METHOD FOR SUPPLYING MICRONUTRIENT METALS TO PLANTS

Abstract: A method for supplying a micronutrient metal element to a plant comprising administering to the plant a micronutrient composition containing cations (A) which are selected from Mn ions or Fe ions or mixtures thereof as well as anions which are formate ions and optionally ions of a C2-5 alkanoic acid or a mixture of such acids, the composition optionally further containing cations (B) selected from Cu ions and Zn ions as well as mixtures of such ions, and optionally further containing ammonia.

Description: METHOD FOR SUPPLYING MICRONUTRIENT METALS TO PLANTS FI ELD OF THE I NVENTION The present invention relates to a method for supplying micronutrient metal elements to plants as well as aqueous micronutrient metal element compositions for use in the method . BACKGROUND OF THE I NVENTION I n order to grow, all plants need small amounts of a number of ele¬ ments, e.g . boron , cobalt, copper, iron , manganese, molybdenum, and zinc. These minerals are called trace elements or micronutrients because they are essential to the life processes of plants, but are only present in the plant tissues in extremely small concentrations; only a few tens or hundreds of part per million . However, their importance is disproportional to the concentration in which they are present since they act as catalysts in such essential life processes as photosynthesis and hydrolysis . Only small amounts need to be supplied to the plants , but without these small amounts growth will stop . Deficiency of one or more trace elements may be caused by at least two factors : firstly, the soil in which the plants grow is itself defici- ent of the trace element, and secondly, the availability of the trace element to the plants, due to e. g . soil chemistry, is reduced . Thus, sandy soil or soil with a high content of humus may lead to deficiency in manganese. Trace metals should normally be presented to the plants in a certain oxidation state which may not necessarily be the most stable form of that element under the conditions in question . Thus, manganese should be available to plants as Mn ( l l ) , but this form of manganese may often be oxidized into MnO 2 - Li kewise, iron should be available as Fe( l l ) but this form is easily oxidized to Fe( l l l ) which , due to its Lewis acid activity, has a tendency to "burn" the leaves of sprayed plants . DESCRI PTION OF THE PRIOR ART Trace elements have been supplied to plants in the form of simple salts such as MnSO 4 but it has usually been necessary to supply it in rather high concentrations such as concentrations corresponding to 5 800-1200 g Mn/ha . Manganese sulfate is usually supplied to the farmer as a dry powder for solution in water. There is, however, a risk of dusting and breathing of the somewhat toxic manganese sulfate. Furthermore, certain plants such as citrus trees are sensitive to high concentrations of sulfate ions . The use of concentrated solutions of 0 manganese sulfate is, however, apparently not practicable since it appears that such stock solutions have a limited shelf life due to the formation of MnO~ . I n recent years, a number of products incorporating chelated trace elements have been commercially available. A commonly used chelating 5 agent is EDTA (ethylene diamine tetra acetic acid) which is able to on the one hand prevent deterioration of stock solutions and on the other hand to ensure availability of the trace elements to the planβ, even if the chelated compounds arό sprayed onto the soil . The chelated compounds are, however, sufficiently expensive for economy to become 0 a factor of importance. SUMMARY OF THE I NVENTION The present invention obviates or substantially reduces the above discussed disadvantages of the previously used types of trace element compositions . 5 The invention relates to a method for supplying a micronutrient metal element to a plant comprising administering to the plant a micronutrient composition containing cations (A) which are selected from Mn ions or Fe ions or mixtures thereof as well as anions which are formate ions and optionally ions of a C«_ c alkanoic acid or a mixtu re of such 0 acids . Since formic acid, unlike the higher fatty acids, can be oxidized to carbonic acid, formic acid provides an antioxidant protection of Mn and Fe to keep these ions predominantly at a suitable oxidation level. DETAILED DESCRIPTION OF THE INVENTION For reasons of ease of application, it is preferred that the micro¬ nutrient composition is in the form of an aqueous solution of the salt in question. In a preferred embodiment, the composition used in the method may further contain cations (B) selected from Cu ions and Zn ions and mixtures of such ions. As examples of C~_ ,. alkanoic acids may