Fertilizing composition promoting the development of mycorrhizae

Abstract

The present invention relates to a fertilizing composition promoting the development of mycorrhizae comprising struvite and a mycorrhizal fungus.

Description

Description Title of the invention: Fertilizing composition promoting the development of mycorrhizae

[0001] TECHNICAL FIELD

[0002] The present invention relates to a fertilizing composition promoting the development of mycorrhizae.

[0003] STATE OF THE ART

[0004] Mycorrhizae are a plant symbiosis that involves "the association of a photosynthetic organism, i.e., a green plant, and a filamentous fungus." This phenomenon affects the vast majority of green plants. In the case of mycorrhizae, the plant produces carbon compounds through photosynthesis, and in exchange, the fungus provides the plant with mineral elements from the growing soil. In order to establish mycorrhizae, the fungus colonizes the plant's root system with its mycelium, made up of hyphae (filamentous vegetative elements). The hyphal network extends much further than the plant's roots and can therefore seek out more of the low-mobility phosphorus available in the soil. In addition to the nutrient advantage, mycorrhizae offer other benefits: better resistance to pathogens, insects, drought, stress, and a positive impact on soil aggregation.Consequently, in order to promote sustainable agriculture consuming less mineral fertilizers in view of current climate challenges, promoting the development of mycorrhizae is of capital importance.

[0005] However, mycorrhizae are virtually never taken into account by agriculture. We have currently lost 90% of these mycorrhizae in cultivated soils worldwide and it has recently been determined that one of the main contributors to the disappearance of these mycorrhizae is the use of conventional phosphate fertilizers such as DAP. When these fertilizers hydrolyze, the raw phosphoric acid attacks the hyphae, resulting in their destruction. In addition, the addition of inorganic phosphate greatly reduces the plant's interest in feeding mycorrhizal fungi since it can access this resource itself.

[0006] Phosphate is used extensively in the form of chemical fertilizers in our agriculture. Each year, more than 45 million tons of phosphate fertilizers are consumed worldwide to meet global food demand. However, the phosphorus used for fertilizer production comes from non-renewable resources. In addition to their negative impact on mycorrhizae, the depletion of phosphorus resources poses a major risk to food security. With this in mind, it is also imperative to find solutions to limit the use of non-renewable phosphate fertilizers.

[0007] In view of the above, there is therefore a need for a fertilizing composition based on renewable phosphate fertilizers promoting the development of mycorrhizae.

[0008] DESCRIPTION OF THE INVENTION

[0009] The inventors surprisingly determined that the use of struvite in combination with at least one mycorrhizal fungus made it possible to ensure and improve plant nutrition by increasing the phosphorus content in the plants while promoting the development of mycorrhizae, unlike the use of conventional phosphate fertilizers such as DAP (see example 1).

[0010] According to one aspect of the present invention, there is provided a fertilizer composition promoting the development of mycorrhizae comprising struvite and at least one mycorrhizal fungus.

[0011] According to one embodiment, the fertilizing composition according to the invention comprises between 5% and 99.9%, between 25% and 98%, between 50% and 97%, between 75% and 96% or between 85 and 95% by weight of struvite, preferably between 88% and 92% by weight of struvite and between 0.1% and 15%, preferably between 0.3% and 10%, even more preferably between 0.4% and 5% by weight of at least one mycorrhizal fungus.

[0012] Struvite is a mineral of the hydrated phosphate family, a double ammonium and magnesium phosphate hexahydrate with the formula chemical NH4MgPO4. It is a mineral naturally present in manure and guano, as well as in pathologies of the urine and renal tract.

[0013] Struvite contains approximately per kilogram of crystalline struvite 126.2 g of phosphorus or 387.0 g of phosphate 57.1 g of nitrogen or 73.5 g of ammoniacal nitrogen and 99.0 g of magnesium.

[0014] Struvite is a problem in wastewater treatment plants due to the accumulation of its crystals in pipes and a reduction in water flow. Currently, many methods exist to control struvite nucleation in wastewater treatment plants and reduce the amount of phosphate entering water bodies.

