STIMULATION OF SOIL NITRIFICATION WITH COMPOSITIONS CONTAINING A PLANT EXTRACT

Description

Technical field

[0001] The invention finds its application in the agro-ecological and agricultural field and relates in particular to the stimulation of the nitrification of a soil with compositions comprising a plant extract. Technological background

[0002] Nitrogen fertilization plays a vital role in crop growth and yield. Nitrogen is the main component of amino acids and proteins, making it a critical element for plant growth and quality. As it undergoes a natural cycle in the air, soil, and water, nitrogen undergoes various chemical and biological transformations—the nitrogen cycle.

[0003] The global nitrogen cycle describes the transformations of gaseous nitrogen, mineral nitrogen, and nitrogen-rich organic compounds present on Earth. It is a set of microbial processes controlled by soil microorganisms. This includes assimilation, ammonification, nitrification, denitrification, biological nitrogen fixation, and anaerobic ammonia oxidation.

[0004] Among all these processes, nitrification is the most important biological step in the nitrogen cycle in soil, and it is considered a limiting step that can be the cause of low nitrogen use efficiency, which can contribute to groundwater pollution and greenhouse gas emissions (N 2 O). The nitrification rate can vary depending on the nature of the soil. Factors regulating the nitrification process include soil pH, temperature, humidity, nitrogen fertilizer applied to the soil, microorganisms, and the physical nature of the soil.

[0005] Nitrification is the oxidation of ammonium (NH 4 +< ) into nitrate (NO 3 -< ). This nitrification occurs in several stages. First, bacteria and archaea of ​​the Nitrosomas group, AOB (Ammonia-Oxidising Bacteria) and AOA (Ammonia-Oxidising archaea), oxidize ammonium into hydroxylamine (NH 2 OH). The latter is taken over by Nitrite-Oxidising Bacteria (NOB) to transform it into nitrite (NO 2 -< ). Finally, Nitrobacter oxidizes nitrites into nitrate (NO 3 -< ). In order to transform ammonium into nitrites, four protons are released as well as two water molecules; this phenomenon causes acidification of the soil, particularly around the roots. The activity of AOB and AOA bacteria is highly dependent on the environment, especially humidity, pH, temperature and ammonium availability have a great influence.

[0006] Nitrogen exists in different forms: in the free state as N2, where it constitutes 78% of the air, and in the combined state, in mineral or organic form. Organic nitrogen

[0007] Soil nitrogen reserves are found in the organic form of humus or SOM (Soil Organic Matter), originating from crop residues or animal droppings. It is made up of various nitrogen compounds (proteins, amino acids, etc.), and whose mineralization is highly variable and difficult to predict. Mineral nitrogen

[0008] It comes from the decomposition of organic matter by soil flora and fauna (mineralization process), or directly from the application of inorganic fertilizers. Mineral nitrogen is composed of three main forms: urea, ammonium, and nitrates.

[0009] Urea is a widely used source of nitrogen worldwide. Although it can be directly absorbed by plants, it is most often hydrolyzed to ammonium (NH 4 +< ), a form more easily assimilated by plants. This transformation is accompanied by an increase in soil pH and significant losses by volatilization (NH 3 : gaseous ammonia), which cause atmospheric pollution. Strict urea nutrition can lead to reduced growth and sometimes even the appearance of nitrogen deficiency.

[0010] Ammonium is one of the main sources of nitrogen for plants. At high concentrations, this element can be toxic to plants when it accumulates in tissues. Ammonium can be supplied in the form of fertilizers. Thanks to its positive charge, NH 4 +< binds to the clay-humic complex of the soil, which limits its instantaneous availability to the plant. Since ammonium is fixed by the soil, it cannot move within it. Absorption by the plant can therefore only take place in an area close to the root zone. The ions fixed between the clay layers are mostly oxidized by nitrifying bacteria (Nitrobacter, Nitrosomas, etc.) and transformed into nitrates; this is the nitrification process, which is accompanied by a decrease in soil pH.

[0011] Nitrate is considered the major and preferred source of nitrogen for plants. Furthermore, the mobility of nitrate in the soil facilitates its absorption by plants. Therefore, most plants exhibit a nitrophilic nature. Nitrate, carrying a negative charge, is not retained by soil particles and, therefore, can be easily leached due to its solubility. It can also be reduced to nitrogen oxide gas through the process of denitrification. Furthermore, due to its solubility, nitrate is easily transported by soil water to the roots; this is the phenomenon of mass flow.

[0012] The nutritional value of each form of nitrogen varies from one form to another. In order of preference, plants primarily absorb nitrate (NO 3 -< ), then ammonium (NH 4 +< ), and to a lesser extent urea.

[0013] Plants grown on mixed nitrogen sources containing nitrate and urea or nitrate and ammonium, or on sources containing all three forms of nitrogen (urea, ammonium, and nitrate), exhibit better growth than plants grown on urea or ammonium alone.

[0014] Controlling the nitrification process and the transition from the ammoniacal form to the nitric form, to have both forms (ammonium and nitrate, or urea and nitrate) or all three forms (urea, ammonium and nitrate) is crucial to improve the efficiency of nitrogen use by plants, helping to increase yields while preserving the environment.

[0015] The rate of nitrification in soil has a significant impact on the availability of various forms of mineral nitrogen, primarily nitrate, to plants. The rate of nitrification depends on several parameters such as moisture, pH, temperature, and ammonium availability. Acidic soil pH, low humidity, and cold temperatures decrease the rate of nitrification. Alkaline soil pH, high humidity, and warm temperatures increase the rate of nitrification.

