described.

US 3,446,612 relates to a soil supplement composition for supplying magnesium and iron to a plant and to a method for promoting plant growth using the composition. The composition comprises olivine, ammonia and optional additives. US 3,446,612 fails to disclose a composition wherein the relative weight ratio between olivine and calcium salt is between 2:1 and 9:1. Moreover, since the olivine has been treated with sulfuric acid, the composition does not have any neutralizing power, let alone a neutralizing value of at least 25.

WOO 1/58831 discloses a soil supplement contains amorphous silica which reacts with water to form a mono silicic acid which can be absorbed by plants. Serpentine, wollastonite and olivine are mentioned as possible silicate materials. WO01/58831 is silent about adding fertilizing calcium salts. As in US 3,446,612, the silicate materials in WO01/58831 are treated with an acidic solution, preferably concentrated sulfuric acid.

US2002/0015988 relates to a granular formulation comprising a particulate substrate coated with a polymer layer containing microorganisms. Olivine is merely mentioned as one of the many possible substrates. No mention is made of neutralizing value or fertiziling calcium salts in de ratio of claim 1.

WO2010/050808, belonging to the fictious state of the art, relates to a method for making soil suitable for plant growth, comprising the introduction of a mycorrhizal fungus and a silicate rock onto or into the soil. Exemplary types of silicate rock include olivine. WO2010/050808 is silent about adding calcium salts and does not disclose a composition wherein the relative weight ratio between olivine and calcium salt is between 2:1 and 9:1. Olivine is vulnerable to chemical weathering; the tetrahedra of the olivine crystal structure allow olivine to be dissolved by acidic ground water and rainwater. Dissolution of the silicate tetrahedral releases the Fe²⁺ and Mg²⁺ ions. The weathering reaction is as follows:

Mg₂Si0₄ + 4 C0₂ + 4 H₂0 -» 2 Mg²⁺ + 4 HC0₃ + H₄Si0₄°

Thus, upon reaction with water (e.g. present in the soil) the complex silicates of olivine are converted to magnesium, silica and the bicarbonate ion which can raise the pH of acidic soil. Ultimately, this is followed by precipitation of bicarbonate ion to limestone (CaCOa) and dolomite (MgCOa). The use of olivine as C0₂ sequestering or capturing agent in a process called mineral carbonation is known in the art. Mineral sequestration aims to trap carbon in the form of solid carbonate salts. Carbonic acid in groundwater slowly reacts with complex silicates to dissolve calcium, magnesium, alkalis and silica and leave a residue of clay minerals. The dissolved calcium and magnesium react with bicarbonate to precipitate calcium and magnesium carbonates. One proposed reaction is that of the olivine-rich rock dunite, or its hydrated equivalent serpentinite with carbon dioxide to form the carbonate mineral magnesite, plus silica and iron oxide (magnetite) .

Mg-Olivine + Carbon dioxide→ Magnesite + Silica

Mg₂Si0₄ + 2C0₂→ 2MgC0₃ + Si0₂ + H₂0

The presence of the unique combination of olivine and at least one fertilizing calcium salt in a composition of the invention allows for its use in controlling the pH of the soil and supplementing plants with calcium without contributing to carbon dioxide emission. What is more, the C0₂-capturing activity of olivine makes it a highly attractive and sustainable neutralizing agent. Simultaneous application of a neutralizing agent, calcium and fertilizer makes it possible to avoid traditional liming based on calcium carbonate and in this way reduces the number of runs of technical equipment across the field. Also in view of the availability of olivine worldwide, the inventors herewith provide an

economically feasible and environmentally friendly alternative for

conventional agricultural liming materials. The olivine may be present in any suitable form. In general, a reduction in the grain size causes a relative increase of the surface area and therewith the wearing rate. The smaller the particle size the quicker the material will dissolve and react with the acid in the soil, so it is more effective than coarser material. Thus, a smaller grain size will enhance the rate at which the silicate complex is converted to the useful compounds (magnesium, bicarbonate). In one embodiment, olivine is present in a powdered form. Simple grinding procedures may be used to obtain the olivine powder. The particle size may range from about 5 to 250 μηι, like 5 to 200 or 10 to 100 μηι. However, smaller and/or larger particles may also be used. The powdered olivine is practically always polydisperse, which means that the particles in an ensemble have different sizes. It is preferred that at least 50%, more preferably at least 70% of the particles has a particle size from about 5 to about 100 μηι

The relative ability of a composition to counteract the effects of soil acidity can be expressed as an index, the neutralizing value (NV). Typically, and also as used herein, the neutralizing value is defined by the number of milliliters (mL) of a 0.357 molar solution of HC1 that can be neutralized by the addition of 1 gram of the composition. A soil conditioning composition provided herein has a NV of at least 25, preferably at least 30, more preferably the NV is at least 40 or at least 45, for example 46, 47, 48 or 49. In one embodiment, the

neutralizing value is at least 50, like around 60 or even higher. As will be understood from the discussion of the prior art herein above, the olivine present in a composition of the invention has preferably not been subjected to any treatment which reduces or destroys its acid neutralizing power. More specifically, the olive has preferably not been treated with an acid, like sulphuric acid.

