This invention relates to a rice seed coated with silica particles, to a process for preparing said coated rice seed, and to a method of improving the floating tolerance of rice seed. More particularly, the invention relates to direct sown rice seed.

Rice planting can generally be divided into two categories: direct sown rice, which uses seeds, and transplanted rice, which involves seedlings. Direct sown rice can be planted into a flooded field or a field without excess water. In flooded fields, the soil is covered with a layer of water, typically from 3-10 cm deep. Rice is either sown onto the soil surface or drilled into the upper layer of the soil. Whether rice seeds are sown upon the surface or drilled into the soil, either way the seed is submerged in water.

When the rice seed for direct sowing of flooded field is drilled into the soil surface, this is typically done to a depth of approximately 0.5-1 cm. It is standard practice to use pregerminated rice when drilling into the soil layer. To get the rice to germinate, it is soaked in water at about 15°C for about 4 to 6 days. Optionally a seed can be coated with agrochemicals before or after the soaking step, before sowing. Sowing practice can also be done by planting on the soil surface with a planting depth of approximately 0-0.5 cm. In this case, rice seed sown in flooded field may not always be covered by soil.

However, rice seeds are usually floated and finally flushed away through irrigated water at the flooded paddy field. Hence, there remains a need in the art for improving the water immersion of rice seeds, especially for direct sown rice seeds.

Therefore, the aim of the present invention is to overcome the problems of the prior art techniques by proposing a new coated rice seed having better floating tolerance, while guaranteeing a good hydrophilicity. More particularly, a better floating tolerance means that the floating property of the rice seed is significantly decreased, or even avoided, especially with rice seed sown in flooded field.

To this end, an object of the present invention relates to a coated rice seed comprising at least an external coating of silica particles, said external coating surrounding the rice seed. More preferably, this invention relates to a coated rice seed comprising at least an external coating, said external coating surrounding the rice seed, characterized in that said external coating is obtained by applying silica particles in solid form. In a preferred embodiment, the external coating can be the outermost coating of the rice seed.

The coated rice seed according to the invention presents advantageous an improved floating tolerance, especially for direct sown rice seed in flooded field, that provides a better accuracy and/or homogeneity when sowing. The coated rice seed also guarantees a good hydrophilicity. Furthermore, the process for preparing said coated rice seed is easy and rapid to implement.

In the present invention, the expression “coated rice seed(s)” means:

- uncoated rice seed(s) onto which is applied said external coating, or

- rice seed(s) coated with at least one coating different from said external coating, onto which is applied said external coating.

More particularly, rice seeds in the present invention can be non-germinated rice seeds, optionally primed or pre-germinated.

As used herein “rice” refers to the cereals scientifically classified as rice such as Oryza glaberrima, O. nivara. O. rufipogon and O. sativa and also plants which are commonly referred to as rice for example Zizania spp.

The rice discussed herein is to be understood as being those crops which are naturally occurring, obtained by conventional methods of breeding, or obtained by genetic engineering. They include crops which contain so-called output traits (e.g. improved storage stability, higher nutritional value and improved flavour).

Rice crops are to be understood as also including those crops which have been rendered tolerant to herbicides like bromoxynil or classes of herbicides such as ALS-, EPSPS-, GS-, HPPD- and PPO-inhibitors. Crops are also to be understood as being those which naturally are or have been rendered resistant to harmful insects. This includes plants transformed by the use of recombinant DNA techniques, for example, to be capable of synthesizing one or more selectively acting toxins, such as are known, for example, from toxin-producing bacteria. Examples of toxins which can be expressed include 5-endotoxins, vegetative insecticidal proteins (Vip), insecticidal proteins of bacteria colonizing nematodes, and toxins produced by scorpions, arachnids, wasps and fungi. Crops or seed material thereof can also be resistant to multiple types of pests (so-called stacked transgenic events when created by genetic modification). For example, a plant can have the ability to express an insecticidal protein while at the same time being herbicide tolerant.

As used herein, the term “seed” refers to any suitable plant propagation material and specifically includes seeds in the strict sense as well as vegetative material of plants such as synthetic seeds created using tissue culture.

According to the present invention, the silica particles can be precipitated silica particles or fumed silica particles.

The silica particles can have an average diameter range from 1 to 500 pm, and more preferably from 5 to 30 pm. This dimension can be determined conventionally by methods that are well known to the person skilled in the art, such as for example by laser diffraction.

