Fertilizing composition that promotes 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

Title of the invention: Fertilizing composition promoting the development of mycorrhizae technical field

[0001] The present invention relates to a fertilizing composition promoting the development of mycorrhizae.

[0002] STATE OF THE ART

[0003] 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 medium. To establish the mycorrhiza, the fungus colonizes the plant's root system with its mycelium, composed of hyphae (vegetative filamentous elements). The network of hyphae extends well beyond the plant's roots and can therefore access the relatively immobile phosphorus in the soil from deeper layers. In addition to the nutrient advantage, mycorrhizae offer other benefits: improved resistance to pathogens, insects, drought, and stress, as well as a positive impact on soil aggregation.Consequently, in order to promote sustainable agriculture that consumes less mineral fertilizer in light of current climate challenges, promoting the development of mycorrhizae is of paramount importance.

[0004] However, mycorrhizae are virtually never taken into account in 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 their disappearance is the use of conventional phosphate fertilizers such as DAP. When these fertilizers hydrolyze, the crude phosphoric acid attacks the hyphae, leading to their destruction. Furthermore, the application of inorganic phosphate greatly reduces the plant's incentive to feed the mycorrhizal fungi, since it can access this resource itself.

[0005] Phosphate is used extensively in the form of chemical fertilizers in our agriculture. Every 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. In this context, it is also imperative to find solutions to limit the use of non-renewable phosphate fertilizers.

[0006] In view of the foregoing, there is therefore a need for a fertilizing composition based on renewable phosphate fertilizers promoting the development of mycorrhizae.

[0007] DESCRIPTION OF THE INVENTION

[0008] The inventors have surprisingly determined that the use of struvite in combination with at least one mycorrhizal fungus makes it possible to ensure and improve plant nutrition by increasing the phosphorus content in plants while promoting the development of mycorrhizae, and this contrary to the use of conventional phosphate fertilizers such as DAP (see example 1).

[0009] According to one aspect of the present invention, a fertilizing composition promoting the development of mycorrhizae is proposed, comprising struvite and at least one mycorrhizal fungus.

[0010] 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.

[0011] Struvite is a mineral of the hydrated phosphate family, namely a double ammonium and magnesium phosphate hexahydrate with the chemical formula NH4MgPO4. It is a mineral naturally present in manure and guano, as well as in pathologies of the urinary tract and renal tract.

[0012] 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.

[0013] Struvite poses a problem in wastewater treatment plants due to the accumulation of its crystals in the pipes and a reduction in water flow. Currently, numerous methods exist to control struvite nucleation in wastewater treatment plants and reduce the amount of phosphate entering water bodies.

[0014] There is considerable interest in recycling phosphorus (P) in the form of struvite for environmental, economic, and commercial reasons. Rather than generating waste to be disposed of, the recovered phosphate in the form of struvite can be advantageously used as a fertilizer and also deserves the designation "renewable fertilizer" because of its source.

[0015] An additional advantage of struvite is its limited solubility. The fertilizer dissolves over time to provide nutrients at a rate that plants can use. Highly soluble fertilizers tend to release nutrients at a faster rate than plant absorption, resulting in fertilizer waste and negative environmental impacts.

[0016] 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.

[0017] Mycorrhizal fungi are fungi that have the unique characteristic of entering into a symbiotic relationship with plant roots (a mutually beneficial agreement between the two organisms). A mycorrhizal fungus is further characterized by being a benign soil fungus that is advantageous to plants. The mycorrhizal fungus cannot extract the carbon compounds necessary for its growth and development from the soil. Therefore, the mycorrhizal fungus utilizes the carbon compounds produced through its symbiosis with the plant, which produces these compounds by photosynthesis. Among other things, the mycorrhizal fungus can absorb nutrients that are difficult for plants to assimilate. These include phosphate compounds, nitrogen compounds, and metal ions, notably potassium, calcium, and magnesium, as well as trace elements that bind in poorly soluble complexes.The plant benefits from this symbiosis because it can more easily access nutrients through the mycorrhizal fungus. This mutualistic cooperation results in a self-sustaining system, but also leads to a synergistic effect. Indeed, the mycorrhizal fungus is able to absorb more nutrients, and the plant experiences improved growth and development, allowing more mycorrhizal fungi to live alongside the plant. This cooperation is therefore long-term and possible without intensive external management.

[0018] In a preferred embodiment, the mycorrhizal fungus is chosen 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.

