WO2001080646A1

WO2001080646A1 - Inorganic nematocides

Info

Publication number: WO2001080646A1
Application number: PCT/IT2001/000169
Authority: WO
Inventors: Pietro Zanuccoli
Original assignee: Zanuccoli, Giuseppe, Antonio
Priority date: 2000-04-20
Filing date: 2001-04-02
Publication date: 2001-11-01
Also published as: ITCT20000009A1; AU2001252537A1

Abstract

The present invention relates to inorganic bio-oxidable product consisting of elemental sulphur, and/or some inorganic compounds and/or some inorganic acids and characterized in that it is introduced into the soil in solid, liquid or gaseous form or solution of the irrigation water in amounts sufficient to cope and/or control and/or eliminate the nematodes (or roundworms) of the soil, particularly root-gall nematodes.

Description

INORGANIC NEMATOCIDES

The present invention relates to an inorganic bio-oxidable product and/or its inorganic compounds and/or inorganic acids.

The invention further relates to methods of using the above said product to cope nematodes or roundworms. As known, nematodes, or roundworms, have the body covered with a moult subject proteinaceous cuticle, chemically constituted of complex amino acid chains, easily etched by aqueous solutions of inorganic acids at pH values lower than 5 - 5,5, specially when the moult is occurring. Furthermore it is known that nematodes currently are coped by various means among which methyl bromide, poisonous for both humans and environment, considered, inter alia, as depleting agent for the ozone layer, being a very heavy and water immiscible gas.

In addition synthetic molecules, resulting in remarkable effects on nematodes yet resolving, not always, only the problem of nematodes without generating positive side effects, are used. Furthermore also these products can be dangerous for humans.

Accordingly it is suggested, according to the present invention, a product based on sulphur, and/or its some compounds and inorganic acids, to cope and/or control, in some cases, and/or eliminate, in other cases, the soil nematodes, particularly those called root-gall nematodes.

According to recent studies carried out by the Applicant the best products therefor, with an immediate response for such use, are sulphuric, nitric, orthophosphoric and other phosphoric, and hydrochloric acids. As known, sulphur and/or its compounds, as polysulphides and thiosulphates, in order to be converted in sulphuric acid, firstly must be bio-oxidised by thiobacilli and other sulphur metabolising micro-organisms. Usually the bio-reactions involving micro-organisms are slow and not suitable to produce sulphuric acid in such large amounts to obtain the pH required to cope and/or control and/or eliminate the nematodes.

An object of the present invention is to provide remedies allowing to accelerate the oxidation to sulphuric acid of elemental sulphur and compounds thereof as polysulphides and thiosulphates. According to the invention, the amount of sulphur or compounds thereof, to be converted in sulphuric acid, must be as more remarkable as more basic is the pH of the soil (and therefore higher the content of free hydrogen carbonates, carbonates, calcium, magnesium, sodium, etc.). In fact it is required the amount of acid in the soil to be enough to react also with the proteinaceous cuticle forming the "skin" of the nematodes, constituted of complex amino acids.

By means of the remedy suggested according to the present invention, in order to obtain the same objective and results it is sufficient to control the amount of the above listed inorganic acids introduced into the soil.

It is therefore an object of the present invention an inorganic product characterised in that it consists of elemental sulphur, and/or some its inorganic compounds and/or some inorganic acids and characterised in that it is introduced into the soil in solid, liquid or gaseous form or solution of the irrigation water in amounts sufficient to cope and/or control and/or eliminate the nematodes (or roundworms) in the soil, particularly root-gall nematodes. Preferably, according to the invention, said inorganic product can be based on sulphuric acid, nitric acid, phosphoric acids, hydrochloric acid, sulphurous acid.

Again according to the invention said product can be used at concentrations different from 100 %. Furthermore, according to the invention, said product can be based on sulphur trioxide, sulphur dioxide.