[0016] Several types of nitrogen fertilizers are marketed, for example: Ammonium sulfate, which, crystallized or granulated, gives a fertilizer called ammonium sulfate often dosed up to 21% nitrogen. Urea obtained by combining ammonia and carbon dioxide formed during the synthesis of ammonia. Urea is a molecule widely present in the natural environment. It is a source of nitrogen for the growth of various organisms including bacteria, fungi and plants. Due to its high nitrogen content (46%) and its low production cost, urea represents more than 50% of the total nitrogen fertilizers used in agriculture. Ammonium nitrate obtained by reaction between ammonia and nitric acid. This form doses 27%; 33.5% or 35% of total nitrogen. It is composed of 50% nitrogen in the form of ammonium and 50% in the form of nitrate and it is the most used product in France and Europe. Nitrate and ammonium are the main sources of nitrogen for plant growth.The nitrogen solution contains 30% nitrogen by mass and 39% by volume. This type of fertilizer contains all three forms of nitrogen: 50% urea, 25% ammonia, and 25% nitrate.

[0017] There is therefore a real need to develop compositions that allow the plant to use the nitrogen present in fertilizer compositions more efficiently and to control the nitrification process, in particular to increase the speed of nitrification and promote the rapid appearance of nitrates in the soil. All this with the aim of allowing better use of nitrogen by the plant, even in the limiting conditions of nitrification.

[0018] It is in this context that the applicant has highlighted, and this constitutes the basis of the present invention, that compositions comprising an extract of leaf of Cynaracan be used to stimulate the nitrification of a soil, particularly a soil with an acidic pH. These compositions allow the plant to use the nitrogen present in the soil more efficiently in order to obtain better crop productivity. Summary of the invention

[0019] Thus, the present invention, which finds application in the agro-ecological and agricultural field, aims to propose new compositions to stimulate the nitrification of a soil.

[0020] According to a first aspect, the invention relates to the use of a composition comprising an extract of leaves of Cynara to stimulate the nitrification of a soil.

[0021] According to a second aspect, the invention relates to a method for stimulating the nitrification of a soil, characterized in that it comprises the supply to said soil of an amending composition comprising an extract of leaves of Cynara. Detailed description of the invention

[0022] The term "amending composition" refers to a compound or set of compounds that can be used as a soil amendment.

[0023] A "soil amendment" or "amendment" is a method of improving the agricultural quality of a soil. Amendments are used in agriculture to improve soil productivity, particularly acidic soils.

[0024] The term "calcium basic amendment" refers to an amendment rich in calcium carbonate, for example of marine or terrestrial origin. In the context of the invention, the calcium basic amendment may be a marine limestone amendment based on debris from the shells of marine organisms, for example the amendment Calcimer ®< (Timac Agro, France).

[0025] The term "yeast extract" refers to the product resulting from the extraction of the contents of yeast cells. The extraction methods are widely described in the literature and are easy to implement by those skilled in the art. The yeast extract may be a yeast hydrolyzate. In the context of the invention, the yeast extract may be a yeast hydrolyzate of CAS reference No. 8013-01-2.

[0026] The term "hydrolyzate" refers to a product resulting from chemical decomposition by the direct or indirect action of water.

[0027] The term "legume extract" refers to the product resulting from the extraction of the contents of plant cells from the legume family. The extraction methods are widely described in the literature and are easy to implement by those skilled in the art. In the context of the invention, the legume extract from the Fabaceae family may be a soybean extract, for example a soybean permeate.

[0028] The term "permeate" refers to the liquid that has passed through the membrane of a chemical separation process (reverse osmosis, ultrafiltration). Thus, a soybean permeate refers to the liquid that has passed through the membrane of a chemical separation process from a soybean extract. The permeate can be used in liquid or solid form, for example, in powder form. A soybean permeate can be obtained by ultrafiltration of soybean wash water as described in the 2011 book Plant Science Review published by David Henning, for example, the soybean permeate marketed by Triballat Noyal (Noyal-sur-Vilaine, France).

[0029] The term "fertilizing substance(s)" or "fertilizing product(s)" means a substance, or a mixture of substances, of natural or synthetic origin, used in agriculture to promote the growth of plants by providing them with nutrients.

[0030] The term "nitrification" refers to the biological process of oxidation of ammonium (NH4 +< ) into nitrate (NO 3 -< ).

[0031] The term "stimulation of soil nitrification" or "increased soil nitrification" refers to an increase in the nitrate content in a soil.

[0032] The expression "plant" is intended to designate in this application the plant considered as a whole, including its root system, its vegetative system, the seeds, grains and fruits.

[0033] The present invention arises from the surprising advantages demonstrated by the inventors of the effect of a composition comprising an extract of leaf of Cynara on soil nitrification and crop yield.

[0034] The invention relates in fact to the use of a composition comprising an extract of leaves of Cynarato stimulate the nitrification of a soil. Said amending composition may also comprise one or more compound(s) chosen from a basic calcium amendment, a yeast extract, and a legume extract from the Fabaceae family.

[0035] The invention also relates to a method for stimulating the nitrification of a soil, characterized in that it comprises the supply to said soil of an amending composition comprising an extract of leaves of Cynara. Said amending composition may also comprise one or more compound(s) chosen from a basic calcium amendment, a yeast extract, and a legume extract from the Fabaceae family.