[0019] Arbuscular mycorrhizal fungi are characterized by their 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 to which the function of nutrient storage is attributed. Arbuscular mycorrhizal fungi form underground fruiting bodies. Preferred embodiments include, but are not limited to, Glomus mosseae and Glomus intraradices.

[0020] Ecto-mycorrhizal fungi do not form arbuscules and vesicles. In In contrast, ectomycorrhizal fungi develop around and within roots, where they form a specific structure called a "Hartig net." The fungal threads that form the Hartig net develop intercellularly. As they grow around the roots, the ectomycorrhizal fungi form a layer around the root. The color and shape of this layer can vary depending on the species of ectomycorrhizal fungi. Within the Hartig net, there is an exchange of nutrients, particularly nitrogen, phosphate, and carbon. Ectomycorrhizal fungi form aerial fruiting bodies. Preferred embodiments include, but are not limited to, Laccaria laccata, Boletus edulis, Cantharellus cibarius, and Paxillus involutus.

[0021] Ecto-mycorrhizal fungi are characterized in that they do not form arbuscules and vesicles and develop intracellularly within root cells. Ecto-mycorrhizal fungi also form a so-called "salted net," but this is distinctly thinner than with ecto-mycorrhizal fungi. Ecto-mycorrhizal fungi can form aerial fruiting bodies. Preferred embodiments relate to, but are not limited to, the species Tuber, Tricharlna, and Wilcoxina.

[0022] Ericoid mycorrhizal fungi are characterized by intracellular growth within root cells. Ericoid mycorrhizal fungi do not form a layer, a so-called "Hartig" net, 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.

[0023] 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 a particularly advantageous effect due to the compatibility 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 selected plant species leads to an advantage when using different species or different types of mycorrhizal fungi.

[0024] The inventors have surprisingly determined that the use of struvite in combination with at least one mycorrhizal fungus makes it possible to ensure and improve plant nutrition while promoting the development of mycorrhizae, contrary to the use of conventional phosphate fertilizers such as DAP (see example 1).

[0025] According to one embodiment, the fertilizing composition further comprises at least two trace elements, at least one secondary element, and at least one clay.

[0026] According to one embodiment, the fertilizer 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.

[0027] At least the 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 The trace element is zinc oxide.

[0028] 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, potassium sulfate, monoammonium phosphate, potassium chloride, calcium chloride, calcium sulfate, magnesium sulfate, magnesium chloride, sodium chloride, diammonium phosphate, ammonium chloride, monocalcium phosphate, dicalcium phosphate, tricalcium phosphate, single superphosphate, triple superphosphate, zinc sulfate, iron sulfate, calcium phosphate, monopotassium phosphate, sodium nitrate, magnesium nitrate, the 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 ammonium sulfate.

[0029] 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.

[0030] According to a preferred embodiment of the invention, the fertilizer 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.

[0031] According to one embodiment, the fertilizer composition according to the invention is in the form of a powder, an emulsion in water, or in granular form, preferably in granular form.

[0032] 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.

[0033] According to one embodiment, the fertilizing composition according to the invention is included in or consists of the core of a granular fertilizer.

[0034] 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.

[0035] The fertilizer composition according to the invention may further comprise or be combined with other components selected for example from binders, additives, fillers, fillers and minerals.

[0036] The fertilizer composition may include or be combined with, but 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 and magnesium sulfate, potassium sulfate, sodium nitrates, magnesian limestone, magnesia, urea, urea-formaldehyde, urea ammonium nitrate, urea sulfur-coated urea, polymer-coated urea, isobutylidene diurea, K2SO4-2MgSO4, kainite, sylvinite,kieserite, Epsom salts, elemental sulfur, marl, crushed oyster shells, fishmeal, oilseed cakes, fish manure, flour of, blood, phosphate rock, superphosphates, 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 fertilizer composition according to the invention.

[0037] According to another aspect of the invention, the fertilizing composition according to the invention is combined with at least one other complementary fertilizer selected from nitrogen fertilizers, potassium fertilizers, phosphate fertilizers, binary (NP,PK) and ternary (NPK) fertilizers and their combinations, and alternatively in association with calcium amendments, trace elements, boric acid, leonardite, organic amendments and feldspar, one or more biostimulants selected from the group consisting of amino acid hydrolysates, humic extracts, seaweed extracts, plant extracts, live microorganisms, microorganism extracts and their combinations.

[0038] Said combination of the fertilizer 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.

[0039] According to one embodiment, the sugars of said at least one supplementary fertilizer are selected from mono- and di-saccharides, preferably sucrose, fructose, trehalose, glucose, arabinose, maltose, and mixtures thereof.

