Description

Title of the invention: Use of an aluminosilicate glass to provide a plant with silicon in an assimilable form, process for treating a plant using this glass and new powder of said glass

Technical area

The present invention generally relates to the use of a specific aluminosilicate glass as a source of silicon to supply a plant with silicon in an assimilable form. It also relates to a process for treating a plant using this aluminosilicate glass. Finally, it relates, as a new product, to powders of this aluminosilicate glass.

The invention finds particular application in the agricultural field.

Prior technique

Silicon is an element favoring the good vegetative development of plants, such as Solanaceae, Astéereaceae, Poaceae and Sinapis Alabae. In general, silicon can only be assimilated by plants in the form of silicic acid. It is generally transported following the transpiration stream from the roots to the aerial organs where it is accumulated and precipitates to form biogenic opals called phytoliths.

Research carried out over several years has shown that absorbed silicon increases the productivity and quality of agricultural crops. In particular, silicon has been shown to improve drought tolerance and slow wilting in some plants when irrigation is delayed. It can also increase the strength of rice or wheat stalks, preventing them from collapsing in heavy rain or strong wind.

Given these advantages, research has been undertaken to develop compositions making it possible to supply silicon to a plant, in an assimilable form.

Thus, in document WO 2010/040176, it is proposed to use, as a source of silicon assimilable by the plant, particles of a soda-lime glass containing a content of at least 50% by weight of silica (Si0 ) and a content of at least 2% by weight of sodium oxide (Na20). However, to obtain a satisfactory effect, these particles must be very fine and have a median size generally less than 37 μm.

The process described in this prior document for the manufacture of these glass particles is relatively expensive to implement on an industrial scale, insofar as it requires prolonged grinding and the use of a confined space and specific means of protecting people to obtain and implement the targeted particles.

Furthermore, it has been observed that the particles of soda-lime silica glass in accordance with the teaching of this prior document release practically no silicon in the presence of the acids usually released by the plants and that the quantities of phytoliths formed in the plants treated by these soda-lime glass particles remain relatively low reflecting a limited assimilation of silicon.

In document FR 3051463, it has been shown that silicon stimulates the absorption of nitrogen, in particular in the form of urea, in the plant. Numerous sources of silicon are mentioned in this document such as in particular solid or liquid mineral forms, vitreous products or organic silicas. In the examples demonstrating the stimulation of nitrogen absorption, sodium silicate is used with an addition of nickel.

However, it has been observed that, despite an almost immediate dissolution in the presence of acids that can be generated by the soil, sodium silicate leads to a limited formation of phytoliths in plants, again translating a limited assimilation of silicon.

Disclosure of Invention

In this context, the present invention aims to solve the technical problem of providing a source of silicon which can be assimilated by plants and which leads to the formation of a large quantity of phytoliths, which can be obtained and used from a simple and inexpensive way on an industrial scale.

It has been discovered, and this constitutes the basis of the present invention, that specific aluminosilicate glasses, used in particular in the form of particles, are particularly effective in providing a plant with silicon in an assimilable form. It has been shown, in particular, that these glasses lead to the formation of high amounts of phytoliths, unlike the sources of silicon described in the state of the art. In addition, it has been observed that this supply of silicon can be obtained with particles of dimensions greater than those described in document WO 2010/040176, the production of which is consequently less costly on an industrial scale. Finally, these aluminosilicate particles can be formulated without difficulty in fertilizer compositions,

especially in the form of granules, making it particularly easy to use in agriculture.

Without being bound by a theoretical interpretation, the inventors believe that the improvement in the absorption of silicon in assimilable form, demonstrated by the presence of a large quantity of phytoliths in the plant, is the consequence of the ability of glass to aluminosilicate to dissolve congruently under the action of organic acids released by plants.

Thus, it has been observed that silica, although a structural constituent of glass, dissolves at the same time as the other constituents, in acidic media identical to the organic acids released by plants. As a result, the supply of silicon to plants is done in a progressive and controlled manner.

In addition, due to its particular composition, and in particular its high alumina content, this aluminosilicate glass does not dissolve or dissolves very little in an aqueous medium close to a neutral pH, which makes it possible to formulate it within fertilizer composition, in particular in the form of granules.