be mentioned acetic acid, propionic acid, butyric acid, isobutyric acid, and valeric acid. Among these acids, acetic acid is preferred since acetic acid appears to be able to form complexes with i.a. Mn and Cu. As examples of specific salts comprising the above-described cations and anions may be mentioned: Manganese( 11) formate ManganeseC II) acetate Manganese( II) propionate Manganese( II) butyrate Manganese( II) isobutyrate Manganese( II) valerate Manganese( III) formate Manganese( III) acetate ManganeseC III) propionate Manganese( III) butyrate Manganese( III) isobutyrate ManganeseC III) valerate IronCI I) formate Iron (I I) acetate I ron ( I I) propionate IronCI I) butyrate I ron (I I) isobutyrate IronCI I) valerate I ron ( I II) formate I ron (I 11 ) acetate IronCI II) propionate IronCI II) butyrate IronCI II) isobutyrate I ron C I II) valerate Coppe r(ll) formate Coppe rCII acetate Coppe r(ll) propionate Coppe rCII) butyrate Coppe rCII) isobutyrate Coppe r(l I) valerate Zinc f ormate Zinc a cetate Zinc p ropionate Zinc b utyrate Zinc i sobutyrate Zinc v alerate It is preferred that the molar ration between the formate ions and the ions of the C ^ e alkanoic acid is in the range from 1:1000 to 1:0 C"1:0" indicating the presence of only formate ions); in particular from 1:1000 to 1:40 in the case of Mn ions, and from 1:10 to 1:0 in the case of Fe ions. In the method of the invention and for the treatment of manganese deficiency, a preferred cation (A) is Mn, in particular the MnCH) ion, i.e. that a preferred micronutrient metal element salt is manga- nese(ll) formate (Mn (HCOO)-). I n a preferred embodiment of the method of the invention , the com¬ position further contains NH 3 (ammonia) since ammonia forms complexes with a number of metal ions, i . a . Cu, thereby fu rther stabilizing the composition . I n particular, the concentration of ammonia may be up to 4 molar equivalents per molar equivalent of the cations (A) and op¬ tionally (B) or even higher in order to ensure a suitable equilibrium constant for tetraamine complexes . Salts of the above described kind used in the method of the invention exhibit a suitable solubility in water while at the same time providing good availability to plants upon application and exhibiting good long- term stability in aqueous solutions . I n the method of the invention , the amount of micronutrient composition administered to the plants will , of course, depend on such factors as presence of the particular micronutrient metal element in the soil, other soil chemistry factors such as pH, the type and variety of the plants, climatic factors (rainfall ect. ) as well as a host of other factors . I n the case of administration of manganese, however, amounts corresponding to 25-400 g manganese per hectare will be sufficient for a wide variety of crops, preferably 50-300 g Mn/ha, in particular 100-200 g Mn/ha such as 160 g Mn/ha . With respect to Fe and Zn , these ions may be used in application amounts corresponding to those indicated above for Mn . Cu may be applied in amounts of 8-130 g Cu/ha, preferably 16-100 g Cu/ha, in particular 30-70 g Cu/ha such as about 55 g Cu/ha . These ranges are not in any way limiting, and a person skilled in the art may through conventional methods be able to establish in each individual case the amount of micronutrient metal element salt to be used in the method of the invention . For leaf spraying, the concentration of manganese in the spraying solution ready for use is typically 0.001 -1 .0% Mn, such as 0.04% Mn . Examples of plants to which the micronutrient metal element salts may be administered in the method according to the invention are mono- and dicotyledonous plants such as sugar beet, rapeseed, wheat, rye, barley, oats, maize, millet, grapes, citrus trees, apple, pear, apricot, cherry, plum, peach, rose, and grass. These examples are, naturally, not limiting since the method of the invention may be applied to any plant suffering from deficiency of micronutrient metal elements . In the method of the invention the micronutrient metal element salt may be administered in any of the ways commonly used for the appli- cation of micronutrients such as leaf spraying, soil spraying or soil injection, leaf spraying being preferred . I n the case of soil spraying or soil injection, the micronutrient metal concentration may be up to ten times the concentration used in leaf spraying . Furthermore, the method of the invention may be used in combination with or simultaneously with other chemical plant treatments . Thus, the micronutrient metal element salt may be administered in combination with other agricultural chemicals such as herbicides, pesticides or growth promoters . The composition for use in such a treatment may be prepared by simply