[0015] There is considerable interest in recycling phosphorus (P) in the form of struvite for environmental, economic, and commercial reasons. Rather than generating a waste product for disposal, recovered struvite phosphate can be advantageously used as a fertilizer and also deserves the designation "renewable fertilizer" due to its source.

[0016] An additional advantage of struvite is its limited solubility. The fertilizer dissolves over time to provide nutrients at a rate that plants can utilize. Highly soluble fertilizers tend to release nutrients at a faster rate than plant absorption, resulting in fertilizer waste and negative environmental impacts.

[0017] According to one embodiment, the fertilizer composition comprises less than 99.9%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25% or 20% by weight of struvite and / or comprises more than 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80% or 85% by weight of struvite.

[0018] Mycorrhizal fungi are fungi that have the particularity of entering into symbiosis with plant roots (common agreement between the two organisms). A mycorrhizal fungus is further characterized by the fact that it is a benign soil fungus that is beneficial to plants. The mycorrhizal fungus cannot extract from the soil the carbon compounds necessary for its growth and development. The mycorrhizal fungus therefore uses the carbon compounds resulting from the symbiosis with the plant, which produces these compounds through photosynthesis. The mycorrhizal fungus can, among other things, absorb nutrients that are difficult for plants to assimilate. These include phosphate compounds, nitrogen compounds, and metal ions, including potassium, calcium, and magnesium, as well as trace elements that are fixed in poorly soluble complexes. The plant benefits from this symbiosis because it can more easily access these nutrients via the mycorrhizal fungus. This mutualistic cooperation results in a self-sustaining system, but also leads to a synergistic effect. In fact, the mycorrhizal fungus is able to absorb more nutrients, and the plant experiences improved growth and development, so that more mycorrhizal fungi can live with the plant.Cooperation is therefore long-term and possible without intensive external management.

[0019] In a preferred embodiment, the mycorrhizal fungus is selected from the group consisting of an arbuscular mycorrhizal fungus, an ecto-mycorrhizal fungus, an ectendo-mycorrhizal fungus and an ericoid mycorrhizal fungus or a combination thereof.

[0020] Arbuscular mycorrhizal fungi are characterized by exhibiting intracellular growth within plant cells where they form arbuscules and vesicles. Arbuscules are highly branched, tree-like structures that contribute to the exchange of carbon and nutrients, such as nitrogen and phosphate. Vesicles are bladder-like structures, which are attributed with the function of nutrient storage. Arbuscular mycorrhizal fungi form underground fruiting bodies. Preferred embodiments include, but are not limited to, Glomus mosseae and Glomus intraradices.

[0021] Ecto-mycorrhizal fungi do not form arbuscules and vesicles. Instead, ecto-mycorrhizal fungi grow around and inside the roots, where they form a specific structure called a "salt net." The fungal threads that form the Hartig net grow intercellularly. By growing around the roots, ecto- Mycorrhizae form a layer around the root. The color and shape of the layer can vary depending on the species of ecto-mycorrhizal fungi. In the Hartig network, there is an exchange of nutrients, particularly nitrogen and phosphate, and carbon. Ecto-mycorrhizal fungi form aerial fruiting bodies. Preferred embodiments include, but are not limited to, Laccaria laccata, Boletus edulis, Cantharellus cibarius, and Paxillus involutus.

[0022] Ecto-mycorrhizal fungi are characterized in that they do not form arbuscules and vesicles and grow intracellularly in the root cells. Ecto-mycorrhizal fungi also form a so-called "salted net", but this is significantly finer than with ecto-mycorrhizal fungi. Ecto-mycorrhizal fungi can form an aerial fruiting body. Preferred embodiments relate to, but are not limited to, Tuber, Tricharlna and Wilcoxina species.

[0023] Ericoid mycorrhizal fungi are characterized by intracellular growth in root cells. Ericoid mycorrhizal fungi do not form a layer, a so-called "Hartig" filament, arbuscules, or vesicles. Ericoid mycorrhizal fungi form characteristic curved structures. Preferred embodiments include, but are not limited to, Hymenoscyphus ericae, Rhizoscyphus spp., and Oidiodendron spp.