[0036] Cynara is a genus of perennial plants with a thistle habit in the family of Asteraceae. This genus includes several species, including: the complex Cynara cardunculus including: ∘ C. cardunculus var. scolymus (L.) Fiori, cultivated artichoke ∘ C. cardunculus var. altilisDC (= C. cardunculus subsp. cardunculus), cultivated thistle ∘ C. cardunculus var. sylvestris (Lamk.) Fiori, wild thistle Cynara syriaca Boiss. Cynara cornigera Lindely (syn. sibthornpiana Boiss. and Heldr.) Cynara algarbiensis Cosson Cynara baetica (Spreng.) Pau (syn. alba Boiss.) Cynara humilis L. Cynara cyrenaica Maire & Weiller

[0037] In a preferred embodiment of the present invention, Cynara East Cynara scolymus, more commonly known as artichoke.

[0038] To obtain an extract of leaves of Cynara, The whole plant can be used, but it is better to use the leaves. Preparing an extract of the leaves of Cynara presents no particular difficulty, many extraction methods are described in the prior art. The extraction method is not limited to a particular method, and the methods conventionally used are applicable for the preparation of an extract of leaves of Cynara,for example aqueous extraction, such as aqueous extraction obtained in Batch mode by stirring.

[0039] For example, extracts of leaf of Cynara can be obtained by a process comprising the following steps: washing, grinding, extraction (solid-liquid separation) and possibly fractionation and concentration.

[0040] In a particular embodiment, the leaf extract of Cynara is a solute of leaves of Cynara. For example, the leaf extract of Cynara can be obtained by aqueous extraction by mixing leaves of the Cynara scolymus cut and / or ground to a suitable size, possibly in powder form (e.g. 60 sieve) with water at a suitable temperature and time. An example of a preparation method is to mix a powder of leaves of Cynarawith water at 40°C for 3 hours, the mixture is then filtered to recover the liquid fraction. The liquid fraction can be used as such as an extract of leaves of Cynara or may undergo one or more subsequent treatments, for example centrifugation and / or filtration.

[0041] Leaf extract of Cynara obtained can be more or less concentrated depending on the intended use. A total dehydration of this extract allowing a presentation in water-soluble powder form can be carried out, for example, by means of a drum dryer, by atomization or by freeze-drying.

[0042] Leaf extract of Cynara used in the context of the present invention contains polyphenols derived from chlorogenic acid. Chlorogenic acid is an acid-phenol, ester of caffeic acid and (L)-quinic acid of formula:

[0043] Chlorogenic acid-derived polyphenols contained in Cynara leaf extract include cynarin, ferulylquinic acid (FAQ), p-coumarylquinic acid (PAQ), sinapylquinic acid, and dimethoxycinnamylquinic acid.

[0044] Advantageously, the extract of leaves of Cynara contains a quantity of polyphenol derived from chlorogenic acid greater than 10 mg of polyphenol derived from chlorogenic acid per 100g of dry extract, for example a quantity greater than 15 mg per 100g of dry extract, greater than 20 mg, greater than 25 mg, greater than 30 mg, greater than 35 mg, greater than 40 mg, for example between 10 mg and 100 mg or between 10 mg and 50 mg of polyphenol derived from chlorogenic acid per 100g of dry extract. The leaf extract of Cynaramay also contain a quantity of polyphenol derived from chlorogenic acid greater than 100 mg of polyphenol derived from chlorogenic acid per 100g of dry extract, for example a quantity greater than 150 mg per 100g of dry extract, greater than 250 mg, greater than 500 mg, greater than 750 mg, greater than 1000 mg, greater than 1500 mg, and even greater than 2000 mg of polyphenol derived from chlorogenic acid per 100g of dry extract.

[0045] Leaf extract of Cynara used in the context of the present invention contains cynarin. Cynarin or dicaffeylquinic acid is a biochemical compound (polyphenol) of formula:

[0046] Advantageously, the extract of leaves of Cynaracontains a quantity of cynarin greater than 2 mg per 100 g of dry extract, for example a quantity of cynarin greater than 5 mg per 100 g of dry extract, for example a quantity greater than 10 mg per 100 g of dry extract, greater than 15 mg, greater than 20 mg, greater than 25 mg, greater than 30 mg, greater than 35 mg, greater than 40 mg, for example between 2 mg and 100 mg, between 2 mg and 50 mg or between 2 mg and 6 mg of cynarin per 100 g of dry extract.

[0047] In a particular embodiment, the leaf extract of Cynara contains at least 15 mg of polyphenols derived from chlorogenic acid, including at least 3 mg of cynarin, per 100 g of dry extract. In another particular embodiment, the leaf extract of Cynara contains at least 2000 mg of polyphenols derived from chlorogenic acid, including at least 40 mg of cynarin, per 100 g of dry extract.

[0048] In a particular embodiment, the leaf extract of Cynara is an extract from Cynara scolymus here has the HPLC profile presented in Figure 1 (lower profile).

[0049] In a particular embodiment, the amending composition further comprises a yeast extract. The preparation of a yeast extract does not present any particular difficulty. Methods for preparing yeast extracts are widely described in the prior art and yeast extracts are commercially available. The extraction method is not limited to a particular method, and the methods conventionally used are applicable for the preparation of the yeast extract, for example aqueous extraction which makes it possible to obtain a yeast hydrolyzate.

[0050] Advantageously, the yeast extract is a yeast hydrolyzate. For example, a yeast hydrolyzate can be obtained by aqueous extraction by mixing yeasts with water at an appropriate temperature and duration.

[0051] In a preferred embodiment, the yeast hydrolyzate is the reference hydrolyzate CAS No. 8013-01-2. This hydrolyzate, which is sold under the trade name “Celmanax ®<”, is known for its stimulating effect on the immune system of animals. It comprises oligo-polysaccharides, including D-Galactosamine, D-Glucosamine, manno-oligosaccharides and beta-glucans.