In addition, according to the invention, the product can be also constituted of one or more of above products used as mixtures thereof. Furthermore, according to the invention, said product can be based on powdered micronized sulphur having particle size such to result in 5 % maximum residues from both 5 and 500 micron hole sieves.

Moreover according to the invention, the contemporary pasteurisation of the soil and acceleration of the bio-oxidation can be used by the solarization method.

Further, according to the invention, said product can be based on colloidal elemental sulphur, i.e. with a diameter below 10^"3 mm, or fuming sulphuric acid, known also as oleum, or polysulphides of alkaline, alkaline earth metals or ammonium.

In addition, according to the invention, said product can be introduced under the soil by means of injection piles or irrigation water.

Again according to the invention said product can be based on ammonium or potassium thiosulphate.

Below various methods of using the products according to the invention will be described. First method

Use of sulphuric acid such as it is and/or other inorganic acids as nitric, phosphoric, hydrochloric acids, much or less diluted, by the introduction thereof into the irrigation water.

The amount of H₂SO4, to be introduced into the soil, as a background treatment must be such that the resulting pH of the soil environment is < 5-5,5, around which value the cuticles constituting the proteinaceous skin of the roundworms begin to decompose. The amount varies also depending on the characteristics of the soil, namely: pH, specific texture of the soil, presence and amounts of carbonates, hydrogen carbonates, chlorides, Na, Ca, Mg, free or bonded, etc.

To obtain the objective, from fifty to ten thousands kg/hectare of pure, fuming or diluted sulphuric acid (the latter two in amounts proportional to pure or commercially pure product) can be required, paying attention, anyway, to avoid the pollution thereof from agronomically undesirable elements as heavy metals, with higher or lower quantitative peaks, again dependent on pH, soil type, salinity, texture, etc.

In order to maintain the content of SO_T in the soil water at an optimum level, i.e. suitable to result in the not survival or departure of the nematodes, these methods are to be repeated or coupled with those below indicated.

It is to be pointed out to avoid the addition of fertilizers abundantly because the high content of sulphuric acid maintains the nutrients soluble in the soil water and makes the same suitable to be adsorbed by the plant roots, resulting therefore in potential phytotoxic and/or antagonistic effects which can be present among various exceeding nutrients, as is well known by those skilled in the art. Furthermore H2SO4 permits in basic soils the use of fertilizers like phosphorites and potassium chloride, in the presence of or without brackish irrigation waters, because it reacts with the first generating as reaction product soluble phosphoric acid and reacts also with the others, i.e. KCI and brackish waters, removing both chlorine, as chloride ions dissolved in the excess irrigation water, and sodium, as sodium sulphate, both highly water soluble.

The use, as background initial treatment, of more or less strong acids, as nitric or phosphoric, in the place of sulphuric acid, has been discarded because of the possible nutritional unbalances, especially as to seasonal crops.

The excess of nitrogen or phosphorus, ready available to be assimilated, results in severe drawbacks for the normal growth of seedlings which will sprout or being in a growing stage. In this case nitric and/or phosphoric in mixture with sulphuric acid can be used, paying attention to the nutritional aspects.

On the contrary the use of acids different than sulphuric is possible when the plant is adult or perennial. The feed of phosphorus and nitrogen derived from acids is required for the normal crop growth, always paying attention to not exceed in nutrients in the attempt to have in the soil high levels of anions of strong acids.

Hydrochloric acid can be highly phytotoxic and it is usable in the presence of high levels of calcium and irrigation water aiding the removal of chlorine in the irrigation water in the form of calcium chloride.

The advantage obtained by this method consists in that the results are obtained quickly and it is suitable for any crop, protected or not.

It is possible to reiterate the treatment of the growing crop, using amounts as required, taking advantage also of the nutritional effect of the other acids.

Said method can be used in any climate and at any ambient temperature suitable to more usual crops, it increases the infiltration of the water, frees almost all of the macro-, meso- and micro-elements blocked in the soil, making the same available for the plant nutrition. The drawback derives, apart from those before indicated, from the handling of strong acids which can be harmful for the user.