The silica particles can have a specific surface area range from 10 to 500 m ² /g, and more preferably from 50 to 400 m ² /g.

Specific examples of silica particles can be selected among silica clay, silica gel, white carbon, aerosol, and the like. Preferably, white carbon is used. The silica particles according to the present invention comprises more than 50% by weight of silica (SiCh), preferably at least 70% by weight of silica, preferably at least 80% by weight of silica, preferably at least 90% by weight of silica, and more preferably at least 95% by weight of silica, over the total weight of the silica particles.

Silica particles can be commercially available products such for example those from Evonik under the following trade names:

- Carplex: Carplex #67, Carplex #80, Carplex #80QM, CArplex#101, Carplexl l20, Carplex#101, Carplex BS-303, Carplex BS-306, Carplex BS-308N, Carplex BS-510BX, Carplex CS-5, Carplex CS-7, Carplex CS-8, Carplex BS 312 AM, CarplexFPS-1, CarplexFPS- 101, CarplexFPS-500, CarplexXR;

- SIPRENAT: SIPRENAT 22, SIPRENAT 22S, SIPRENAT 22 LS, SIPRENAT 25, SIPRENAT 33, SIPRENAT 35, SIPRENAT 50, SIPRENAT 50S, SIPRENAT 101M, SIPRENAT 120, SIPRENAT 160, SIPRENAT 218, SIPRENAT 236, SIPRENAT 238, SIPRENAT 268, SIPRENAT 288, SIPRENAT 298, SIPRENAT 303, SIPRENAT 306, SIPRENAT 310, SIPRENAT 320, SIPRENAT 320DS, SIPRENAT 325C, SIPRENAT 350, SIPRENAT 360, SIPRENAT 383DS, SIPRENAT 622LS, SIPRENAT 500LS, SIPRENAT 2200, SIPRENAT BG-2, SIPRENAT FPS-5, SIPRENAT 622 S, SIPRENAT 680, SIPRENAT FPS-1, SIPRENAT 11PC, SIPRENAT 22PC, SIPRENAT 2200PC;

- AEROSIL: AEROSIL 50, AEROSIL 90G, AEROSIL 130, AEROSIL 200, AEROSIL 200CF, AEROSIL 200V, AEROSIL 200 FAD, AEROSIL, 300, AEROSIL 300CF, AEROSIL, 380, AEROSIL 0X50, AEROSIL TT600.

In the present invention, the weight ratio of silica particles to rice seeds can range from 1 g to 20 g of silica particles, and more preferably from 1 g to 10 g of silica particles, over 1 kg of rice seeds.

In a particular embodiment, the coated rice seed can further comprise at least a first coating of a treatment composition surrounding the rice seed, said first coating being surrounded by said external coating. The treatment composition can comprise an oxygen generator, and optionally can further comprises at least one ingredient selected among a seed weight increaser, a water-insoluble binder, a water-soluble binder, and any mixtures thereof.

The oxygen generator can be any compound or composition which creates or reacts with the local environment to create oxygen. For example, the oxygen generator can be selected among magnesium peroxide (MgCL), strontium peroxide (SrCL), zinc peroxide (ZnCL), calcium peroxide (CaCL), and any mixtures thereof.

The seed weight increaser can be any compound or composition which will increase the weight or density of a plant propagation material, especially a rice seed. In terms of amounts, one strives to increase by a sufficient amount to cause rice comprising the weight increaser to promptly settle onto the soil surface when soil-surface rice planting is performed. It will be apparent to skilled persons that the amount will necessarily vary depending on the planting conditions, rice seed variety and moisture content, and properties of the weight increaser. For example, the seed weight increaser can be selected among iron (Fe), quartz sand, barium sulfate, calcium carbonate, zinc oxide, iron oxide (Fe20s), and any mixtures thereof. The water-insoluble binder is well-known in the art, and can be more particularly a water-insoluble polymer, such as for example the one selected among polyacrylate adhesive, copolymer of vinyl acetate, vinyl versatate (VeoVA) and acrylate ester, copolymer of ethylene and vinyl acetate (EVA), polyurethane, polyvinyl acetate (PVAc), and any mixtures thereof.

The water-soluble binder is well-known in the art, and can be more particularly a water-soluble polymer, such as for example the one selected among polyvinyl alcohol, carboxymethyl cellulose (CMC), hydroxypropylmethyl cellulose (HPMC), polyvinyl pyrrolidone (PVP), and any mixtures thereof.