[0052] The yeast extract obtained can be more or less concentrated depending on the intended use. Complete dehydration of this extract, allowing it to be presented in a water-soluble powder form, can be carried out, for example, using a drum dryer or by atomization.

[0053] Advantageously, the yeast extract according to the invention comprises at least 20g of manno-oligosaccharides per 100g of dry yeast extract and at least 40g of beta-glucans per 100g of dry yeast extract.

[0054] In a particular embodiment, the composition further comprises a legume extract of the Fabaceae family, preferably a soybean extract, preferably a soybean permeate. Methods for preparing legume extracts are widely described in the prior art. The extraction method is not limited to a particular method, and conventionally used methods are applicable for the preparation of the legume extract, for example aqueous extraction in a neutral or alkaline acid medium.

[0055] The legume extract obtained can be more or less concentrated depending on the intended use. Complete dehydration of this extract, allowing it to be presented in a water-soluble powder form, can be carried out, for example, using a drum dryer or by atomization.

[0056] The composition may also comprise one or more fertilizing substances conventionally used in agriculture. For example, the composition may further comprise one or more fertilizing substances selected from urea, ammonium sulfate, ammonium nitrate, phosphate, potassium chloride, ammonium sulfate, magnesium nitrate, manganese nitrate, zinc nitrate, copper nitrate, phosphoric acid, potassium nitrate and boric acid, preferably one or more fertilizing substances selected from urea, phosphate and potassium chloride.

[0057] Advantageously, the application of the amending composition to the plants will be carried out by foliar or root application. Advantageously, the amending composition is added to the soil in liquid or solid form.

[0058] In a preferred embodiment, the amending composition is provided to the soil in solid form and said composition comprises a basic calcium amendment. In this embodiment, the amending composition advantageously comprises at least 0.1% by weight of an extract of leaves of Cynara relative to the total weight of the composition, for example at least 1%, 2%, 3%, 4%, 5%, for example between 0.1% and 5% by weight of an extract of leaves of Cynara relative to the total weight of the composition. In this embodiment, the amending composition may also comprise: at least 0.1% by weight of a yeast extract relative to the total weight of the composition, for example at least 1%, 2%, 3%, 4%, 5% and 10%, preferably between 0.1% and 5% of a yeast extract relative to the total weight of the composition, and / or at least 0.1% by weight of a legume extract relative to the total weight of the composition, for example at least 1%, 2%, 3%, 4%, 5% and 10%, preferably between 0.1% and 5% by weight of a legume extract relative to the total weight of the composition.

[0059] In a particular embodiment, the amending composition used in the context of the present invention comprises: a basic calcium amendment, at least 0.1% by weight of an extract of leaves of Cynara relative to the total weight of the composition, for example at least 2%, 3%, 4%, 5% w / w, for example between 0.1% and 5% w / w of an extract of leaves of Cynararelative to the total weight of the composition, at least 0.1% by weight of a yeast extract relative to the total weight of the composition, for example at least 1%, 2%, 3%, 4%, 5% and 10%, preferably between 0.1% and 5% by weight of a yeast extract relative to the total weight of the composition, and at least 0.1% by weight of a legume extract relative to the total weight of the composition, for example at least 1%, 2%, 3%, 4%, 5% and 10%, preferably between 0.1% and 5% by weight of a legume extract relative to the total weight of the composition.

[0060] For example, the amending composition used in the context of the present invention may comprise a basic calcium amendment, 0.7% by weight of an extract of leaves of Cynara relative to the total weight of the composition, 0.2% by weight of a yeast extract relative to the total weight of the composition and 0.5% by weight of a legume extract relative to the total weight of the composition.

[0061] When the amending composition comprises a basic calcium amendment, said composition is preferably added to the soil in solid form in an amount ranging from 100 kg / ha to 2000 kg / ha (kilograms / hectare), preferably ranging from 200 kg / ha to 1200 kg / ha, preferably ranging from 400 kg / ha to 800 kg / ha, preferably about 600 kg / ha. The composition is advantageously spread homogeneously over a field or before growing plants.

[0062] In a particular embodiment, the leaf extract of Cynara is applied to the soil in an amount ranging from 1 kg / ha to 50 kg / ha (kilograms / hectare), preferably ranging from 2 kg / ha to 10 kg / ha, preferably ranging from 4 to 5 kg / ha.

[0063] In a particular embodiment, the yeast extract is added to the soil in an amount ranging from 0.5 kg / ha to 50 kg / ha (kilograms / hectare), preferably ranging from 1 kg / ha to 10 kg / ha, preferably ranging from 1 to 5 kg / ha.

[0064] In a particular embodiment, the legume extract from the Fabaceae family is added to the soil in an amount ranging from 1 kg / ha to 50 kg / ha (kilograms / hectares), preferably ranging from 2 kg / ha to 10 kg / ha, preferably ranging from 3 to 5 kg / ha.

[0065] In a particular embodiment, an extract of leaves of Cynara containing a quantity of cynarin as defined above and / or containing a quantity of polyphenols derived from chlorogenic acid as defined above is added to the soil in an amount ranging from 1 kg / ha to 50 kg / ha (kilograms / hectares), preferably ranging from 2 kg / ha to 10 kg / ha, preferably ranging from 4 to 5 kg / ha.

[0066] Although the soil treated with the amending composition may be acidic, neutral or calcareous, the treated soil is preferably acidic. When the soil is acidic, the amending composition used in the context of the present invention advantageously comprises a basic calcium amendment which makes it possible to correct the pH of the soil. It is in fact known that the assimilation of nutrients by the plant is facilitated in a soil with a neutral pH.