[0024] Said mycorrhizal fungi, in particular a combination of different mycorrhizal fungi or different types of mycorrhizal fungi, are suitable according to the invention. These combinations have an advantageous effect in particular due to the compatibility that occurs between the different species. The overlap of non-corresponding properties such as cold tolerance, adaptation to soil conditions, tolerance to drought or waterlogging or cooperation with the plant species of choice leads to an advantage when using different species or different types of mycorrhizal fungi.

[0025] The inventors surprisingly determined that using struvite in combination with at least one mycorrhizal fungus allowed to ensure and improve plant nutrition while promoting the development of mycorrhizae, unlike the use of classic phosphate fertilizers such as DAP (see example 1).

[0026] According to one embodiment, the fertilizing composition further comprises at least two trace elements, at least one secondary element, and at least one clay.

[0027] According to one embodiment, the fertilizing composition according to the invention further comprises - between 0.005% and 10%, between 0.01% and 5%, between 0.025% and 2.5%, or between 0.05% and 1%, preferably between 0.1% and 0.55% by weight of a first trace element; - between 0.005% and 10%, between 0.01% and 5%, between 0.05% and 4%, or between 0.1% and 3%, preferably between 0.5% and 2.8% by weight of a second trace element; - between 0.25% and 10%, between 0.5% and 5%, or between 0.75% and 4.5%, preferably between 1% and 4% by weight of a secondary element; and - between 0.1% and 10%, between 0.25% and 5%, or between 0.5% and 3%, preferably between 0.6% and 2.6% by weight of at least one clay.

[0028] The at least first and second trace elements may be selected from the group consisting of Manganese, Manganese Sulfate, Iron, Zinc, Zinc Oxide, Zinc Sulfate, Copper, Molybdenum, Cobalt, Sodium Chloride, Potassium Chloride, Ferric Sulfate, Copper Sulfate, Cobalt Chloride, Chlorine, Boron, Nickel, Vanadium, Silicon, Iron Chelate, Copper Chelate, Zinc Chelate, Manganese Chelate, Boron Chelate, Molybdenum Chelate, Selenium, Sodium Selenite, preferably molybdenum, nickel, copper, zinc, zinc oxide, manganese, boron, iron, selenium, sodium selenite and chlorine, more preferably zinc oxide and selenium or sodium selenite, even more preferably the first trace element is selenium and the second trace element is zinc oxide.

[0029] The at least one secondary element may be selected from the group consisting of urea, magnesium, magnesium carbonate, magnesium oxide, magnesium chloride, ammonium chloride, ammonium molybdate, ammonium nitrosulfate, potassium nitrate, ammonium sulfate, ammonium nitrate, calcium nitrate, calcium sulfate potassium, Monoammonium Phosphate, Potassium Chloride, Calcium Chloride, Calcium Sulfate, Magnesium Sulfate, Magnesium Chloride, Sodium Chloride, Diammonium Phosphate, Ammonium Chloride, Monocalcium Phosphate, Dicalcium Phosphate, Tricalcium Phosphate, Simple Superphosphate, Triple Superphosphate, Zinc Sulfate, Iron Sulfate, Calcium Phosphate, Monopotassium Phosphate, Sodium Nitrate, Magnesium Nitrate, Potassium Phosphate, Potassium Bicarbonate, Potassium Sulfite, Calcium Sulfate, Potassium Oxide, Ammonium Phosphate, Magnesium Oxide, Polyphosphate, Ammonium Sulfamate, Ammonium Carbonate, Sulfur, Potassium Carbonate, Potassium Hydrogen Phosphate, preferably sulfate ammonium.

[0030] The at least one clay may be selected from the group consisting of sepiolite, bentonite, kaolinite, illite, montmorillonite, vermiculite, halloysite, attapulgite, saponite, chlorite, mica, illite-montmorillonite, smectite, heulandite and mixtures thereof, preferably sepiolite.