Second Method Use of powdered micronized sulphur having particle size such to result in 5 % maximum residues from both 5 and 500 micron hole sieves with the contemporary pasteurisation of the soil by the solarization method It is to be pointed out that sulphur is commercially available as powder; or, in order to avoid discomforts from the cloud of the powder causing undesirable effects, in the form of a wettable powder (to be wetted before the spreading), granule, dispersible microgranule, dispersible pellet, dispersible lentil, rotoform, lenticular, all as water dispersible and/or disintegrable forms; or, furthermore, in the form of cream, slurry, wetted precipitate, residue of chemical reaction, wet sulphur blasting from petroleum or petroleum extractive industry, etc.

Moreover it is to be explained what is consisted of the solarization method and the reason of the use thereof. Solarization is a biological method of disinfecting and disinfesting the soil from naturally occurring animal micro- and macro- parasites, seeds of pests. It consists of the soil exposure to the sun rays in the presence of an over-saturated field capacity such that the temperature of the water used to "pasteurise" the soil is about 55°C over a period of at least 7 weeks.

In order to obtain the best results within the prefixed periods of time it is required that this methods is applied during the warmest period of the year when the irradiation energy of the sun, i.e. the heat energy in kW/m² transferred from the sun to the soil by radiant heating, is maximum. To avoid the dispersion of the sun heat, on the contrary to accumulate the same, it is required to take advantage from the "greenhouse effect" by covering with a sheet of optical plastic.

Being required to operate in the presence of an over- saturated field capacity, water is added, possibly pre-heated by the same sun rays, to maintain the temperature under the plastic sheet as close as possible to the maximum value reached during the treatment.

In the southern Sicily, for example, the best operation period is from the last decade of June and the second decade of August.

To obtain expected results it is necessary to operate as below indicated.

Elemental sulphur, powdered or in other above indicated forms or not, is applied before the covering of the soil with the plastic sheet. By means of agricultural tools conventionally used in these cases, variable amounts of sulphur, from less than 0,05 Kg/m² to 0,25 Kg/m² and above, are mixed with the surface soil to a maximum depth of 5-6 cm.

The amount/m² will be lower for powdered sulphur or derived from granule wet disintegration or in wet condition, 95 % passing through a 5 micron hole sieve. The amount/m² will be higher for powdered sulphur obtained by methods above reported 95 % passing through a 500 micron hole sieve.

These amounts will be dependent also on the soil salinity, typology, texture, pH, etc.

As known, some bacteria, mostly belonging to the family of thiobacilli, in the presence of water and oxygen, convert sulphur in sulphuric acid. Higher the temperature higher the conversion rate.

When in a soil 500 ppm of elemental sulphur with a particle size from 250 to 180 micron are applied, after a 30 day incubation, the following ppm of elemental sulphur are converted in sulphuric acid at the specified temperatures: less than 2 ppm at 4°C, less than 4 ppm at 10°C, less than 8 ppm at 23°C, about 20 ppm at 30°C, about 42 ppm at 40°C.

After a 60 day incubation these values are essentially the same for the temperatures of 4° and 10°C, whereas the total converted amounts are about 13 ppm at 23°c, about 58 ppm at 30°C, about 72 ppm at 40°C.

At higher finesses the per cent of sulphur converted in sulphuric acid is much higher depending on the attacking surface available for the thiobacilli.

It is easy to remember that the total surface area of a 1 cm side cube, whose hypothetical weight is one gram, is 6 cm².

Whereas if the sides of said cube are divided by ten parts 1000 little cubes with 0,1 cm sides are obtained, whose total weight and surface area amount to 1 gram and 60 cm², respectively.

If again the sides of these little cubes are divided by ten, for each thereof 1000 little cubes with 0,01 cm sides are obtained, thus leading the total number of the little cubes obtained from the first cube weighing 1 gram to 1000000 (one million) and the total surface area to 600 cm² and so on. To explain the mechanism being triggered a human scale example is reported, with reference to the micro-organism scale.