[0067] The applicant has in fact demonstrated that an extract of leaves of Cynara helps stimulate soil nitrification. Thus, the amending composition comprising an extract of leaves of Cynaraused in the context of the present invention makes it possible to stimulate soil nitrification. Soil nitrification makes it possible to increase the quantity of nutrients available in the soil and therefore to provide nutrients to the plant, thus meeting the growth needs of the crop which will be expressed in particular in terms of improved yield and / or the quality of the harvest.

[0068] The soil amendment composition is applied to the soil in sufficient quantity to increase soil nitrification. Soil nitrification can be measured in various ways, for example, by measuring the increase in soil nitrate content. The increase is relative to soil that has not received the composition. The nitrate content is measured using an appropriate analytical method.

[0069] Advantageously, the composition is added to the soil in a quantity sufficient to increase the nitrate content of the soil by at least 10%, at least 15%, advantageously at least 20%.

[0070] The present invention finds application in the treatment of a very wide variety of plants. Among these, we will cite in particular: large-scale crops such as cereals (wheat, corn), protein crops (peas), oilseeds (soybeans, sunflowers), prairie plants useful for animal feed, specialized crops such as market gardening (lettuce, spinach, tomatoes, melons), vines, arboriculture (pears, apples, nectarines), or horticulture (rose bushes).

[0071] The present description, not according to the invention, also describes an amending composition comprising an extract of leaves of Cynara and one or more compound(s) chosen from: a basic calcium amendment, preferably a basic calcium amendment as described above; a yeast extract, preferably a yeast extract as described above; and a legume extract from the Fabaceae family, preferably a legume extract from the Fabaceae family as described above.

[0072] Advantageously, the amending composition is in liquid form or in solid form. When the amending composition is in solid form, it preferably comprises a basic calcium amendment.

[0073] The amending composition may comprise a basic calcium amendment. Thus, the amending composition advantageously comprises at least 0.1% by weight of an extract of leaves of Cynara relative to the total weight of the composition, for example at least 1%, 2%, 3%, 4%, 5%, for example between 0.1% and 5% by weight of an extract of leaves of Cynararelative to the total weight of the composition. In this embodiment, the amending composition may also comprise: at least 0.1% by weight of a yeast extract relative to the total weight of the composition, for example at least 1%, 2%, 3%, 4%, 5% and 10%, preferably between 0.1% and 5% of a yeast extract relative to the total weight of the composition, and / or at least 0.1% by weight of a legume extract relative to the total weight of the composition, for example at least 1%, 2%, 3%, 4%, 5% and 10%, preferably between 0.1% and 5% by weight of a legume extract relative to the total weight of the composition.

[0074] In particular, the amending composition comprises: a basic calcium amendment, at least 0.1% by weight of an extract of leaves of Cynararelative to the total weight of the composition, for example at least 2%, 3%, 4%, 5% w / w, for example between 0.1% and 5% w / w of an extract of leaves of Cynara relative to the total weight of the composition, at least 0.1% by weight of a yeast extract relative to the total weight of the composition, for example at least 1%, 2%, 3%, 4%, 5% and 10%, preferably between 0.1% and 5% by weight of a yeast extract relative to the total weight of the composition, and at least 0.1% by weight of a legume extract relative to the total weight of the composition, for example at least 1%, 2%, 3%, 4%, 5% and 10%, preferably between 0.1% and 5% by weight of a legume extract relative to the total weight of the composition.

[0075] For example, the amending composition may comprise a basic calcium amendment, 0.7% by weight of an extract of leaves of Cynararelative to the total weight of the composition, 0.2% by weight of a yeast extract relative to the total weight of the composition and 0.5% by weight of a legume extract relative to the total weight of the composition.

[0076] The amending composition may further comprise one or more fertilizing substance(s) chosen from urea, ammonium sulfate, ammonium nitrate, phosphate, potassium chloride, ammonium sulfate, magnesium nitrate, manganese nitrate, zinc nitrate, copper nitrate, phosphoric acid, potassium nitrate and boric acid.

[0077] The present invention is illustrated by the following non-limiting examples. Figure legend

[0078] Figure 1 : HPLC profile showing chlorogenic acid derivatives contained in a leaf extract of Cynara scolymus(bottom profile) obtained on a reversed-phase Ib-Sil ODS column (250 mm x 4.6 mm x 5 µm) (Phenomenex USA) at room temperature (18-25 °C). Figure 2 : graph representing the amount of nitrate nitrogen in a soil, (i) treated with a composition comprising an extract of leaves of cynara scolymus (EVF), Yes “+EVF” bar and (ii) untreated, Yes “-EVF” bar. The graph shows an increase of 15% (after 2 days of incubation), 17% (after 6 days of incubation), 10% (after 15 days of incubation) and 13% (after 20 days of incubation) in the amount of nitrate in the treated soil compared to the untreated soil. Figure 3 : graph representing the number of gene copies LoveA AOB bacteria (Ammonia Oxidizing Bacteria; graph A) and AOA bacteria (Ammonia Oxidizing Archaea; graph B) in soil, (i) treated with a composition comprising an extract of leaves of cynara scolymus (EVF), Yesbar “+EVF” and (ii) unprocessed, Yes bar "-EVF". The graph shows a 144% increase (after 1 hour of incubation) in gene copy number Love AOB bacteria, and a 51% increase (after 1 hour of incubation) in gene copy number Love AOA bacteria in treated soil compared to untreated soil. Examples Example 1 : Preparation of an extract of leaves of Cvnara scolymus (artichoke) Equipment used