In a particular embodiment, the coated rice seed can further comprise at least a first coating of a treatment composition surrounding the rice seed, said first coating being surrounded by said external coating. The treatment composition can comprise an oxygen generator, and optionally can further comprises at least one ingredient selected among a seed weight increaser, a water-insoluble binder, a water-soluble binder, and any mixtures thereof.

The treatment composition according to the invention can comprise:

- an oxygen generator in an amount from 5 to 78% by weight, preferably from 20 to 55% by weight, and more preferably from 30-50% by weight, over the total weight of the treatment composition;

- a seed weight increaser in an amount from 20 to 80% by weight, preferably from 40 to 80% by weight, and more preferably from 50 to 70% by weight, over the total weight of the treatment composition;

- a water-insoluble binder, and more particularly a water-insoluble polymer, in an amount from 1 to 20% by weight, preferably from 10 to 20% by weight, and more preferably from 1 to 8% by weight, over the total weight of the treatment composition; and

- a water-soluble binder, and more particularly a water-soluble polymer, in an amount from 1 to 20% by weight, preferably from 10 to 20 % by weight, and more preferably from 3 to 7% by weight, over the total weight of the treatment composition. In a particular embodiment according to the present invention, the coated rice seed can further comprise at least a second coating of an agrochemical composition surrounding the rice seed. More preferably, said second coating can be surrounded by said external coating.

In a particular embodiment wherein the coated rice seed include the first coating of a treatment composition, the agrochemical composition can be applied simultaneously or separately with the treatment composition. More preferably, the second coating of an agrochemical composition can surround the first coating of a treatment composition. In a preferred embodiment, the first coating of a treatment composition and the second coating of an agrochemical composition can be surrounded by the external coating.

In the present invention, the agrochemical composition can include at least one agrochemical selected among fungicides, insecticides, bactericides, acaricides, nematicides, plant growth regulators, and any mixtures thereof. These agents may be provided as formulations comprising, inter alia, carriers, surfactants or application promoting adjuvants customarily employed in the art of formulation. The present invention is also suitable for use with other agrochemicals such as primers and safeners.

Examples of suitable agrochemicals include the following:

Insecticides such as benzoylureas, carbamates, chloronicotinyls, diacylhydrazines, diamides, fiproles, macrolides, neonicotinoids, nitroimines, nitromethylenes, organochlorines, organophosphates, organosilicons, organotins, phenylpyrazoles, phosphoric esters, pyrethroids, spinosyns, tetramic acid derivatives and tetronic acid derivatives.

Specific examples of preferred insecticides include thiamethoxam, clothianidin, imidacloprid, acetamiprid, dinotefuran, nitenpyram, thiacloprid, thiodicarb, aldicarb, carbofuran, furadan, fenoxycarb, carbaryl, sevin, ethienocarb, fenobucarb, chlorantraniliprole, cyantraniliprole, flubendiamide, spinosad, spinetoram, lambda-cyhalothrin, gamma- cyhalothrin, tefluthrin, fipronil, and sulfoxaflor.

Fungicides such as acycloamino acid fungicides, aliphatic nitrogen fungicides, amide fungicides, anilide fungicides, antibiotic fungicides, aromatic fungicides, arsenical fungicides, aryl phenyl ketone fungicides, benzamide fungicides, benzanilide fungicides, benzimidazole fungicides, benzothiazole fungicides, botanical fungicides, bridged diphenyl fungicides, carbamate fungicides, carbanilate fungicides, conazole fungicides, copper fungicides, dicarboximide fungicides, dinitrophenol fungicides, dithiocarbamate fungicides, dithiolane fungicides, furamide fungicides, furanilide fungicides, hydrazide fungicides, imidazole fungicides, mercury fungicides, morpholine fungicides, organophosphorous fungicides, organotin fungicides, oxathiin fungicides, oxazole fungicides, phenylsulfamide fungicides, polysulfide fungicides, pyrazole fungicides, pyridine fungicides, pyrimidine fungicides, pyrrole fungicides, quaternary ammonium fungicides, quinoline fungicides, quinone fungicides, quinoxaline fungicides, strobilurin fungicides, sulfonanilide fungicides, thiadiazole fungicides, thiazole fungicides, thiazolidine fungicides, thiocarbamate fungicides, thiophene fungicides, triazine fungicides, triazole fungicides, triazolopyrimidine fungicides, urea fungicides, valinamide fungicides, and zinc fungicides.