Imagine to be at a wedding reception wherein the guests can eat the wedding cake using just a dessert spoon for each of them by approaching the cake laying majestically as a whole on the table in the middle of salon.

As a consequence only few guests at the same time can take and eat some wedding cake. Successively they leave the place to other guests which in turn will eat and then analogously substituted by others.

So on several ten minutes, rather hours, will be necessary till all eat the wedding cake.

If, on the contrary, the same guests have, in addition to the dessert spoon, a saucer for each containing a slice of the wedding cake such that the total amount is the whole, it will take only few minutes till the slice and therefore whole wedding cake are consumed completely.

The more the guests present the smaller slices and the less time will be necessary to consume the same.

Within the microscopic environment of the bacteria the situation and the results are identical: the thiobacilli eat more sulphur and therefore the smaller particles of elemental sulphur to be attacked the less time will be necessary to produce the same amount of sulphuric acid.

In 1 cm side cube of known weight there will be X bacteria at the same time eating from a 6 cm² surface; whereas in one million of 0,01 cm side little cubes totally amounting to the same weight there will be X times 600 cm² (total surface of smaller cubes) divided by 6 cm² (surface of the whole cube) bacteria, i.e. X times 100 bacteria. That is 100 times over bacteria can feed themselves on sulphur, oxidising it to sulphuric acid. As before said the higher ambient temperature the more voracious bacteria ant that factor 100 can be multiplied again by some ten times.

All this is reported to explain in which way elemental sulphur is to be . used in order to obtain the generation of sulphuric acid in the soil, biologically, firstly, and in such amounts, after, to make the soil unsuitable to the survival of the nematodes by the induced acidity. The application of sulphur in amounts as those described, when applied over several years, provided the total elimination of the nematodes,. Third Method Incorporation of colloidal sulphur, i.e. with finesses below 10^~3 m^"3, in wet and oxygenated soil Again according to the principle that the smaller sulphur particles the higher the oxidation rate, in the soil, for a maximum depth of 5-6 cm, as background treatment, amounts of colloidal sulphur from 0,03 to 0,09 Kg/m² and over, depending on soil typology, pH and so on, are to be incorporated. As required higher or also smaller amounts can be used.

Just because colloidal sulphur is particularly suitable to be attacked by the thiobacilli it is not rigorously necessary during the summer to use the solarization to accelerate the oxidation of the soil, in specified thermal conditions of the latterl. When required the introduction of the sulphur into the soil during the seasonal cultivation or vegetative cycle is repeated. Colloidal sulphur, spread by irrigation, can be used as maintenance product in addition to the use thereof for the treatment indicated in the present and before explained First and Second Methods.

Fourth method Incorporation into the soil of polysulphides of alkaline (Na, K) and alkaline earth metals (Ca, Ba) and ammonium.

In polysulphides the term n in S_n ^2" can have values from 2 to 9, usually the most stable having 4 atoms of S.

In this case it is also possible to contribute to the plant nutrition by means of a treatment with polysulphides of calcium and potassium, which release both metals, in addition to the sulphur, without particular problems for the plants.

These products are introduced into the soil alone or in admixture when in solid state or by irrigation when it is possible to prepare aqueous solutions or suspensions thereof. It is waited for their decomposition by the soil reaction or better still, to have a more rapid decomposition, an irrigation with a solution of sulphuric, nitric or hydrochloric acids is carried out. The acid will react with the polysulphides resulting in elemental sulphur, hydrogen sulphide and salt of alkaline or alkaline earth metal, as used. The closer to the stoichiometry the ratio of the amounts of sulphuric acid and alkaline or alkaline earth metals the higher the decomposition rate because the production of elemental sulphur trigger the biological production of further sulphuric acid which will react with the polysulphide producing elemental sulphur, sulphuric acid and sulphate of the alkaline metal and so on. Hydrogen sulphide in turn will be oxidised to sulphuric acid in the presence of water and oxygen.