[0079] The following material was used: 10L KGW Jacketed Glass Reactor Lenz 400mm NS29 / 32 Glass Cooling Column Huber Unichiller 012W Circulating Chiller PTFE Stirring Paddle IKA RW20 Stirring Motor Julabo MA Büchner Immersion Thermostat Velp Scientifica JPV Recirculating Water Vacuum Pump Fischer 200 µm Nylon Filter Cloth Beckman Coulter Avanti J-26 XP Centrifuge Beckman Coulter J-Lite PP-1000 Buckets For extraction

[0080] The 10L jacketed glass reactor (KGW) was equipped with an immersion thermostat (Julabo MA) to adjust the temperature of the extraction medium. The reactor was topped with a glass column (Lenz 400mm NS29 / 32) connected to a recirculating chiller (Huber Unichiller 012W). The extraction medium was stirred by a PTFE paddle powered by a stirring motor (IKA RW20). For filtration

[0081] Filtration of the extract was carried out on a Bücher funnel using a water recirculation vacuum pump (Velp Scientifica JPV). The filter used was cut to the dimensions of the Büchner funnel from a 200 µm nylon filter cloth (Fischer). For centrifugation

[0082] An Avanti J-26 XP centrifuge and J-Lite PP-1000 buckets (Beckman Coulter) were used. Protocols Preparation of an extract of Cynara scolymus (Extract A)

[0083] 4000 g of water were introduced into a 10L glass beaker. The water was heated to 40°C with gentle stirring. 1000 g of artichoke leaf powder titrated in cynarin (Tortay langeais 37130 - France) was added to the water with stirring. When the artichoke leaf powder was dispersed in water, the pH was in the order of 5-6. The pH was adjusted to 7 with a 30% w / w sodium hydroxide solution (Quaron). The resulting mixture was kept stirring for 3 hours at 40°C on a VWR VMS-A IP21 magnetic stirrer hotplate.

[0084] The mixture was filtered through a Büchner funnel on a 200 µm nylon mesh by applying a partial vacuum with a Waston Marlow pump. The liquid fraction was collected (filtrate) and centrifuged at 7000 rpm, at 15 °C for 20 min in a Bechman Coulter centrifuge. The extract obtained (Extract A) after filtration was stored at -80 °C in a Liebherr Scientific ultra-low temperature vertical laboratory freezer until use. Measurement of the amount of cynarin in a Cynara extract (cynarin titration) by HPLC-UV: example of extract A

[0085] Extract A (70 µl) was mixed with 30 µl of Tris / HCl (pH 8.75; 2M) and 20 mg of alumina, stirred for 5 min with a magnetic stir bar and centrifuged (10000 g, 5 min) in a Beckman Coulter centrifuge. The precipitate containing insoluble cynarin was washed once with Milliq ultrapure water (1 ml).

[0086] Cynarin, soluble in acid medium, was resolubilized with 70 µl phosphoric acid (0.4 M) and then the mixture was centrifuged (10000 g, 5 min) with a Beckman Coulter centrifuge. The cynarin remained in the supernatant.

[0087] Aliquots of 20 µl of the supernatant were injected into a Varian 9012 chromatographic apparatus including a 20 µl injection valve (Rheodyne USA) and a Varian 9050 ultraviolet detector and set at 316 nm. A reverse-phase Ib-Sil ODS column (250 mm x 4.6 mm x 5 µm) (Phenomenex USA) was used. The chromatographic protocol was carried out at room temperature (18-25 °C).

[0088] The column was eluted with a water / methanol / acetic acid mixture (78.5:20:2.5, v / v / v). The mobile phase was injected at a flow rate of 1.3 ml / min. The results obtained were compared to a calibration line obtained with standard cynarin solutions. The standard cynarin solutions were obtained from a stock solution of 0.1 mg / ml of cynarin prepared in a methanol:water mixture (1:1, v / v). The standard cynarin solutions that allowed the calibration line to be obtained were obtained by diluting the stock solution in the same methanol:water mixture (1:1, v / v). Characterization of extract A by HPLC-UV

[0089] Extract A consisted mainly of cynarin and other polyphenols derived from chlorogenic acid in the following proportions: Cynarin: 41.7 mg / 100g dry extract Other polyphenols derived from chlorogenic acid: 2291.3 mg / 100g dry extract Total polyphenols derived from chlorogenic acid: 2333.0 mg / 100g dry extract Example 2 : Measurement of the stimulation of nitrification of a soil by measuring the increase in the nitrate content of the soil Soil preparation

[0090] 10 g of dry soil (Table 1) sieved through a 2 mm mesh sieve were placed in 60 ml glass bottles to which 1 ml of water was added, this volume reaching 70% of the field capacity of the soil studied. After 1 h of incubation, the treatments were applied. Table 1: Main soil characteristics Texture Silty clay pH 8,2 Organic matter (% by mass) 5 Cation exchange capacity (meq / 100g) 19,2 Soil treated with leaf extract Cynara scolymus (+EVF)

[0091] 10 g of dry soil sieved through a 2 mm mesh sieve were placed in 60 ml glass bottles to which 1 ml of water was added, this volume allowing to reach 70% of the field capacity of the soil studied. After 1 hour of incubation, 30 kg / ha of nitrogen in the form of ammonium sulfate was added. The leaf extract Cynara scolymus (EVF) was applied at a dose corresponding to a treatment of 1 kg / ha. The bottles were then tightly sealed and incubated at 10°C for up to 20 days. During this period, the nitrification kinetics associated with the appearance of nitrate in the soil were established by carrying out nitrate measurements at 2, 6, 15 and 20 days. Untreated soil (-EVF)