A composition comprises at least one calcium-bearing which can provide at least one plant (macro)nutrient, preferably selected from nitrogen (N), phosphorous (P), sulphur (S). A calcium-containing compound for use according to the invention may be any naturally occurring calcium salt , e.g. calcium sulphate, calcium phosphate, calcium hydroxyapatite and their hydrates, or a mixture thereof. Inorganic and/or organic calcium salts can be used. Other useful calcium salts, or complexes like e.g. calcium alginate, calcium-EDTA and the like or organic compounds containing calcium like e.g. D-Glucaric acid calcium Salt (1:1), tetrahydrate, calcium organophosphates or bone meal. Any naturally occurring calcium salt(s) may be used in a composition of the invention, provided that its/their

decomposition/solubilisation results in ions that are not harmful or otherwise undesirable for plants or other living organisms. In view of the foregoing, the use of calcium carbonate is to be avoided. Inorganic and/or organic calcium salts can be used. Suitable calcium salts for use in combination with olivine are calcium ammonium nitrate, calcium sulphate (CaS04), calcium

phosphates, and their hydrates, or a mixture thereof. Also of use are organic calcium salts such as calcium salts of an organic acid. Appropriate calcium organic salts used in the compositions of the invention preferably have calcium ion contents of above 5 or even 10 percent. They include for example calcium glucoheptonate, calcium ascorbate, calcium gluconate, calcium lactate, calcium gluconolactate, calcium citrate, calcium fumarate and calcium levulinate.

The main sources of calcium sulphate are naturally occurring gypsum and anhydrite which occur at many locations worldwide as evaporites. These may be extracted by open-cast quarrying or by deep mining. World production of natural gypsum is around 127 million tonnes per annum. In addition to natural sources, calcium sulphate is produced as a by-product in a number of processes, including flue gas desulfurization, the production of phosphoric acid from phosphate rock, wherein calcium phosphate is treated with sulphuric acid and calcium sulphate precipitates, in the production of hydrogen fluoride, and in the refining of zinc. Calcium sulphate can also be recovered and re-used from scrap drywall at construction sites. In a preferred embodiment, the dihydrated form of calcium sulphate CaS04.2H20 (which occurs naturally as gypsum) is used.

In a preferred embodiment, at least one calcium phosphate is present. Calcium phosphate refers to a family of minerals containing calcium ions (Ca²⁺) together with orthophosphates (PO4³ ), metaphosphates or

pyrophosphates (P2O7⁴ ) and occasionally hydrogen

orhttp://en.wikipedia.org/wiki/Hydroxide hydroxide ions. Calcium phosphate compounds include calcium dihydrogen phosphate, E341(i): Ca(H2P04)2;

calcium hydrogen phosphate, E341(ii): CaHPC^ and tricalcium phosphate (or tricalcic phosphate), E341(iii): Ca3(P04)2. Also of use for the present invention is a naturally occurring form of calcium apatite with the formula

Ca5(P04)3(OH), which is usually written Caio(P04)6(OH)2 to denote that the crystal unit cell comprises two molecules. Some fertilizing calcium salts, such as calcium sulphate and calcium phosphates, are poorly soluble or insoluble in water. Thus, if these salts are applied the availability of the nutrient cations and anions to the plants is only low. The present inventors succeeded to increase the fertilizing effect of a composition of the invention comprising an insoluble calcium salt by supplementing the composition with at least one micro-organism capable of solubilising the calcium salt. Accordingly, the invention also relates to a composition comprising olivine and at least one fertilizing calcium salt that is poorly soluble or insoluble in water, and wherein the composition further comprises one or more micro-organisms capable of solubilising the at least one calcium salt, such that the calcium ions and fertilizing compounds are released to become accessible for plants. Suitable micro-organisms include bacteria, preferably spore forming bacteria, and fungi. . The relative weight ratio between olivine and the total amount of said calcium salt is preferably between 2:1 and 9:1, like between 3:1 and 5:1, most preferably about 4:1.

In a preferred embodiment, the micro-organism is capable of solubilizing insoluble forms of mineral phosphates for instance (tri)calcium phosphate and/or other salts. Preferably, a composition comprises (Ca)3(P04)2 in combination with one or more micro-organisms capable of solubilising

(tri)calcium phosphate.