Due to their instability in the presence of air and/or humidity contained therein some alkaline or alkaline earth polysulphides currently are not available.

The amounts to be used before the beginning of the seasonal cultivation and when the soil temperature is higher than 15-16°C vary from 0,04 to 0,12 Kg/m². It is to be waited till, by digging over soil, the smell of rotten eggs, typical of the presence of hydrogen sulphide, disappears, to avoid phytotoxic phenomena, especially when seedlings to be planted out are involved. Ammonium polysulphide at ambient temperature is a brown- red, black liquid and because easily decomposed in air while perfectly compatible with bases it is stored in pressure cylinders under ammonia atmosphere. It can be spread as such it is in the soil by injections or added to the irrigation water wherein it is immediately decomposed resulting in elemental sulphur and ammonia.

Its use is more appropriate when, in addition to the acidification, it is required to provide nitrogen to the soil.

Fifth Method Irrigate with water containing SO? or SO,, as background irrigation and continue, successively; at lower concentrations

SO₂ is added to the irrigation water paying attention to maintain all in solution in order to avoid the air dispersion generating damage to people. pH will reach enough low values to not allow the survival of nematodes in the soil. It is to be pointed out that sulphur dioxide is one of the agents causing acid rain which have pH of 3 just due to the part thereof dispersed in the atmosphere. SO₂ will then converted in SO3 reacting at last with water and successively like sulphuric acid.

The amounts to be spread by one or more treatments will be from 32 to 640 Kg/hectare, paying attention to maintain all in solution during the spreading. An indicative value, not to be exceeded and to be checked in the field, to avoid damages to humans, plants and things is 1% maximum at a water temperature of 30°C. The pH value of the soil, like in the other cases, must be such to not allow the survival of the nematodes therein. This amount can be much higher or lower depending on the characteristics of the soil, pH, structure, texture, presence of hydrogen carbonates, carbonates, sodium clays and so on.

As to anhydrous SO3 it is to be pointed out that upon the introduction thereof into the water it is converted in sulphuric acid with a successive behaviour as described in the First Method. The amount to be used is from 40 to 800 Kg/hectare.

The amount per hectare can be much higher depending on the presence of sodium, calcium, hydrogen carbonates, carbonates, etc.

Sixth Method Introduction of ammonium thiosulphate or potassium thiosulphate into the soil

Ammonium thiosulphate, colourless and odourless liquid, has higher acidifying capacity than potassium thiosulphate because its decomposition in the soil generating firstly elemental sulphur and ammonium sulphate, then the latter is decomposed in sulphate ion and ammonia which is oxidised to nitric ion acidifying in turn the water of the soil.

Little more than 148 Kg of pure ammonium thiosulphate, after its introduction into the soil, will produce at the end of the biological reactions 192 Kg of SO₄ ^~ and 92 Kg of NO3^— ions, respectively. The introduction of ammonium thiosulphate into the soil is interesting as a background treatment against the nematodes when in the there is a chronic nitrogen deficiency. It is to be paid attention to be not in excess of nitrogen because the same as nutrient tends to result in a rapid growing of the seasonal plants with very soft and weak tissues, many leaves and very poor "skeleton". To accelerate its decomposition in the soil, strong acids, also during the final step of irrigation, can be used, being decomposed by the same.

On the contrary 190 Kg of potassium thiosulphate after its introduction into the soil will produce 96 Kg of SO₄ ^""sulphate ions while potassium sulphate, after dissociation in anions and cations, will be active very marginally to the acidification of the soil, except when used, at comparable conditions of the soil, in amounts three times higher than ammonium thiosulfate.

To obtain the objective of controlling the nematodes a combination of the various above reported methods can be used, in succeeding steps or, when it is possible, in combination among them, using that'which, case by case, depending on the specific type of the soil and crop, gives the best results.

