Seed treatment using hydroswellable polymer

Abstract

The invention relates to the field concerning the treatment of plant material, particularly plant material for propagation or reproduction e.g. seeds. The method of the invention comprises the application, to all or part of the surface of plant material, of an aqueous dispersion comprising (a) particles of at least one water-swellable polymer and (b) at least one compound selected from among a mineral salt, organic salt, dispersant organic polymer and mixtures thereof. The invention also relates to this treated plant material and to use thereof for cultivating or producing a plant.

Claims

1. A method for treating a plant material comprising applying an aqueous dispersion to all or part of the surface of the plant material, wherein the aqueous dispersion comprises: (a) particles of at least one water-swellable polymer that maintains a water absorption capacity greater than 10 times its volume; and (b) at least one equilibrating agent selected from the group consisting of a mineral salt, an organic salt, a dispersant organic polymer, and mixtures thereof; and wherein the water-swellable polymer is applied to the plant material in non-hydrated form.

2. The method according to claim 1, wherein the plant material is propagation plant material or reproduction plant material.

3. The method according to claim 1, wherein the water-swellable polymer is derived from at least one water-soluble monomer comprising at least one double ethylenic bond.

4. The method according to claim 1, wherein the particles of the aqueous dispersion have a mean diameter ranging from 0.1 to 1 000 μm.

5. The method according to claim 1, wherein the aqueous dispersion comprises 5 to 60% by weight of water-swellable polymer.

6. The method according to claim 1, wherein the aqueous dispersion comprises at least one equilibrating agent (b) selected from the group consisting of: mineral or organic salts comprising at least one anion selected from the group consisting of sulfates, dihydrogen phosphates, phosphates, and halides; mineral or organic salts comprising at least one cation selected from the group consisting of sodium, potassium, ammonium, magnesium, calcium, and aluminium; mixtures of at least two of these salts; dispersant organic polymers having a molecular weight ranging from 500 to 100 000 g.Math.mol.sup.−1; dispersant organic polymers selected from the group consisting of anionic, cationic, and amphoteric polymers and copolymers; and polymers or copolymers based on acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid and the salts thereof, or acrylamide.

7. The method according claim 1, wherein the aqueous dispersion comprises: 5 to 45% by weight of mineral salt or organic salt; or less than 30% by weight of dispersant organic polymer.

8. The method according to claim 1, wherein application of the aqueous dispersion to the plant material is obtained by coating, dipping, spraying or daubing.

9. The method according to claim 1, wherein the aqueous dispersion further comprises at least one substance of agronomic interest or at least one substance allowing improved development or growth of the plant material.

10. The method according to claim 1 further comprising: application of a binding agent selected from the group consisting of polyvinyl alcohols (PVOH), polyvinyl acetates (PVAc), polyacrylamides, polyacrylates, polymethacrylates, acrylamide/acrylate copolymers, acrylamide/methacrylate copolymers, polyvinylpyrrolidones (PVP), vinylpyrrolidone/dimethylaminoethylmethacrylate copolymers, vinylpyrrolidone/styrene copolymers, vinylpyrrolidone/vinylacetate copolymers, cellulose derivatives, natural gums, clays, graphite, talc, and la silica, before or simultaneously with application of the dispersion to the plant material; application of a film-forming or film-coating agent, selected from the group consisting of polyvinylpyrrolidones (PVP), vinylpyrrolidone/styrene copolymers, vinylpyrrolidone/vinylacetate copolymers, vinylpyrrolidone/dimethylaminoethylmethacrylate copolymers, polyacrylamides, acrylamide/acrylate copolymers, acrylamide/methacrylate copolymers, methylvinylether/maleic anhydride copolymers, polyurethanes, polyvinyl alcohols, polyvinyl acetates, cellulose derivatives, alginates, and natural gums, simultaneously with or after application of the dispersion to the plant material; or application of at least one substance of agronomic interest or at least one substance allowing improved development or growth of the plant material selected from the group consisting of fertilizers, hormones, micro-organisms, mycorrhizas, growth stimulators, growth regulators, phytosanitary products, fungicides, insecticides, and safeners before, simultaneously with, or after application of the dispersion to the plant material.

11. The method according to claim 1, wherein said method further comprises: prior preparation of the aqueous dispersion comprising: (a) particles of at least one water-swellable polymer that maintains a water absorption capacity greater than 10 times its volume; (b) at least one equilibrating agent selected from the group consisting of a mineral salt, organic salt, dispersant organic polymer and mixtures thereof; by polymerization of the water-swellable polymer directly in an aqueous solution comprising at least one equilibrating agent selected from the group consisting of a mineral salt, organic salt, dispersant organic polymer, and mixtures thereof; or via simple mixing of compounds a) and b); and drying the plant material after application of the dispersion.

12. A method of using the plant material prepared according to the method of claim 1 comprising cultivating or producing a plant derived from said plant material.