[0031] According to a preferred embodiment of the invention, the fertilizing composition according to the invention further comprises between 0.005% and 10%, between 0.01% and 5%, between 0.025% and 2.5%, or between 0.05% and 1%, preferably between 0.1% and 0.55% by weight of selenium; between 0.005% and 10%, between 0.01% and 5%, between 0.05% and 4%, or between 0.1% and 3%, preferably between 0.5% and 2.8% by weight of zinc oxide; between 0.25% and 10%, between 0.5% and 5%, or between 0.75% and 4.5%, preferably between 1% and 4% by weight of ammonium sulfate; and between 0.1% and 10%, between 0.25% and 5%, or between 0.5% and 3%, preferably between 0.6% and 2.6% by weight of sepiolite.

[0032] According to one embodiment, the fertilizing composition according to the invention is in the form of a powder, an emulsion in water, or in granulated form, preferably in granulated form.

[0033] Preferably, the fertilizer composition is applied at a rate of 2.5 to 500 kg / ha, 5 to 200 kg / ha, 10 to 100 kg / ha, preferably 15 to 50 kg / ha.

[0034] According to one embodiment, the fertilizing composition according to the invention is included in or consists of the core of a granular fertilizer.

[0035] According to one embodiment, the final product intended to be applied in the soil is the combination by mixing (blend) or by granulation of the composition according to the invention with additional raw materials.

[0036] The fertilizing composition according to the invention may further comprise or be combined with other components chosen for example from binders, additives, fillers, fillers and minerals.

[0037] The fertilizer composition may include or be combined with, but is not limited to: ammonium sulfate, ammonium nitrate, ammonium sulfate nitrate, ammonium chloride, ammonium bisulfate, ammonium polysulfide, ammonium thiosulfate, aqueous ammonia, anhydrous ammonia, ammonium polyphosphate, aluminum sulfate, calcium nitrate, calcium ammonium nitrate, sulfate, calcined magnesite, calcitic limestone, calcium oxide, calcium nitrate, dolomitic limestone, hydrated lime, calcium carbonate, diammonium phosphate, monoammonium phosphate, magnesium nitrate, magnesium sulfate, potassium nitrate, potassium chloride, potassium carbonate, potassium magnesium sulfate, potassium sulfate, sodium nitrates, magnesium limestone, magnesia, urea, urea-formaldehydes, urea ammonium nitrate, urea coated with sulfur, polymer-coated urea, isobutylidene diurea, K2SO4-2MgSO4, kainite, sylvinite,kieserite, Epsom salts, elemental sulfur, marl, crushed oyster shells, fish meal, fish cakes, fish manure, blood meal, phosphate rock, super phosphates, slag, bone meal, fish wood, manure, bat guano, peat moss, compost, green sand, cottonseed meal, feather meal, crab meal, fish emulsion, amino acid hydrolysates, sugars, organic acids, diamines and polyamines, humic extracts, organic amendments, biostimulants, seaweed extracts, plant extracts, live microorganisms, microorganism extracts or a combination thereof., Preferably between 0% and 80%, more preferably between 0% and 70%, more preferably between 0% and 50% by weight of the above compounds is present in the fertilizing composition according to the invention.

[0038] According to another aspect of the invention, the fertilizing composition according to the invention is combined with at least one other complementary fertilizer chosen from nitrogen fertilizers, potassium fertilizers, phosphate fertilizers, binary (NP,PK) and ternary (NPK) fertilizers as well as their combinations, and alternatively in association with calcium amendments, trace elements, boric acid, leonardite, organic amendments and feldspar, one or more biostimulants chosen from the group consisting of amino acid hydrolysates, humic extracts, algae extracts, plant extracts, living microorganisms, microorganism extracts and their combinations.

[0039] Said combination of the fertilizing composition according to the invention with at least one other complementary fertilizer can be used in granular, emulsion or powder form, preferably in that it is applied at a rate of 2.5 to 500 kg / ha, 5 to 200 kg / ha, 10 to 100 kg / ha, preferably 15 to 50 kg / ha.