Specific examples of preferred fungicides include azoxystrobin, trifloxystrobin, fluoxastrobin, cy proconazole, difenoconazole, prothioconazole, tebuconazole, triticonazole, fludioxonil, thiabendazole, ipconazole, cyprodinil, myclobutanil, metalaxyl, metalaxyl-M (also known as mefenoxam), sedaxane, and penflufen.

Nematicides such as antibiotic nematicides, avermectin nematicides, botanical nematicides, carbamate nematicides, oxime carbamate nematicides, and organophosphorus nematicides.

Specific examples of preferred nematicides include abamectin, aldicarb, thiadicarb, carbofuran, carbosulfan, oxamyl, aldoxycarb, ethoprop, methomyl, benomyl, alanycarb, iprodione, phenamiphos (fenamiphos), fensulfothion, terbufos, fosthiazate, dimethoate, phosphocarb, dichlofenthion, isamidofos, fosthietan, isazofos ethoprophos, cadusafos, terbufos, chlorpyrifos, dichlofenthion, heterophos, isamidofos, mecarphon, phorate, thionazin, triazophos, diamidafos, fosthietan, phosphamidon, imicyafos, captan, thiophanate- methyl and thiabendazole.

Nematicidally active biological agents include any biological agent that has nematicidal activity and could be used with the present invention. The biological agent can be any type known in the art including bacteria and fungi.

The wording “nematicidally active” refers to having an effect on, such as reduction in damage caused by, agricultural-related nematodes. Examples of nematicidally active biological agents include Bacillus firmus, B. cereus, B. subtilis, Pasteuria penetrans, P. nishizawae, P. ramosa, P. thornei, and P. usgae. A suitable Bacillus firmus strain is strain CNCM 1-1582 which is commercially available as BioNem™ A suitable Bacillus cereus strain is strain CNCM 1-1562. Of both Bacillus strains more details can be found in US6,406,690.

Examples of primers and safeners include benoxacor, cloquintocet-mexyl, cyometrinil, fenclorim, fluxofenim, oxabetrinil and daimuron.

As noted above the agrochemicals of the invention may be provided in the form of formulated products. There can be many purposes for doing so, and for each a different component might be added. For example, it might be desired to protect rice seed during storage and transport from any toxicity issues associated with close physical proximity to an agrochemical. Many other purposes and solutions will be apparent to the skilled person.

Other additives which are used with seeds may advantageously be provided in conjunction with the present invention. Such additives include, but are not limited to, uv- protectants, colorants, brighteners, pigments, dyes, extenders, dispersing agents, excipients, anti-freeze agents, herbicidal safeners, seed safeners, seed conditioners, micronutrients, fertilizers, surfactants, sequestering agents, plasticizers, polymers, emulsifiers, flow agents, coalescing agents, defoaming agents, humectants, thickeners, and waxes. Such additives are commercially available and known in the art.

Coated rice seeds according to the present invention are more particularly used for direct sowing, especially in flooded field.

Direct sown rice can be planted into a flooded field or a field without excess water. In flooded fields, the soil is covered with a layer of water typically from 3-10 cm deep before or after sowing. Rice is either sown onto the soil surface or drilled into the upper layer of the soil. Whether rice seeds are sown upon the surface or drilled into the soil, either way the seed is submerged in water. Such a planting method is referred to as direct sown rice in flooded field, which is the preferred focus of the present invention.

Another object of the present invention is a process for preparing coated rice seeds, more particularly coated rice seeds as described in the present invention, said process comprising the following steps: placing rice seeds, optionally coated by a first coating of a treatment composition and/or by a second coating of an agrochemical composition, in a treatment vessel; optionally in the treatment vessel, wetting the rice seeds, more preferably in adding water on rice seeds, under stirring; adding in the treatment vessel, silica particles; mixing the content of the treatment vessel until to obtain a coating of the silica particles onto the rice seeds, and more preferably to obtain a homogenous coating of the silica particles onto the rice seeds; and optionally drying the coated rice seeds.

The treatment vessel can be any appropriate mixing vessel or container well-known in the art, and can be for example a pan granulator or rotational-type mixer (such as that used in building trades to mix concrete).

The optional wetting step can help to improve the adherence of the silica particles onto the rice seeds. Water is generally used to increase the adherence of the rice seeds, and can come from the addition of water as such or from a liquid composition having a water content.