[0092] 10 g of dry soil sieved through a 2 mm mesh sieve were placed in 60 ml glass flasks to which 1 ml of water was added, this volume reaching 70% of the field capacity of the soil studied. After 1 hour of incubation, 30 kg / ha of nitrogen in the form of ammonium sulfate was added. The flasks were then hermetically sealed and incubated at 10°C for up to 20 days. During this period, the nitrification kinetics associated with the appearance of nitrate in the soil were established by performing nitrate measurements at 2, 6, 15 and 20 days. Extraction of nitrates from soil

[0093] Extraction was performed by adding 30 mL of pure water to the flask containing the 10 g of soil and then stirring using a rotary shaker for one hour. The flasks were allowed to settle for 10 min. The supernatant was collected and centrifuged at 11,000 rpm (rotations per minute) for 5 min at 4°C and then filtered through a 0.25 µm filter to remove any particles. Soil nitrate determination

[0094] Nitrate content was determined by high-performance ion chromatography (HPIC, ICS 5000+). 25 µl of filtered extract was injected using an autosampler. Samples were eluted using a solution composed of methanesulfonic acid (MSA; 20 mM) delivered by an isocratic pump system. Sample cations were detected, after separation, using a conductometric detector. Nitrate was quantified by calibrating the system with standard solutions.

[0095] For each of the incubation conditions (+EVF and -EVF), four batches of soil were created (1 batch = 1 biological repetition).

[0096] All treatments were carried out systematically for each of the biological replicates, i.e. in quadruplicate. The data obtained were presented as the mean and the variability of the results was given as the standard error of the mean for n=4. A statistical analysis of the results was carried out using the Student t test.

[0097] The dosage of nitrate content is presented in the Figure 2 .

[0098] Conclusion: Soils treated with leaf extract of Cynara scolymus (+EVF) showed a significant increase in soil nitrate content: +15% (after 2 days of incubation), +17% (after 6 days of incubation), +10% (after 15 days of incubation) and +13% (after 20 days of incubation). Example 3 : Measurement of the stimulation of nitrification of a soil by measuring the decrease in soil pH Soil preparation

[0099] 80 g of dry soil (Table 1) sieved with a sieve with a mesh diameter of 2 mm, were placed in 90 cm 3< (5.4 * 4 * 4.2 cm) plexiglass tanks, an optode was glued on one of the transparent faces of the plexiglass tanks to which 15 ml of water were added, this volume allowing to reach 70% of the field capacity of the soil studied. After 24 h of incubation, the treatments were applied. Soil treated with leaf extract Cynara scolymus (+EVF)

[0100] 80 g of dry soil (Table 1) sieved with a sieve with a mesh diameter of 2 mm, were placed in 90 cm 3< (5.4 * 4 * 4.2 cm) plexiglass tanks, an optode was glued on one of the transparent faces of the plexiglass tanks to which 15 ml of water were added, this volume allowing to reach 70% of the field capacity of the soil studied. After 24 h of incubation, the treatments were applied.

[0101] 80 kg / ha of nitrogen in the form of ammonium sulfate was then added. The leaf extract of Cynara scolymus (+EVF) was applied at a dose corresponding to a treatment of 1 kg / ha. The tanks were then placed in the dark for 13 days. Photographs of the optode were taken after 4, 5, 6, 7, 8, 9, 10, 11, 12 and 13 days using a camera connected to a computer. Each photo was then analyzed by the imaging software (VisiSens) to determine the change in pH (by measuring the change in fluorescence) during this period. Untreated soil with leaf extract Cynara scolymus (+EVF)

[0102] 80 g of dry soil (Table 1) sieved with a sieve with a mesh diameter of 2 mm, were placed in 90 cm 3< (5.4 * 4 * 4.2 cm) plexiglass tanks, an optode was glued on one of the transparent faces of the plexiglass tanks to which 15 ml of water were added, this volume allowing to reach 70% of the field capacity of the soil studied. After 24 h of incubation, the treatments were applied.

[0103] 80 kg / ha of nitrogen in the form of ammonium sulfate was then added. The tanks were then placed in the dark for 13 days. Photographs of the optode were taken after 4, 5, 6, 7, 8, 9, 10, 11, 12 and 13 days using a camera connected to a computer. Each photo was then analyzed by imaging software (VisiSens) to determine the change in fluorescence over this period.

[0104] The evolution of soil pH was visualized by VisiSens software (photographic data not shown).

[0105] Conclusion: Soils treated with leaf extract of Cynara scolymus (+EVF) showed a decrease in soil pH between 4 and 13 days of incubation, indicating soil acidification related to the stimulation of soil nitrification. Example 3 : Measurement of the stimulation of nitrification of a soil by measuring the increase in the number of copies of the gene in the soil AmoA (gene involved in the synthesis of the enzyme ammonia monooxygenase responsible for the transformation of ammonium into nitrate) Soil preparation

[0106] 10 g of dry soil (Table 2) sieved through a 2 mm mesh sieve were placed in 60 ml glass bottles to which 1 ml of water was added, this volume reaching 70% of the field capacity of the soil studied. After 1 hour of incubation, the treatments were applied. Table 2: Main soil characteristics Texture Silty pH 6,2 Organic matter (%) 3,6 Cation exchange capacity (meq / 100g) 8,2 Soil treated with an extract of leaves of Cynara scolymus (+EVF)

[0107] 10 g of dry soil (Table 2) sieved through a 2 mm mesh sieve were placed in 60 ml glass bottles to which 1 ml of water was added, this volume reaching 70% of the field capacity of the soil studied. After 1 hour of incubation, the leaf extract of Cynara scolymus (+EVF) was applied at a dose of 1 kg / ha. The flasks were then tightly sealed and incubated at room temperature for a period of one hour. After this period, the gene copy number AmoA was measured by quantitative PCR. Untreated soil with leaf extract Cynara scolymus (-EVF)