[0040] According to one embodiment, the sugars of said at least one complementary fertilizer are chosen from mono- and di-saccharides, preferably sucrose, fructose, trehalose, glucose, arabinose, maltose, as well as mixtures thereof.

[0041] According to one embodiment, the amino acids of said at least one complementary fertilizer are chosen from threonine, lysine, phenylalanine, glutamic acid, methionine, GABA, ornithine, glycine, glutamine, aspartic acid, serine, asparagine, tyrosine, tryptophan, valine, leucine, isoleucine, proline, 4-hydroxyproline, arginine, histidine, alanine, cysteine ​​and mixtures thereof.

[0042] According to one embodiment, the organic acids of said at least one complementary fertilizer are chosen from lactic acid, succinic acid, oxalic acid, gluconic acid, threonic acid, fumaric acid, syringic acid and mixtures thereof.

[0043] According to one embodiment, the diamines and polyamines of said at least one complementary fertilizer are chosen from cadaverine, putrescine, spermidine, spermine and mixtures thereof.

[0044] According to one embodiment of said combination of the fertilizing composition according to the invention with at least one other complementary fertilizer, the fertilizing composition according to the invention is present in an amount of 10 to 60% by weight.

[0045] According to one embodiment of said combination of the fertilizing composition according to the invention with at least one other complementary fertilizer, the complementary nitrogen fertilizer is present at a rate of 5 to 90% by weight and is chosen from urea, ammonium nitrosulfate, potassium nitrate, ammonium sulfate, ammonium nitrate, calcium nitrate.

[0046] According to one embodiment of said combination of the fertilizing composition according to the invention with at least one other complementary fertilizer, the additional potassium fertilizer is present at a rate of 5 to 90% by weight and is chosen from potassium chloride, potassium sulfate and potassium hydroxide.

[0047] According to one embodiment of said combination of the fertilizing composition according to the invention with at least one other complementary fertilizer, the additional calcium fertilizer is present at a rate of 5 to 90% by weight and is chosen from calcium chloride, calcium cyanamide, calcium sulfate, dolomite, limestone, calcium oxide, calcium hydroxide.

[0048] According to one embodiment of said combination of the fertilizing composition according to the invention with at least one other complementary fertilizer, the complementary trace element fertilizer is present in an amount of 1 to 30% by weight and is chosen from ferric sulfate, zinc sulfate, manganese sulfate, copper sulfate, ammonium molybdate, cobalt chloride, iron, zinc, manganese and / or copper micronutrients associated with the complexing agents humate, citrate, gluconate, heptagluconate and amino acids or with the chelating agents ethylenediaminetetraacetic acid, ethylenediamine-di(o-hydroxyphenyl-acetic acid, diethylenetriaminepentaacetic acid.

[0049] According to one embodiment of said combination of the fertilizing composition according to the invention with at least one other complementary fertilizer, the complementary organic amendment is present at a rate of 5 to 90% by weight and is chosen from bovine, ovine, porcine, mink, rabbit and hen droppings.

[0050] According to one embodiment of said combination of the fertilizing composition according to the invention with at least one other complementary fertilizer, the biostimulants are present at a rate of 5 to 90% by weight.