Micro-organisms for practicing the invention can be found in the art, or they can be isolated from natural sources using established screening methods. For example, Chen et al. (2006, Applied Soil Ecology 34, pp. 33-41) disclose the screening and characterization of 36 strains of phosphate solubilizing bacteria (PSB). Described is the ability of a few soil microorganisms to convert insoluble forms of phosphorus to an accessible form. Mineral phosphate solubilizing (MPS) activities of all isolates were tested on tricalcium phosphate medium by analyzing the soluble-P content after 72 h of incubation at 30°C. More specifically, serially diluted soil samples were plated on standard agar medium (pH 6.8-7.0) containing 5 g of the salt tricalcium phosphate (TCP) as sole phosphorus source, for selectively screening the bacteria which have the ability to release inorganic phosphate from tricalcium phosphate (Nautiyal et al., 2000). Uninoculated plates and E. coli inoculated plates served as controls. After 3-days of incubation at 30°C, phosphate solubilizing bacteria developed clear zones around colonies. Colonies with clear zones were further purified by replating on agar medium supplemented with TCP. Thirty- six phosphate solubilizing bacterial strains thus screened were selected for further analysis. Identification and phylogenetic analysis of the isolates were carried out by 16S rDNA sequencing. The published method can be readily adapted to identify and isolate a micro-organism capable of solubilising other calcium salt(s) of interest, such as calcium sulphate.

In one embodiment, an isolate belonging to the genus Bacillus, the genus Rhodococcus, the genus Arthrobacter, the genus Serratia and the genera Chryseobacterium, Delftia, Gordonia or Phyllobacterium being able to solubilize tricalcium phosphate and/or calcium sulphate is used. In a specific aspect, a strain of Arthrobacter ureafaciens, Phyllobacterium myrsinacearum, Rhodococcus erythropolis or Delftia sp. is used. As will be understood, the use a mixture of two or more mineral solubilising strains is also envisaged.

In a preferred embodiment, a composition comprises olivine, at least calcium phosphate, e.g. tricalcium phosphate, and at least one mineral phosphate solubilising bacterium. In a specific aspect, a composition comprises an isolate belonging to the genus Bacillus, preferably Bacillus pumilis, Bacillus smithii, Bacillus coagulans and/or Bacillus licheniformis.

The amount of micro-organism present in a soil supplement of the invention can vary and will typically depend on various factors, such as the solubilising capacity, the type of salt(s) present, the characteristics of the soil and/or plants to be treated.

Generally speaking, the solubilising micro-organism is present in an amount of about 10exp3 to 10expl2 cfu (colony forming units) per gram of composition.

For ease of application, the composition is advantageously in the form of a granulated or pellitised composition. For example, the composition is in a particulate form. A typical granule size range can be between 0.1 and 10 mm, preferably 0.5 to 7 mm. Also here, the composition may be polydisperse.

A further aspect relates to a soil supplement composition as described above, which is presented in a suitable container, like a flexible or rigid (transparent) plastic package. Cardboard containers, like boxes, are also envisaged. The container may be provided with instructions for use as soil fertilizer and/or liming agent. The instructions are preferably placed on the exterior of the container and/or as a separate leaflet placed inside the container. The container may contain information about the carbon dioxide capturing capacity of the composition.

A composition of the invention is readily prepared by mixing together the different components in the desired relative proportions. It may involve the grinding of olivine and/or the preparation of particles or pellets by methods known in the art. Accordingly, also provided herein is a method for providing a soil conditioning composition, comprising mixing together the ingredients (olivine and one or more of the calcium salts) in the desired amounts in an aqueous slurry followed by removing water to obtain an essentially solid composition. In one embodiment, the components are mixed in a rotary granulator/dryer.The microorganism(s) can suitably be added by spraying onto the (partially) dehydrated product. Other additives may be present as well to improve the pellet stability and/or degradation.

Also provided is the use of a composition comprising olivine and at least one fertilizing occurring calcium salt, optionally in combination with at least one micro-organism capable of solubilizing the calcium salt, as a fertilizing soil conditioner. The term "fertilizing soil conditioner" as used herein refers to any application to a soil which improves at least one soil characteristic that enhances or supports plant growth. Preferred characteristics include pH, degree water penetration, calcium content, nutrient content such as nitrogen, potassium, phosphate and/or sulphate content.

A further embodiment relates to a method for promoting the growth of a plant, comprising contacting an effective amount of a soil supplement composition according to the invention with at least part of the soil wherein said plant is present or will be present. The effective amount will depend on various factors that are known to the skilled person. Relevant factors include pH of the soil, calcium need of the plant, temperature, humidity, olivine grain size, olivine composition, and the like. Also provided is a method for neutralizing soil acidity, comprising contacting soil with a composition of the invention.