Thus, according to a first aspect, the subject of the present invention is the use of an aluminosilicate glass comprising the following constituents, in a content by weight varying within the limits defined below:

Si02 30-60%

Al203 10-26%

Ca0+Mg0+Na20+K20 15-45%

as a source of silicon, to provide a plant with silicon in an assimilable form.

According to a second aspect, the subject of the present invention is a process for treating a plant, characterized in that in order to provide this plant with silicon in an assimilable form, one applies to said plant, or to the growth medium of said plant, an aluminosilicate glass as defined in the following description.

According to a third aspect, the subject of the present invention is an aluminosilicate glass powder as defined above, said powder having a distribution of particle sizes such that the median diameter by volume of these particles "D50" is between 60 and 250 microns, preferably between 75 and 180 microns.

Definitions

In the context of this description, the following terms mean:

“plant”: the plant considered as a whole, including its root apparatus, its vegetative apparatus, grains, seeds and fruits;

particle “diameter”: the diameter of the equivalent sphere in volume of said particle;

"DX": is the value expressed in microns of the particle diameter such that, in a given sample of particles, and taking into account a particle size distribution by volume, X% of the distribution has a diameter less than this diameter DX; for example, in the case of a powder having a D90 equal to 300 microns, the particles having a diameter less than 300 microns occupy 90% of the total volume of the sample. In other words, in a cumulative volume distribution, the DX value corresponds to the diameter for which the cumulative function is X%; the particle size distribution by volume can be obtained in particular by laser diffraction;

“fertilizer”: any product or composition whose use is intended to ensure or improve the physical, chemical or biological properties of the soil as well as the nutrition of plants;

“fertilizer”: any fertilizing material whose main function is to provide plants with nutrients which may be major or secondary nutrients or trace elements;

“silicon accumulating plant”: any plant likely to contain more than 1% (weight/weight) of silicon relative to the dry mass of the plant and a Si/Ca molar ratio greater than 1.

General definition of an aluminosilicate glass within the meaning of the invention.

In general, the aluminosilicate glass used according to the invention comprises the following constituents, in a content by weight varying within the limits defined below:

Si02 30-60%

Al203 10-26%

Ca0+Mg0+Na20+K20 15-45%

K20 0-10%

Fe203 (total iron) 0-15%

P205 0-4%

Preferred contents according to the invention.

The Si0 content is preferably within a range ranging from 35 to 49%, in particular from 36 to 45%, or even from 38 to 44%.

The Al203 content is preferably within a range ranging from 12 to 25%, in particular from 14 to 24%, or even from 15 to 23%.

It has been found that an aluminosilicate glass having Si02 and Al203 contents falling within the general and preferred ranges defined above, has the advantageous property of being able to dissolve congruently under the action of organic acids released by plants. and thus release silicon directly assimilable by plants. It has also been found that such a glass does not dissolve or dissolves very little in aqueous media close to neutral pH, which is particularly advantageous from an industrial point of view insofar as this glass can be used without any particular constraint in the preparation of fertilizers, in particular in the form of granules.

The sum of CaO, MgO, Na20 and K20 contents (denoted Ca0+Mg0+Na20+K20) is preferably within a range ranging from 20 to 40%, in particular from 25 to 35%. The presence of these alkaline-earth and alkaline oxides facilitates the melting of the glass and also contributes favorably to the dissolution of the glass in contact with organic acids.

The CaO content is preferably within a range ranging from 8 to 30%, preferably from 10 to 30%, especially from 12 to 28%. The MgO content is preferably within a range ranging from 1 to 15%, in particular from 1 to 12%, or even from 1 to 11%.

The Na20 content is preferably within a range ranging from 0 to 12%, in particular from 1 to 10%. The K20 content is preferably within a range ranging from 0 to 8%, preferably from 1 to 8%, in particular from 1 to 7%, or even from 1 to less than 5%.

According to one embodiment, the sum of the CaO and MgO contents is included in a range from 25 to 40%, in particular from 27 to 35% and the sum of the Na20 and K20 contents is included in a range from 0 to 6%, in particular from 0 to 5%, or even from 1 to 5%.

According to another embodiment, the sum of the CaO and MgO contents is included in a range ranging from 10 to 25%, in particular from 12 to 20% and the sum of the Na20 and K20 contents is included in a range ranging from 8 to 15%, in particular from 9 to 13%.