[0040] According to one embodiment, the amino acids of said at least one supplementary fertilizer are selected 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.

[0041] According to one embodiment, the organic acids of said at least one supplementary fertilizer are selected from lactic acid, succinic acid, oxalic acid, gluconic acid, threonic acid, fumaric acid, syringic acid and mixtures thereof.

[0042] According to one embodiment, the diamines and polyamines of said at least one supplementary fertilizer are selected from cadaverine, putrescine, spermidine, the Spermine and their mixtures.

[0043] 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 at a rate of 10 to 60% by weight.

[0044] 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.

[0045] 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.

[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 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.

[0047] According to an 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 at a rate 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 complexing agents humate, citrate, gluconate, heptagluconate and amino acids or with chelating agents ethylenediaminetetraacetic acid, ethylenediamine-di(o-hydroxyphenylacetic acid, diethylenetriaminepentaacetic acid.

[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 organic amendment is present at a rate of 5 to 90% by weight and is chosen from cattle, sheep, pig, mink, rabbit and chicken manure.

[0049] 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.

[0050] According to one embodiment, the live microorganisms or extracts of microorganisms are chosen from the families of Thiorhodaceae, Athiorhodaceae, Chlorobacteriaceae, Nitrobacteraceae, preferably of the genus Nitrosomonas or Nitrobacter, Thiobacteraceae, preferably of the genus Thiobacillus, Methanomonadaceae, preferably of the genera Hydrogenomonas, Carboxydomonas or Methanomonas, Caulobacterium, Siderocapsaceae, Pseudomonas, preferably of the genera Pseudomonas, Xanthomonas, Acetobacter or Azotomonas, Spirillaceae, preferably of the genera Vibrio, Cellvibrio, Cellfalcicula, Desulfovibrio or Spirillum, Azotobacteria, preferably of the genera Azotobacter, Beijerinckia or Derxia, Rhizobacteria, preferably of the genera Rhizobium, Chromobacterium or Agrobacterium, Achrobacterium, preferably of the genera Achromobacter or Flavobacterium, Enterobacteriaceae, preferably of the genera Escherichia, Proteus, Aerobacter or Serratia, Micrococcaceae, preferably of the genera Micrococcus or Sarcina, Brevibacteria, preferably of the genus Brevibacterium, Lactobacillus, preferably of the genera Streptococcus, Leuconostoc or Lactobacillus, Corynebacteria preferably of the genus Corynebacterium, Cellulomonas or Arthrobacter, Bacillacea preferably of the genus Bacillus or Clostridium, and their mixtures.Preferably, live microorganisms or extracts of microorganisms are chosen from the species Pichia guilliermondii, Azo-tobacterchroococcum, Azotobacter vinelandii, Azospirillum lipoferum, Bacillus megaterium, Bacillus aryabhattai, Bacillus amiloliquefaciens, Bacillus licheniformis and Oceanobacillus picturae, and mixtures thereof.

[0051] According to another aspect of the invention, the invention relates to a method of stimulating plant roots and / or 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.

[0052] According to another aspect of the invention, the invention relates to the use of struvite in combination with a mycorrhizal fungus to stimulate plant roots and / or stimulate the development of mycorrhizae, or the use of the fertilizing composition according to the invention to stimulate plant roots and / or stimulate the development of mycorrhizae.

[0053] According to another aspect of the invention, the invention relates to the use of the fertilizer composition according to the invention for the cultivation of leafy vegetables, fruit vegetables, root vegetables, cereals, flowers, ornamental crops, and vegetable crops, preferably for the cultivation of maize, potatoes, beets, rapeseed, sunflowers, soybeans, lettuce or turf. For example, the use of fertilizer for growing tuberous plants such as potatoes or leafy plants such as lettuce.

[0054] EXAMPLES

[0055] Example 1 - Evaluation of the mycorrhization rate of maize roots.

[0056] The objective of this example was to evaluate the mycorrhization rate of maize roots, previously fertilized with struvite or with a phosphate fertilizer. classic (here DAP (Di-Ammonium Phosphate)), all in combination with a mycorrhizal fungus (Asteria product from the company INOCULUMplus)).