[0051] According to one embodiment, the live microorganisms or microorganism extracts are chosen from the family Thiorhodaceae, Athiorhodaceae, Chlorobacteriaceae, Nitrobacter, preferably of the genus Nitrosomonas or Nitrobacter, Thiobacteriaceae preferably of the genus Thiobacillus, Methanomonadaceae preferably of the genus Hydrogenomonas, Carboxydomonas or Methanomonas, Caulobacteriaceae, Siderocapsaceae, Pseudomonaceae preferably of the genus Pseudomonas, Xanthomonas, Acetobacter or Azotomonas, Spiri llaceae preferably of the genus Vibrio, Cellvibrio, Cellfalcicula, Desulfovibrio or Spirillum, Azotobacter, preferably of the genus Azotobacter, Beijerinckia or Derxia, Rhizobacter, preferably of the genus Rhizobium, Chromobacterium or Agrobacterium, Achrobacteriums, preferably of the genus Achromobacter or Flavobacterium, Enterobacteriaceae, preferably of the genus Escherichia, Proteus, Aerobacter or Serratia, Micrococcaceae, preferably of the genus Micrococcus or Sarcina, Brevibacteraceae preferably of the genus Brevibacterium, Lactobacillaceae preferably of the genus Streptococcus, Leuconostoc or Lactobacillus, Corynebacteraceae preferably of the genus Corynebacterium, Cellulomonas or Arthrobacter, Bacillaceae preferably of the genus Bacillus or Clostridium, and mixtures thereof. Preferably, the live microorganisms or extracts of microorganisms are chosen from the species Pichia guilliermondii, Azotobacterchroococcum, Azotobacter vinelandii, Azospirillum lipoferum, Bacillus megaterium, Bacillus aryabhattai, Bacillus amiloliquefaciens, Bacillus licheniformis and Oceanobacillus picturae, and mixtures thereof.

[0052] According to another aspect of the invention, the invention relates to a method for stimulating the roots of plants and / or for stimulating the development of mycorrhizae comprising the application of the fertilizing composition according to the invention on or in said soil, preferably in that said composition according to the invention is applied at a rate of 2.5 to 500 kg / ha, 5 to 200 kg / ha, 10 to 100 kg / ha, preferably 15 to 50 kg / ha.

[0053] According to another aspect of the invention, the invention relates to the use of struvite in combination with a mycorrhizal fungus to stimulate the roots of plants and / or stimulate the development of mycorrhizae, or the use of the fertilizing composition according to the invention to stimulate the roots of plants and / or stimulate the development of mycorrhizae.

[0054] According to another aspect of the invention, the invention relates to the use of the fertilizing composition according to the invention for growing leafy vegetables, fruit vegetables, root vegetables, cereals, flowers, ornamental crops, and vegetable crops, preferably for growing corn, potatoes, beetroot, rapeseed, sunflower, soybean, lettuce or grass. For example, using fertilizer when growing tuber plants like potatoes or leafy plants like lettuce.

[0055] EXAMPLES

[0056] Example 1 - Evaluation of the mycorrhization rate of corn roots.

[0057] The objective of this example was to evaluate the mycorrhization rate of corn roots, previously fertilized with struvite or with a classic phosphate fertilizer (here DAP (Di-Ammonium Phosphate)), all in combination with a mycorrhizal fungus (Asteria product from the company INOCULUMplus)).

[0058] [Table 1]

[0059] Table 1: Fertilizer application rates in kilograms per hectare (kg / ha). *Since DAP contains twice as much phosphate as struvite, the C2 and D1 application rates have equivalent phosphate concentrations.

[0060] Each fertilizer blend was prepared in granular form and tested in growing trays (0.24m2) containing 10 corn seeds evenly distributed. The substrate used consisted of a mixture of aquarium sand (1 / 3), terragreen (1 / 3) and soil substrate (1 / 3).

[0061] Methods C1 and C2 were applied at a rate of 0.6 g for the 0.24 m2 of the culture tanks. Method D1 was applied at a rate of 0.3 g in the culture tank.

[0062] To ensure a homogeneous distribution of the products, 1 L of 100x concentrated substrate was made upstream (with 60g of fertilizer for methods C1 and C2; and 30g of fertilizer for method D1). The total volume in the tanks being 18L, 180ml of the concentrated inoculated substrate was added to the remaining 17,820L of substrate.

[0063] As the products are usually applied as close as possible to the seed, the 180 ml of concentrated substrate was applied by sprinkling on the seeds over the entire surface of the tray.

[0064] In addition to the methods mentioned above, a 'negative control' tank (no addition) and a 'positive control' tank (60g of 'Astreo' product in 11 of substrate; then, 180 ml of this concentrated substrate distributed as a mixture near the seeds) were set up.