The total content of iron oxide, expressed in the Fe203 form, is preferably within a range ranging from 0 to 13%, in particular from 2 to 12%, or even from 4 to 12%. The oxide of

iron can be present in the form of ferrous oxide FeO and/or ferric oxide Fe 0 . The redox, defined as being the ratio of the content of ferrous oxide, expressed in the form FeO, and the total molar content of iron oxide, expressed in the form Fe203, is preferably included in a range ranging from 0.1 to 0.9, in particular from 0.2 to 0.9.

Preferably, the total content of Si02, Al203, CaO, MgO, Na20, K20, and Fe203 is at least 94%, in particular at least 95% and even at least 96% or at least 97 %.

The P205 content is preferably less than or equal to 4%, in particular 3%, or even 2% and even 1%. It is advantageously at most 0.5% and even zero, except for unavoidable impurities.

The BaO content is preferably less than or equal to 5%, especially 4%, or even 3% and even 2% or 1%. It is advantageously at most 0.5% and even zero, except for unavoidable impurities.

The SrO content is preferably less than or equal to 5%, in particular 4%, or even 3% and even 2% or 1%. It is advantageously at most 0.5% and even zero, except for unavoidable impurities.

The ZnO content is preferably less than or equal to 5%, especially 4%, or even 3% and even 2% or 1%. It is advantageously at most 0.5% and even zero, except for unavoidable impurities.

The B203 content is preferably less than or equal to 5%, in particular 4%, or even 3% and even 2% or 1%. It is advantageously at most 0.5% and even zero, except for unavoidable impurities.

The Ti02 content is preferably less than or equal to 5%, especially 4%, or even 3% and even 2% or 1%.

The Zr02 content is preferably less than or equal to 5%, especially 4%, or even 3% and even 2% or 1%. It is advantageously at most 0.5% and even zero, except for unavoidable impurities.

Other components may be present in the chemical composition of the aluminosilicate glass used according to the invention, either deliberately or as impurities present in the raw materials or originating from the refractories of the furnace. It may be in particular SO3, resulting from the addition of sodium or calcium sulphate as a glass refiner.

It goes without saying that the different preferred ranges described above can be freely combined with each other, the different combinations not being able to all be listed for reasons of conciseness.

Some preferred combinations are described below.

According to a preferred embodiment, the aluminosilicate glass used according to the invention has a chemical composition comprising the following constituents, in a content by weight varying within the limits defined below:

Si02 35-49%

Al203 12-24%

Ca0+Mg0+Na20+K20 20-40%

Fe203 0-12%.

According to a particularly preferred embodiment, this glass has a chemical composition comprising the following constituents, in a content by weight varying within the limits defined below:

Si02 36-45%

Al203 14-23%

Ca0+Mg0+Na20+K20 25-35%

Fe203 0-10%.

The various preferred ranges listed above concerning the other oxides are of course applicable to these preferred modes. In particular, the P205 content is preferably less than or equal to 4%, in particular 3%, the BaO content is preferably less than or equal to 5%, in particular 4%, the SrO content is preferably less than or equal to equal to 5%, in particular 4%, the ZnO content is preferably less than or equal to 5%, in particular 4%, the B203 content is preferably less than or equal to 5%, in particular 4%, the Ti02 content is preferably less than or equal to 5%, in particular 4%, the Zr02 content is preferably less than or equal to 5 %, notably at 4%.

The aluminosilicate glass used according to the invention can be manufactured by all known melting methods. A vitrifiable mixture containing natural and/or artificial raw materials is brought to a temperature of at least 1300° C., in particular between 1400 and 1600° C. in order to obtain a mass of molten glass. The raw materials are chosen in particular from silica sand, feldspars, basalt, bauxite, blast furnace slags, nepheline, nepheline syenite, limestone, dolomite, phonolite, sodium carbonate, carbonate potassium, iron oxide, gypsum, sulphate of

sodium, calcium phosphate. The vitrifiable mixture is in particular heated in a glass furnace, by means of flames issuing from overhead or submerged burners and/or electrodes, or in a cupola, thanks to the combustion of coke.

The aluminosilicate glass is obtained after cooling the vitrified mixture thus prepared.