The optional drying step may be at any suitable temperature and humidity. It is believed drying at room temperature or slightly heated temperature (e.g. 35°C) for about 1 minute to 1 day may provide good results with a minimum of energy inputs. It is possible also to dry seed at room temperature for more than 1 day reducing moisture of seed slowly such as 7days-14 days. A fluidized dryer can be used for the drying step.

Another object of the present invention is a method of improving the floating tolerance of rice seeds, comprising the following steps: treating rice seeds with silica particles as described in the present invention; optionally, preparing the field for sowing, especially in mixing the soil and flooding water in the field; sowing the treated rice seeds; optionally, after sowing the treated rice seeds, flooding water in the field; and growing the rice crop.

The following non-limiting examples demonstrate the improved behaviour associated with coated rice seeds according to the present invention.

The silica particles used to prepare the external coating in the following examples are detailed below:

Silica particles applied as solid form are the silica particles Carplex 80, commercialized by Evonic;

Silica particles applied as liquid form are the silica particles Carplex 80 commercialized by Evonic, which are mixed with water to obtain a concentration of 15% by weight of silica particles over the total volume of the liquid composition.

The objective of these examples was to evaluate the activity of float tolerance of silica particles.

As a base of treatment, rice seeds were coated with a first coating of a treatment composition to form coated rice seeds “CRS1”. Said treatment composition is the composition commercially available under the name OXOs DS from Syngenta, and 0.5 kg of OXOs DS is applied per 1 kg of rice seeds (i.e. non-coated rice seeds).

Then, the indicated amount of Silica particles in Table 1 is directly applied onto said first coating to form an external coating around CRS1 and to obtain coated rice seeds “CRS2”.

The coated rice seeds “CRS1” are obtained as follows: placing rice seeds in a treatment vessel and wetting the rice seeds in adding water in the treatment vessel, under stirring; adding the treatment composition in the treatment vessel; and drying the rice seeds coated with the first coating of a treatment composition in using a fluidized bed dryer, to form coated rice seeds “CRST’. The coated rice seeds “CRS2” are obtained as follows: wetting the coated rice seeds “CRS1” in adding water in the treatment vessel, under stirring; adding silica particles in the treatment vessel; mixing the content of the treatment vessel until to obtain a coating of the silica particles onto the rice seeds; and drying the “CRS1” rice seeds coated with the external coating of silica particles in using a fluidized bed dryer, to obtain coated rice seeds “CRS2”.

Based on the application form and the application rate gathered in Table 1, the hydrophilicity, the water spreading speed as well as the float tolerance were determined.

In Table 1, the application rate of the external coating is expressed per kg of seeds, or in other words per 1.5 kg of seeds surrounded by the first coating of the treatment composition.

The hydrophilicity is the speed of water absorption which was evaluated as follows: 10 pl of water drop was placed onto the coated rice seeds (10 coated rice seeds), then soaking speed of drop was visually observed.

For example, the coated rice seed (CRS1) with only the first coating of the treatment composition is hydrophobic, and water drop was not soaked within 30 seconds, and thus was evaluated as level 0. When water drop is soaked onto CRS2 for 3 seconds, it was evaluated as level 3.

Water spreading speed on seed surface is influenced by water repellency. For example, a low water repellency of seed surface provides quick water spreading on seed surface. Water spreading speed was evaluated as follows: 10 pl of water drop was placed on stainless steel tray, then the coated rice seeds (10 coated rice seeds) were placed on said water drop. Ascending speed of water from bottom to upside was visually observed in the level of 0-3.

For example, for the coated rice seed (CRS 1) with only the first coating of the treatment, water drop was not transferred from bottom to upside within 30 seconds, and thus was evaluated as level 0. When water drop is transferred to upside of the coated rice seed CRS2 along coating surface for 3 seconds, it was evaluated as level 3.

The float tolerance was evaluated as follows: 10 of CRS1 and CRS2 were placed on stainless steel bad then water is irrigated by pump. Level of movement from the placed point of the coated rice seeds by water flow was evaluated by level as A: no movement, B: slight movement, C: moved far from the point.

Table 1

The results obtained in Table 1 present a significant improvement in float tolerance while guaranteeing a good hydrophilicity, thanks to Ex. 2, 3 and 4. More particularly, when the external coating is obtained by applying silica particles in solid form (Ex. 2 and 3), the float tolerance is even better than with an application in liquid form (Ex. 4).