mixing the diluted micronutrient metal element salt composition used in the method of the invention and the diluted herbicidal, pesticidal or growth promoting composition . Such mixed compositions may be in any of the forms commonly used for herbicides, • pesticides and growth promoters, in particular those forms based on aqueous solutions, emulsions or suspensions . The micronutrient metal element salts used in the method of the invention may be prepared by reacting a salt of the metal element with formic acid and optionally the appropriate C~__. al kanoic acid . The reaction may preferably be carried out in an aqueous solution and at a temperatu re between room temperatu re and the boiling point of the mixture. The metal element salt is preferably of a type which, upon reaction with the acid, does not generate salt by-products . Examples of such metal element salts are carbonates (where the anion escapes as carbon dioxide) , oxides, and hydroxides such as man- ganeseCI I ) carbonate, manganese( l l ) oxide, iron (I I ) carbonate, iron C I I I ) carbonate, or iron C H ) hydroxide. The invention further concerns an aqueous micronutrient metal element salt composition in which the cations (A) are selected from Mn ions or Fe ions or mixtures thereof, and the anions are formate ions and optionally ions of a C~_ 5 alkanoic acid or a mixture of such acids . I n a preferred embodiment, the composition fu rther contains cations CB) which are selected from Cu ions and Zn ions and mixtu res therof . As examples of C- c alkanoic acids may be mentioned the same as above, acetic acid being preferred for the reasons given . The ratio between formic acid ions and C- c alkanoic acid ions may be as de¬ scribed above. I n the composition of the invention , the concentrations of the various metal ions may vary widely according to whether the composition is a concentrate or is ready for use. The concentration ready for use will vary according to crop, amount of metal to be applied, application form and equipment etc. and the determination of the ready-use concentration is easily carried out by a person skilled in the art. However, the following concentrations ranges are given as illustration : Mn 0.01 -10% by weight; Fe 0.01 -10% by weight; Cu 0.01 -12% by weight; and Zn 0.01 -12% by weight calculated on the total composition , the highest parts of the ranges applying mainly to concentrates . Concen- > trates are usually diluted with water prior to application . The composition may further contain NH~, the concentration being e. g . as described above. BRI EF DESCRI PTION OF THE DRAWI NGS Fig . 1 shows plots of plant dry weight versus time for sugar beet, rapeseed, and oats obtained in the growth test in example 4 below . The plots show the development of unsprayed controls with (•) and without (o) access to manganese in the substrate; plants sprayed with the composition of example 2 (in diluted form) both with (A) and without (Δ) access to manganese in the substrate; and plants sprayed with a conventional chelated manganese composition both with (■) and without C Q ) access to manganese in the substrate. The unsprayed controls are connected with dotted lines . The ordinate scale is 0-0.3 g for sugar beet and 0-0.6 g for rapeseed and oats . Fig . 2 shows plots of manganese content versus time in the test obtained in the test in example 4, the manganese content being ex¬ pressed as vg Mn per g plant dry matter. The symbols are the same as in Fig. 1 . The invention is illustrated by the following non-limiting examples . EXAMPLE 1 66.66 g technical grade MnCO- (containing 45% Mn) and 100 g 85% formic acid were mixed with 800 g water and boiled for about one hou r until all CO~-evolution had ceased and all solid material was dissolved, and until the solution assumed a bright pink colour. Thereafter, water was added to the solution up to a total weight of 1000 g . This gave a solution of manganese( l l ) formiate containing 3% by weight of manganese. The concentration was confirmed by means of atomic absorption analysis . EXAMPLE 2 44.44 g technical grade MnCO- (containing 45% Mn) and 43.3 g 85% formic acid were mixed with 800 g water. -The mixture was refluxed until all CO~-evolution had ceased and all solid material was dissolved, and until the solution had assumed a bright pink colour. Water was added to the solution up to a total weight of 1000 g . This gave a solution of manganese( l l ) formiate containing 2% by weight of manga¬ nese. The concentration was confirmed by means of atomic absorption analysis . EXAMPLE 3 11 .33 kg MnO, 24.00 kg acetic acid (98% by weight) , and 0.54 kg formic acid (85% by weight) were mixed with 61 .73 kg water and stirred and warmed slightly until all solid material had dissolved, and until the solution