In the context of the present invention, the aluminosilicate glass defined above is preferably used in the form of particles, in particular particles having a distribution of sizes such that the median diameter by volume of these particles "D50" is between 60 and 250 microns, preferably between 75 and 180 microns.

Advantageously, these particles will also have a D90 value of between 150 and 600 microns, preferably between 150 and 350 microns, more preferably between 150 and 300 microns.

Advantageously, these particles will also have a D10 value of between 10 and 40 microns, preferably between 15 and 30 microns.

These particles may be obtained by grinding the glass prepared as indicated above, for example by means of a pendular mill associated with an aerodynamic selector, or even a ball mill. These particles can also be obtained by grinding glass fibers.

The aluminosilicate glass which has just been described can be used advantageously in a process for treating a plant consisting in applying to said plant an effective quantity of said glass. Advantageously, this process will be applied to a plant in suboptimal nitrogen conditions as will be understood in the remainder of this description.

Plants have an absolute need for nitrogen. Indeed, nitrogen is the pivot of their growth and a determining nutrient element of the yield because it constitutes the main factor limiting the development of the plant. Therefore, crop growth, yield and quality depend on substantial nitrogen inputs.

Today, the use of nitrogen in agriculture represents more than 80 million tons per year worldwide, and crop production must continue to grow with the growing demand of the world's population. However, the increasing use of nitrogen in agriculture poses ecological problems. Therefore, improving yields, while preserving the environment through sustainable agricultural production, represents a major challenge for today's agriculture.

The use of fertilizers specifically developed to better meet the nitrogen needs of plants has made it possible to considerably improve agricultural production. However, these fertilizers are expensive to produce and their use can be environmentally problematic due to losses to the environment of excess nitrogen that is not properly assimilated by the plant. It is therefore absolutely necessary to maximize the efficiency of nitrogen fertilizer use. This efficiency corresponds to the relationship between production (yield) and the units of fertilizer applied. It depends on several complex processes linked to the development of the plant, the variety (genetic factor) and the environmental conditions (climate, nature of the soil, etc.).

Although the application of more nitrogen results in increased yields, it is not a linear relationship. Indeed, there is a so-called "optimal" dose to be applied which makes it possible to achieve an optimal yield, that is to say beyond which the yield no longer increases, so that the excess nitrogen will be lost to the environment. This results in poor nitrogen efficiency.

As shown in Figure 1, as an example in the case of wheat {Triticum aestivum), a low nitrogen supply of 48, 96 or 144 Kg N. ha 1 year 1 results in stunted growth and therefore low yields. On the other hand, nitrogen losses are low. An optimal nitrogen supply of 192 Kg N. ha 1 year 1 or an excess of nitrogen (quantities greater than 192 Kg N. ha 1 year 1) leads to high yields, but is accompanied by high nitrogen losses and low nitrogen efficiency.

Thus, in order to limit nitrogen losses to the environment, and reduce the impact of fertilization on the environment, while generating a financial gain, it is essential to achieve optimum yield with a nitrogen supply. (nitrogen inputs) in a quantity lower than the optimal quantity.

In this context, the method in accordance with the invention is particularly advantageous since it has been demonstrated that the use of the aforementioned aluminosilicate glass makes it possible to increase the yield under suboptimal conditions of nitrogen supply, up to a level close to or even identical to the level obtained under optimal nitrogen supply conditions, thus perfectly meeting the growth needs of the crop.

In the context of the present description, by the expression “suboptimal dose of nitrogen” is meant a dose corresponding to a reduction of at least 20%, preferably of at least 30% of the optimal dose calculated to reach the optimum performance.

The optimal dose of nitrogen needed to maximize production is calculated based on the needs of the plant. As shown in Table 1, these requirements may vary depending on the variety and the pedoclimatic conditions.

Table 1

Thus, by making it possible to reduce the doses of nitrogen applied while maintaining yields at their optimum level, the treatment method according to the invention provides a response to the undesirable effects on the ecological level of fertilization by nitrates (problem of leaching ) or by urea (problem of volatilization).

In a particular embodiment, the treated plant is chosen from rice, grassland, rapeseed, sunflower, wheat, oats, sugar cane, barley, soybean, corn, preferably meadow.

The aluminosilicate glass used according to the invention therefore acts as a stimulant of growth and yield mechanisms, in particular under suboptimal nitrogen supply conditions, in a plant. The present invention thus covers the use of an aluminosilicate glass as defined previously for increasing the yield under suboptimal nitrogen conditions in a plant.