Maximum contact with the soil in the cultivated layer is desirable. The skilled person will be able to determine how much of the composition is to be used. Typically, the supplement is added in an amount of 0.1 to 10 kg, preferably 0.5 to 2 kg per 10 square meters of soil. For example, it is applied at 1 kg/10 m². The time and frequency of application also depend on the circumstances. In rotations that include a crop requiring the soil pH to be raised, the composition may be applied 3-6 months ahead of planting the crop, especially on very acid soil, to allow enough time for the olivine to react in the soil. General statements concerning the frequency of application are difficult to provide because so many factors are involved. A good way to determine when to (re-) apply is by a soil test. The following factors will influence the frequency of application: soil texture, rate and/or type of N fertilization (high rates of ammonium-nitrogen generate considerable acidity), rate of crop removal, amount of composition applied and the pH range desired. Soil tests can be used to monitor pH changes with time.

The invention is illustrated by the following non-limiting examples. EXAMPLE 1

This example describes the production of a soil supplement according to the invention in a pelleted form. Materials used: olivine powder (5-80 μηι average diameter); calcium phosphate, suspension of Bacillus isolate. 1. The olivine and calcium phosphate are mixed in the desired weight ratio and water is added to obtain a slurry.

2. This slurry is homogenized and later on pressed through a special filtration, so most of the water is separated.

3. The partially dried dryer slurry is granulated in a large plate to pellets 4. The pellets are dried at 200 °C.

5. After cooling the temperature of the pellets down to about 30 °C, the microorganisms are sprayed onto the pellets.

6. The microorganisms are absorbed by the pellets during the transport via conveyor to the storage bunker. EXAMPLE 2

This example demonstrates the neutralizing value of three exemplary soil supplements of the invention as compared to a commercially available traditional (CaC03-based) soil supplement known as "kalk". As a further reference, olivine alone was analyzed. Neutralizing values were determined according to well established methods. Briefly, an aqueous suspension of the test sample is boiled in the presence of a known and excess amount of titrated HCl. Samples comprising organic matter are priorly ashed. Samples containing more than 3% P2O5 are pretreated to precipitate phosphates with a 1% (w/v) solution of ferriacetate (Fe(HI)(CH₃COO)₃).

The amount of alkaline constituents in the suspension is assessed by back titration of the excess acid. The neutralizing value (NV) is expressed by the number of milliliters of a 0.357 molar solution of HCl can be neutralized by the addition of 1 gram of the composition.

Results are shown in Table 1.

Test sample Neutralizing value

Kalk (reference) 52

Olivine (reference) 60

01ivine/CaS0₄ 80:20 w/w 50

01ivine/CaS0₄ 50:50 w/w 34

Olivine/CaaiPO*)?. 75:25 w/w + Bacillus 48

Claims

1. A soil supplement composition comprising olivine and at least one fertilizing calcium salt, wherein the relative weight ratio between said olivine and the total amount of said calcium salt is between 2:1 and 9:1 and wherein the composition has a relative neutralizing value of at least 25.

2. Composition according to claim 1, wherein said relative weight ratio is between 3:1 and 5:1, preferably about 4:1.

3. Composition according to claim 1 or 2, having a relative neutralizing value of at least 30, preferably at least 40.

4. Composition according to any one of the preceding claims, wherein the calcium salt is selected from the group consisting of calcium ammonium nitrate, calcium sulphate, calcium phosphate, their hydrates, calcium salts of organic acids, and any combination thereof.

5. Composition according to claim 4, comprising (Ca)3(P04)2.

6. Composition according to any one of the preceding claims, further comprising at least one micro-organism capable of solubilizing the at least one calcium salt.

7. Composition according to claim 6, comprising at least one microorganism capable of solubilizing calcium phosphates.

8. Composition according to claim 6 or 7, comprising at least one micro- organism selected from the group consisting of the genus Bacillus, the genus

Rhodococcus, the genus Arthrobacter, the genus Serratia and the genera Chryseobacterium, Delftia, Gordonia and Phyllobacterium.

9. Composition according to any one of claims 6-8, wherein said microorganism is present in an amount of 10exp3 - 10expl2 cfu per gram of composition.

10. Composition according to any one of the preceding claims, wherein said olivine is present in a powdered form, preferably having a particle size between 5 and 250 μηι.

11. Composition according to any one of the preceding claims, wherein said composition is in particulate form, preferably having a particle size between 0.1 and 10 mm.

12. A container or kit comprising a composition according to any one of the preceding claims.

13. Container or kit according to claim 12, further comprising instructions for use of the composition as soil fertilizer and/or liming agent.

14. The use of a composition according to any one of claims 1 to 11 as a soil conditioner and/or fertilizer.

15. A method for promoting the growth of a plant, comprising contacting an effective amount of a soil supplement composition according to any one of claims 1 to 11 with at least part of the soil wherein said plant is present or will be present.