[0057] [Tables 1] Struvite (kg / ha) DAP (kg / ha) Mycorrhizal inoculum (kg / ha) % of mycorrhizal inoculum recommended by the supplier (1 kg / ha) Method according to the invention (Cl) 25 kg 1 kg 100% Method according to the invention (C2) 25 kg 250 g 25% DAP (Dl) 12.5 kg* 250 g 25%

[0058] Table 1: Fertilizer application rates in kilograms per hectare (kg / ha). *Since DAP contains twice as much phosphate as struvite, modalities C2 and DI have equivalent phosphate concentrations.

[0059] Each fertilizer mixture was prepared in granular form and tested in culture trays (0.24 m²) 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).

[0060] Modalities C1 and C2 were applied at a rate of 0.6 g per 0.24 m² of culture trays. Modality DI was applied at a rate of 0.3 g in the culture tray.

[0061] To ensure a homogeneous distribution of the products, 100 ml of concentrated substrate was prepared beforehand (with 60 g of fertilizer for treatments C1 and C2; and 30 g of fertilizer for treatment D1). Since the total volume in the tanks was 18 L, 180 ml of the concentrated inoculated substrate was added to the remaining 17.82 L of substrate.

[0062] Since the products are usually applied as close as possible to the seed, the 180 ml of concentrated substrate were applied by sprinkling over the seeds across the entire surface of the tray.

[0063] In addition to the above-mentioned modalities, a 'negative control' tray (no addition) and a 'positive control' tray (60g of 'Astreo' product in 11 of substrate; then, 180 ml of this concentrated substrate distributed in a mixture near the seeds) were set up.

[0064] Germination rates were evaluated at J+10.

[0065] After 7 weeks of culture, root mycorrhization rates were obtained according to the technique described by PHILLIPS and HAYMAN (1970). Three samples of Roots were collected homogeneously and randomly from each culture tray. For each sample, thirty randomly selected fragments per treatment were mounted between slides and coverslips and observed under a microscope.

[0066] The estimation of the mycorrhization rate refers to the methodology described by TROUVELOT et al (1986).

[0067] [Tables2] Treatment Type Number of Germinated Grains Germination Rate (%) Negative Control 10 100% Positive Control 8 80% Cl 10 100% C2 9 90% Dl 7 70% Table 2: Analysis results.

[0068] Germination rates at J+10 varied from 70% (Dl modality) to 100% (Negative control and Cl modality) depending on the modality.

[0069] At day 20, a clear difference in growth and leaf color (paler) was already observed between the negative control (12 cm average height) and the other treatments (16 cm average height). Treatments Cl, C2, and Dl showed superior plant growth compared to the positive control treatment after 4 weeks of cultivation. Nitrogen deficiency was observed in the negative control treatment after 3 weeks of cultivation; in the positive control treatment after 4 weeks of cultivation; and in treatments Cl, C2, and Dl after 5 weeks of cultivation.

[0070] [Tables3] Negative control Positive control Cl C2 Dl F% 0 42.80 6.67 7.78 0 M% 0 7.66 0.11 0.12 0 A% 0 8.89 11.90 17.50 0 Table 3: Average mycorrhization rates of maize plants for the different modalities tested.

[0071] 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 observed root fragment); a% corresponds to the percentage of arbuscules observed (the higher the percentage, the more permanently the fungus is established in the roots).

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

[0073] The highest rates were observed in the "positive control" treatment (F% = 42.8%). For treatments C1 and C2, F% values ​​below 10% were obtained. However, arbuscules (a% between 3.25% and 17.50%) and vesicles were observed in these samples, indicating a persistent presence of the fungus(ies) in the roots.

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

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

Claims

Demands

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

2. Fertilizing composition according to claim 1, characterized in that it is in powder form.

3. Fertilizing composition according to claim 1, characterized in that it is in the form of an emulsion in water.

4. Fertilizing composition according to claim 1, characterized in that it is in granular form.

5. Combination of a fertilizing composition according to any one of claims 1 to 4 and another complementary fertilizer selected from nitrogen fertilizers, potassium fertilizers, calcium fertilizers and amendments, trace elements, boric acid, leonardite, organic amendments and feldspar, and combinations thereof, and / or in association with one or more biostimulants selected from the group consisting of amino acid hydrolysates, humic extracts, seaweed extracts, plant extracts, live microorganisms, microorganism extracts and combinations thereof.

6. Fertilizing composition according to claim 5 for use in powder form, characterized in that it is in powder form, in the form of an emulsion in water or in granular form, preferably in granular form.

7. A method for stimulating plant roots and / or stimulating the development of mycorrhizae comprising applying the fertilizing composition according to any one of claims 1 to 6 on or in said soil.

8. The method according to claim 7, characterized in that said fertilizer 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.

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