Within the meaning of the invention, the term "stimulator of the yield under suboptimal conditions of nitrogen supply" means the activity allowing an increased increase of at least 10% in the yield under conditions of low nitrogenous inputs.

The aluminosilicate glass used according to the invention also acts as a nitrogen efficiency stimulant, in particular under suboptimal nitrogen supply conditions, in a plant. The present invention thus also covers the use of an aluminosilicate glass as defined above for increasing the nitrogen efficiency under suboptimal nitrogen conditions in a plant.

Within the meaning of the invention, the term “stimulating nitrogen efficiency under suboptimal conditions of nitrogen supply” means the activity allowing an increased increase of at least 10% in nitrogen efficiency under conditions of low nitrogen inputs. .

In the method of the invention, an effective amount of an aluminosilicate glass is supplied to the plant to boost yield and nitrogen efficiency under suboptimal nitrogen conditions. By the expression "effective amount" is meant an amount making it possible to increase the yield and the nitrogenous efficiency of a plant under suboptimal conditions of nitrogen supply, by at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, advantageously at least 30%, at least 35%, at least 40%, at least 45%, advantageously at least 50%, at least 55%.

The increase in yield is measured by determining the biomass produced by the plant. The term "increase" refers to the plant having received no contribution from an aluminosilicate glass.

The increase in nitrogen efficiency is measured by determining the ratio between the yield and the amount of nitrogen supplied to the plant. The term "increase" refers to the plant having received no contribution from an aluminosilicate glass.

In the process for treating a plant according to the invention, the aluminosilicate glass is advantageously supplied to the plant by the root route.

This treatment can in particular be applied in fields but also in greenhouses, possibly in soilless culture substrates.

In a particular embodiment, the aluminosilicate glass is supplied to the plant in an amount ranging from 2 kg/ha (kilograms/hectare) to 1000 kg/ha. In this embodiment, the aluminosilicate glass is advantageously spread evenly over a field or crop of plants.

In another particular embodiment, the aluminosilicate glass is supplied to the plant in solid form within powder/pulverulent or granular fertilizers, preferably in an amount ranging from 5 to 800 kg/tonne of fertilizer (T ) and preferably of the order of 50 to 300 kg/tonne of fertilizer (T).

The glass of The aluminosilicate can thus be used as a supplement in fertilizing compositions, such as fertilizers, as a stimulant of the yield and of the nitrogenous efficiency under suboptimal conditions of nitrogen supply in a plant. This glass can in particular be combined with other fertilizing substances conventionally used in fertilizing compositions.

In a particular embodiment of the invention, an effective amount of an aluminosilicate glass is used in a fertilizing composition in combination with one or more fertilizing substances. The fertilizing substances likely to be used in combination with the aluminosilicate glass can be of various natures and chosen, for example, from urea, a nitrogenous solution, ammonium sulphate, ammonium nitrate, natural phosphate, potassium chloride, ammonium sulphate, magnesium nitrate, manganese nitrate, zinc nitrate, copper nitrate, phosphoric acid, boric acid. Advantageously, this additional fertilizing substance is chosen from urea, ammonium sulphate, ammonium nitrate, a nitrogenous solution and/or potassium nitrate.

The invention also relates to a method for stimulating the yield and the nitrogen efficiency under suboptimal conditions of nitrogen supply in a plant, characterized in that it comprises the supply to the said plant or to the soils, of an effective quantity aluminosilicate glass as defined above.

Claims

[Claim 1] Use of an aluminosilicate glass comprising the following constituents, in a content by weight varying within the limits defined below:

Si02 30-60%

Al203 10-26%

Ca0+Mg0+Na20+K20 15-45%

as a source of silicon, to provide a plant with silicon in an assimilable form.

[Claim 2] Use according to Claim 1, characterized in that in the said aluminosilicate glass the content by weight of Si02 is between 35 and 49%, preferably between 36 and 45% and more preferably between 38 and 44%.

[Claim 3] Use according to Claim 1 or 2, characterized in that in the said aluminosilicate glass the content by weight of Al203 is between 12 and 25%, preferably between 14 and 24%, more preferably between 15 and 23 %.