Description

EXAMPLES

(1) TABLE-US-00001 Table of the compositions used in the different examples Composition Description A Mixture containing 33 weight % of water-swellable (comparative) polymer in the form of a cross-linked acrylamide and sodium acrylate powder, of particle size less than 200 μm, and 67 weight % of fine graphite powder. The micronized graphite is a non-aqueous binding agent. B Aqueous dispersion containing 25 weight % of water- (of the invention) swellable polymer of cross-linked acrylamide and sodium acrylate, of particle size less than 15 μm. This aqueous dispersion contains a total of 43 weight % dry matter including the water-swellable polymer, ammonium sulfate and dispersant polymers. C Mixture containing 99.35 weight % water and 0.65 (comparative) weight % of water-swellable polymer in the form of a copolymer powder of cross-linked acrylamide and sodium acrylate, previously screened to 200 μm in the dry state (its weight absorption capacity is 150 times in this water). In this composition the water-swellable polymer is fully hydrated in slight excess water. D Composition containing the same ingredients as (comparative) composition C but here the water-swellable polymer is only partly hydrated. The composition contains 99% water and 1% water-swellable polymer (by weight). E Water-swellable polymer of cross-linked acrylamide (comparative) and sodium acrylate in the form of an inverse water- in-oil emulsion. The emulsion contains 30% water- swellable polymer.

Example 1

(2) Case 1) 0.5 g of composition A was applied to 50 g of common wheat seeds, in a weight ratio of 1:100. To prevent hazardous exposure to dust, application was performed under a suction hood, in a stainless-steel rotating drum of diameter 20 cm, and the end product (seeds coated with composition A) was subjected to a drying step 5 minutes at 40° C.

(3) Case 2) 11.6 g of composition B were applied to 50 g of common wheat seeds, the composition dry matter/seed ratio being 1:10. The application method was the same as described for Case 1.

(4) In each case, to evaluate the quality of adhesion of the compositions to the seeds, the whole mixture obtained was placed on a sieve of mesh size 300 μm, subjected to vibration of amplitude 1.5 mm/“g” (1 g=9.81 m/s.sup.2) for 1 minute (Retsch AS 200 Control Sieve Shaker), to generate attrition and abrasion. The percentage of free fine particles was inferred from the quantity passing through the 300 μm sieve relative to the weight of water-swellable polymer initially applied (dry matter)

(5) Results:

(6) TABLE-US-00002 Weight of applied water- swellable polymer (g) Percent free fines (%) Case 1 0.165 75 Case 2 2.9 0.8

(7) According to the method of the invention (Case 2) it is possible, in more reliable manner, to apply larger quantities of water-swellable polymer whilst obtaining better properties of coating adhesion to the seeds than the method in Case 1.

Example 2

(8) Case 1) 50 g of composition C were applied to 50 g of common wheat seeds in a stainless-steel rotating drum of diameter 20 cm. The system required a minimum drying time of 25 min at 40° C. to obtain a dry coating. On completion of the method, under visual observation, the rate of coating of the surface of seeds with the coating product was estimated to be less than 5%.

(9) Case 2) 50 g of composition D were applied to 50 g of common wheat seeds in a stainless-steel rotating drum of diameter 20 cm. The system required a minimum drying time of 20 min at 40° C. to obtain a dry coating. On completion of the method under visual observation, the rate of coating of the surface of the seeds with the coating product was estimated to be less than 10%.

(10) Case 3) 50 g of seeds were treated with composition B in identical manner to Example 1, Case 2, i.e. 11.6 g of composition B. On completion of the method, under visual observation, the rate of coating of the seeds with the coating product was estimated to be higher than 90%.

(11) In comparison, the coating methods of Cases 1) and 2) are much more restrictive for persons skilled in the art since they require the handling of large volumes of compositions C and D and involve a particularly lengthy drying step to remove the large amount of water used. In addition, the final quantity of applied polymer is low compared with the product obtained in Case 3) representing the method of the invention.

Example 3

(12) Case 1) 50 g of common wheat seeds were treated with 1 weight % of composition E. Application was carried out in a stainless-steel rotating drum of diameter 20 cm. The product was subjected to a drying step of 10 min/40° C.

(13) Case 2) 50 g of common wheat seeds were treated with 1 weight % of composition B, following the same steps as described for Case 1.

(14) Case 3) 50 g of common wheat seeds were treated with 6 weight % of composition E following the same steps as described for Case 1.

(15) Case 4) 50 g of common wheat seeds were treated with 6 weight % of composition B following the same steps as described for Case 1.

(16) The flowability of the treated seeds was tested using a cone having an orifice of diameter smaller than 1.5 cm. The seeds were first loaded into the cone. The lower orifice was initially closed at the time of loading then opened at time t.sub.0 to evaluate the capacity of the seeds to flow through the orifice. The test was considered to be successful if the entirety of the load flowed through the orifice after t.sub.0+30 seconds.

(17) Results:

(18) TABLE-US-00003 Test success rate* Case 1 65% Case 2 90% Case 3  0% Case 4 35% *For each case, a mean of 20 tests was calculated,

(19) For equivalent dosages of coating composition, the flowability of the seeds treated according to the method of the invention (Cases 2 and 4) was significantly better than for Cases 1 and 3, this being a definite advantage for persons skilled in the art.