[0108] 10 g of dry soil (Table 2) sieved through a 2 mm mesh sieve were placed in 60 ml glass vials to which 1 ml of water was added, this volume reaching 70% of the field capacity of the soil studied. After 1 hour of incubation, the vials were then tightly closed and incubated at room temperature for a period of one hour. After this period, the gene copy number AmoA was measured by quantitative PCR. Extraction of DNA from soil samples

[0109] DNA was extracted from soil samples using the Nucleospin Soil Extraction Kit (Macherey Nagel) and following the manufacturer's instructions. For all samples, DNA was eluted in 50 µl of elution buffer. DNA quality analysis

[0110] After DNA extraction and elution, DNA quality and concentration were analyzed using the Agilent Technologies automated 4200 TapeStation System and genomic DNA screentapes software. Gene copy number analysis AmoA by qPCR

[0111] The number of copies of the gene AmoA was measured by qPCR using primers specific for this gene. For AOA-amoA F (SAATGGTCTGGCTTAGACG), AOA-amoA R (GCG-GCCATCCATCTGTATGT) and for AOB-amoA F (GGGGTTTCTACTGGTGGT), AOB-amoA R (CCCCTTCGGGAAAGCCTTCTTC). Standard DNAs were created by PCR amplification of soil DNA extracts. The resulting amplicons were purified before quantification in the “TapeStation” system. The copy number of the target genes was calculated by the following formula:

[0112] Standard curves for the gene AmoAAOB and AOA bacteria were performed using a DNA dilution series ranging from 101 to 106 copies of the target gene. The standard, DNA samples, and control were amplified in three replicates with the respective primer pairs. All reactions were performed using the Biorad CFX384 Real-Time PCR System, with an initial denaturation at 98°C for 3 min, followed by 40 cycles of 98°C for 15s, 65°C for 30s, and 72°C for 50s, and a final extension at 72°C for 5 min. Each 10 µl reaction contained 1 µl of DNA and a 300 nM concentration of each primer. Samples were quantified against the corresponding standard curve using CFX Manager software version 3.1 (BIORAD). The final calculation of gene copy number was calculated and reported per gram of soil.

[0113] For each of the incubation conditions (+EVF and -EVF), four batches of soil were created (1 batch = 1 biological repetition).

[0114] All treatments were carried out systematically for each of the biological replicates, i.e. in quadruplicate. The data obtained were presented as the mean and the variability of the results was given as the standard error of the mean for n=4. A statistical analysis of the results was carried out using the Student t test.

[0115] The gene copy number AmoA AOB and AOA bacteria is presented in the Figure 3 .

[0116] Conclusion: Soils treated with leaf extract of Cynara scolymus (+EVF) show a significant increase in gene copy number I love you AOB bacteria (+144%) and AOA bacteria (+51%) after 1 hour of incubation.

Claims

1. Use of an amendment composition comprising an extract of Cynara leaves for stimulating the nitrification of a soil.

2. The use as claimed in claim 1, wherein the composition further comprises one or more compound(s) selected from: - a basic calcium amendment, - a yeast extract, - a legume extract from the family Fabaceae, and - eventually one or more fertilizer substance(s) selected from urea, ammonium sulfate, ammonium nitrate, phosphate, potassium chloride, ammonium sulfate, magnesium nitrate, manganese nitrate, zinc nitrate, copper nitrate, phosphoric acid, potassium nitrate and boric acid.

3. The use as claimed in any one of claims 1 to 2, wherein Cynara is Cynara scolymus.

4. The use as claimed in any one of claims 2 to 3, wherein the yeast extract is a yeast hydrolysate, preferably a yeast hydrolysate with CAS No. 8013-01-2.

5. The use as claimed in any one of claims 2 to 4, wherein the extract of a legume of the family Fabaceae is a soybean extract, preferably a soybean permeate.

6. The use as claimed in any one of claims 1 to 5, wherein the soil is acidic soil.

7. The use as claimed in any one of claims 1 to 6, wherein the extract of Cynara leaves is applied to the soil in an amount ranging from 1 kg / ha to 50 kg / ha (kilograms / hectare), preferably from 2 kg / ha to 10 kg / ha, preferably from 4 to 5 kg / ha.

8. A process for stimulating the nitrification of a soil, characterized in that it comprises supplying to said soil an amendment composition comprising an extract of Cynara leaves.

9. The process as claimed in claim 8, wherein the composition further comprises one or more compound(s) selected from: - a basic calcium amendment, - a yeast extract, - a legume extract from the family Fabaceae, and - eventually one or more fertilizer substance(s) selected from urea, ammonium sulfate, ammonium nitrate, phosphate, potassium chloride, ammonium sulfate, magnesium nitrate, manganese nitrate, zinc nitrate, copper nitrate, phosphoric acid, potassium nitrate and boric acid.

10. The process as claimed in any one of claims 8 to 9, wherein Cynara is Cynara scolymus.

11. The process as claimed in any one of claims 9 to 10, wherein the yeast extract is a yeast hydrolysate, preferably with CAS No. 8013-01-2.

12. The process as claimed in any one of claims 9 to 11, wherein the extract of a legume of the family Fabaceae is a soybean extract, preferably a soybean permeate.

13. The process as claimed in any one of claims 8 to 12, wherein the soil is an acidic soil.

14. The process as claimed in any one of claims 8 to 13, wherein the extract of Cynara leaves is applied to the soil in an amount ranging from 1 kg / ha to 50 kg / ha (kilograms / hectare), preferably from 2 kg / ha to 10 kg / ha, preferably from 4 to 5 kg / ha.