[Claim 4] Use according to any one of Claims 1 to 3, characterized in that in the said aluminosilicate glass the cumulative content by weight of CaO, MgO, Na20 and K20 is between 20 and 40%, preferably between 25 and 35%.

[Claim 5] Use according to any one of Claims 1 to 4, characterized in that in the said aluminosilicate glass:

- the weight content of CaO is between 8 and 30%, preferably between 12 and 28%; and

- the content by weight of MgO is between 1 and 15%, preferably between 1 and 12%.

[Claim 6] Use according to any one of Claims 1 to 5, characterized in that in the said aluminosilicate glass:

- the content by weight of Na20 is between 0 and 12%, preferably between 1 and 10%;

- the content by weight of K20 is between 0 and 8%, preferably between 1 and 7%, more preferably between 1 and 5%.

[Claim 7] Use according to any one of Claims 1 to 6, characterized in that in the said aluminosilicate glass:

- the sum of the contents by weight of CaO and MgO is between 25 and 40%, preferably between 27 and 35%; and

- the sum of the contents by weight of Na 0 and K20 is between 0 and 6%, preferably between 0 and 5%, preferably between 1 and 5%.

[Claim 8] Use according to any one of Claims 1 to 6, characterized in that in the said aluminosilicate glass:

- the sum of the contents by weight of CaO and MgO is between 10 and 25%, preferably between 12 and 20%; and

- the sum of the contents by weight of Na20 and K20 is between 8 and 15%, preferably between 9 and 13%.

[Claim 9] Use according to any one of Claims 1 to 8, characterized in that the said aluminosilicate glass contains iron oxide and in that:

- the total content by weight of iron oxide, expressed in the Fe203 form, is between 0 and 13%, preferably between 2 and 12%, more preferably between 4 and 12%.

[Claim 10] Use according to any one of claims 1 to 9, characterized in that in said aluminosilicate glass, the total content by weight of Si02, Al203, CaO, MgO, Na20, K20 and Fe203 is at least 94%, preferably at least 95% and more preferably at least 97%.

[Claim 11] Use according to any one of claims 1 to 10, characterized in that said aluminosilicate glass comprises the following constituents, in a content by weight varying within the limits defined below:

Si02 35-49%

Al203 12-24%

Ca0+Mg0+Na20+K20 20-40%

Fe203 0-12%.

[Claim 12] Use according to Claim 11, characterized in that the said aluminosilicate glass comprises the following constituents, in a content by weight varying within the limits defined below:

Si02 36-45%

Al203 14-23%

Ca0+Mg0+Na20+K20 25-35%

Fe203 0-10%.

[Claim 13] Use according to any one of Claims 1 to 12, characterized in that the said aluminosilicate glass is in the form of particles having a distribution of sizes such that the median diameter by volume of the particles "D50" is between 60 and 250 microns, preferably between 75 and 180 microns.

[Claim 14] Process for treating a plant, characterized in that in order to provide this plant with silicon in assimilable form, said plant or the growth medium of said plant is applied to an aluminosilicate glass such as defined with reference to any one of claims 1 to 13.

[Claim 15] Method of treatment according to Claim 14, characterized in that the aforesaid plant is in a suboptimal nitrogen condition.

[Claim 16] Process according to claim 14 or 15, characterized in that the aforementioned plant is chosen from rice, grassland, rapeseed, sunflower, wheat, oats, sugar cane, barley, soy, corn.

[Claim 17] Treatment process according to any one of Claims 14 to 16, characterized in that the aluminosilicate glass is supplied to the plant in an amount of between 20 and 500 kg/T, preferably between 50 and 300 kg/T, preferably in solid form, more preferably in a fertilizer composition in powder or granular form.

[Claim 18] Treatment process according to any one of Claims 14 to 17, characterized in that the said aluminosilicate glass is supplied by the root route.

[Claim 19] Aluminosilicate glass powder, characterized in that:

- said glass is as defined with reference to any one of claims 1 to 13; and

- said powder has a particle size distribution such that the volume median diameter of these "D50" particles is between 60 and 250 microns, preferably between 75 and 180 microns.

[Claim 20] Fertilizer composition, characterized in that it contains at least one source of nitrogen mixed with at least one aluminosilicate glass as defined with reference to any one of Claims 1 to 13.