To avoid undesired water pollution to the soil wherein there is a lack of calcium, magnesium ions, etc. both bound and free, can be added powdered calcium carbonate, dolomite, etc., which will buffer the acids generated in excess. Such an effect is very similar to that obtained naturally in the soils with basic pH and anyway the addition is useful as meso/micro-nutrients in those soils lacking in the same. The present invention is described with reference to some preferred embodiments thereof but it is to be understood that variations and/or modifications will be carried out by those skilled in the art without departing from its scope.

Claims

I. Inorganic product characterised in that it consists of elemental sulphur, and/or some its inorganic compounds and/or some inorganic acids and characterised in that it is introduced into the soil in solid, liquid or gaseous form or solution of the irrigation water in amounts sufficient to cope and/or control and/or eliminate the nematodes (or roundworms) of the soil, particularly root-gall nematodes.

2. Product according to claim 1 characterised in that it is based on sulphuric acid.

3. Product according to claim 1 characterised in that it is based on nitric acid.

4. Product according to claim 1 characterised in that it is based on phosphoric acids.

5. Product according to claim 1 characterised in that it is based on hydrochloric acid.

6. Product according to claim 1 characterised in that it is based on sulphurous acid.

7. Product according to anyone of claims 2, 3, 4, 5, or 6, characterised in that it can be used at concentrations different from 100 %.

8. Product according to claim 1 characterised in that it is based on sulphur trioxide.

9. Product according to claim 1 characterised in that it is based on sulphur dioxide.

10. Product according to anyone of claims 2, 3, 4, 5, 6, 7, 8 or 9 characterised in that one or more of these products are used as mixtures thereof.

II. Product according to claim 1 characterised in that it is based on powdered micronized sulphur having particle size such to result in 5 % maximum residues from both 5 and 500 micron hole sieves.

12. Product according to claim 11 characterised in that it is contemplated the contemporary pasteurisation of the soil and acceleration of the bio-oxidation by the solarization method.

13. Product according to claim 1 characterised in that it is based on colloidal elemental sulphur, i.e. with a diameter below 10^"3 mm.

14. Product according to claim 13 characterised in that it is contemplated the contemporary pasteurisation of the soil and acceleration of the bio-oxidation by the solarization method.

15. Product according to claim 1 characterised in that it is based on fuming sulphuric acid, known also as oleum.

16. Product according to claim 1 characterised in that it is based on polysulphides of alkaline and alkaline earth metals.

17. Product according to claim 16 characterised in that it is contemplated the use of any of the products according to claims 2, 3, 4, 5,

6, 7, 8, 9, 10, 15 to accelerate the decomposition reaction.

18. Product according to claim 1 characterised in that it is based on ammonium polysulphide.

19. Product according to claim 18 characterised in that it is introduced under the soil by means of injection piles.

20. Product according to claim 18 characterised in that it is introduced into the soil by means of the irrigation water.

21. Product according to claim 18 characterised in that any of the products according to claims 2, 3, 4, 5, 6, 7, 8, 9, 10, 15 is used to accelerate the decomposition reaction.

22. Product according to claim 1 characterised in that it is based on ammonium thiosulphate.

23. Product according to claim 22 characterised in that any of the products according to claims 2, 3, 4, 5, 6, 7, 8, 9, 10, 15 is used to accelerate the decomposition reaction.

24. Product according to claim 1 characterised in that it is based on potassium thiosulphate.

25. Product according to claim 24 characterised in that any of the products according to claims 2, 3, 4, 5, 6, 7, 8, 9, 10, 15 is used to accelerate the decomposition.

26. Product according to claim 1 characterised in that it is based on a mixture of the products according to claims 11 and 13.

27. Product according to claim 1 characterised in that it is based on two or more than two of the products according to one or more of claims 11 , 15, 18, 21 , 24.

28. Product according to anyone of the preceding claims characterised in that to accelerate the decomposition and biological oxidation reactions the method of soil solarization is used.