[0065] Germination rates were assessed at D+10.

[0066] After 7 weeks of culture, the root mycorrhization rates were obtained using the technique described by PHILLIPS and HAYMAN (1970). Three root samples were taken homogeneously and randomly from each culture tank. For each sample, thirty fragments per modality taken at random were mounted between slides and coverslips and observed under a microscope.

[0067] The estimation of the mycorrhization rate refers to the methodology described by TROUVELOT et al (1986).

[0068] [Table 2] Table 2: Analysis results.

[0069] Germination rates at D+10 varied from 70% (modality D1) to 100% (Negative control and modality C1) depending on the modalities.

[0070] At D+20, a clear difference in growth and leaf color (paler) was already observed between the negative control (12 cm height on average) and the other modalities (16 cm height on average). Modalities C1, C2 and D1 took the advantage in terms of plant growth over the "positive control" modality after 4 weeks of culture. A nitrogen deficiency was observed in the "negative control" modality after 3 weeks of culture; in the "positive control" modality after 4 weeks of culture; in modalities C1, C2 and D1 after 5 weeks of culture.

[0071] [Table 3] Table 3: Average mycorrhization rates of corn plants for the different methods tested. F% corresponds to the percentage of mycorrhizal roots; M% corresponds to the percentage of colonization inside the roots (M% = 0% means partial colonization of the roots; M% = 100% means that the fungus has completely colonized the root fragment observed); a% corresponds to the percentage of arbuscules observed (the higher a%, the more the fungus is permanently established in the roots).

[0072] After 7 weeks of culture, the evaluation of the root mycorrhization rate showed fungal structures of mycorrhizal fungi in the “positive control” modalities, C1 and C2 (Table 3).

[0073] The highest rates were observed in the "positive control" modality (F% = 42.8%). For modalities C1 and C2, F% values ​​lower than 10% were obtained. However, arbuscules (a% between 3.25% and 17.50%), as well as vesicles were observed in these samples, indicating a lasting implantation of the fungus(s) in the roots.

[0074] No mycorrhization was observed for sample DAP (D1).

[0075] Surprisingly, mycorrhization was therefore observed for fertilizer compositions comprising struvite, unlike those comprising DAP.

Claims

Claims

1. Fertilizer composition promoting the development of mycorrhizae comprising struvite and a mycorrhizal fungus.

2. Fertilizing composition according to claim 1, characterized in that it comprises between 5 and 99.9% by weight of struvite and between 0.1% and 15% by weight of a mycorrhizal fungus.

3. Fertilizing composition according to any one of claims 1 to 2, characterized in that it is in powder form.

4. Fertilizing composition according to any one of claims 1 to 2, characterized in that it is in the form of an emulsion in water.

5. Fertilizing composition according to any one of claims 1 to 2, characterized in that it is in granulated form.

6. Combination of a fertilizing composition according to any one of claims 1 to 5 and another complementary fertilizer chosen from nitrogen fertilizers, potassium fertilizers, calcium fertilizers and amendments, trace elements, boric acid, leonardite, organic amendments and feldspar, as well as combinations thereof, and / or in association with one or more biostimulants chosen from the group consisting of amino acid hydrolysates, humic extracts, algae extracts, plant extracts, living microorganisms, microorganism extracts and combinations thereof.

7. Fertilizing composition according to claim 6 for use in powder form, characterized in that it is in powder form, in the form of an emulsion in water or in granulated form, preferably in granulated form.

8. A method of stimulating plant roots and / or stimulating the development of mycorrhizae comprising applying the fertilizing composition according to any one of claims 1 to 7 to or in said soil.

9. Method according to claim 8, characterized in that said fertilizing composition is applied at a rate of 2.5 to 500, 5 to 200 kg / ha, 10 to 100 kg / ha, preferably 15 to 50 kg / ha.

10. Use of struvite in combination with a mycorrhizal fungus to stimulate plant roots and / or stimulate the development of mycorrhizae.

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