had assumed a pink colour. Thereafter, 2.4 kg aqueous ammonia solution (25% by weight) was added giving 100 kg of a solution containing 8% by weight of manganese. The solution is stable and miscible with various herbicides such as oxytrile without the herbicide separating out from the solution . EXAMPLE 4 Plant growth experiments I n the present Example the ability of a micronutrient metal composition according to the invention to supply manganese to plants is compared with that of an EDTA-chelated manganese product. Two dicotyledonous plants (sugar beet, variety Primahill from Hilleshδg AB, Hilleshδg, Sweden , and spring rapeseed, variety Topas from Svalδf AB, Svalδv, Sweden) and a monocotyledonous plant (oats, variety Vital from Svalδf AB, Svalδv, Sweden) were used as test plants . Unpelleted sugar beet seeds and seeds of rapeseed and oats were sown di rectly into trays with a peat/sand substrate (volume ratio 2: 1 ) . The first four days the trays were covered with black plastic film in order to prevent evaporation and consequent desiccation of the seeds . Fu rthermore, the light in the cultivation room was turned off during this period . The growth substrate initially contained 17.5 g dolomite per litre of peat/sand mixtu re, giving a pH in the root medium of 6.5. The pH was chosen so as to make it possible to produce plants with a manga- nese deficiency since the probability of a manganese deficiency in the growth tissues increases significantly with increasing pH at pH values above 5 due to fixation of available manganese in forms not accessible to the plants . The peat/sand mixture initially contained about 1 .3 mg manganese per litre of substrate. The plants were grown at 18±1 °C. The relative humidity around the plants was 65±5%. The plants were illuminated for 16 hours per day with Philips 400 W mercury lamps giving a illumination intensity on 2 the leaves of 80-90 W/m . Apart from this, a certain amount of daylight illumination was allowed. The plant material was circulated in the room during the growth period in order to avoid "rim effects" and the possible influence of other growth conditions . Thinning out of the plants took place after 10 days . Nutrition was supplied to the plants twice a week with solutions with and without manganese sulfate in order to produce plants without (controls) and with manganese deficiency respectively. The com- position of the nutrition solutions is given in Table 1 below. In each application, 1 litre of solution was given to each plant tray. Further¬ more, the plants were watered with distilled water 3 times a week (always the same amount per tray) . The plants were grown in the room for two months under the conditions specified whereby half of the plant material was regularly supplied with manganese via the substrate during the entire period while the ofcher half did not receive manganese at all in this manner. Thus, the latter plants only had access to the approximately 1 .3 mg manganese per litre of substrate present from the beginning . Of this amount, probably only a minor part was accessible to the plants in the form of 2+ Mn since pH around the roots was above 6. Leaf spraying Spraying of the parts of the plants above the soil with two fertilizing compositions was for each plant species carried out at occasions during the growth period . AH leaf sprayings were carried out when the plants were 4, 6, and 8 weeks old respectively. Manganese was supplied to the sprouts through spraying with dilutions of the product according to Example 2 (stock solution containing 20 g/l) and manganese chelate (from Rexolin Chemicals AB Helsingborg, Sweden , containing Mn 80.4 g/l) . Solutions with a manganese content of 20 mg/l were prepared from the two fertilizing agents . This cor¬ responds to the manganese concentration normally supplied to crops in the field. The plants were sprayed with the respective agents by means of plastic spray bottles. The spraying of the plants was continued until the leaves appeared thoroughly wet. During each leaf spraying process, the substrate was covered with black plastic film so that no solution could be supplied directly to the plants via the roots . After an hour, the plastic film was removed . Thus, a minor amount of manganese composition that has run down the leaves may, on a long-term basis, have been absorbed via the roots . 24 hours after the spraying, the parts of the plants above soil level were cut off. Fresh and dry weights as well as manganese content in the plants were determined for six parallel samples . The plants were also recorded photographically. Results All three plants species were inhibited in their development due to the manganese shortage in the root medium (fig . 1 ) , and in particular the rapeseed was growing poorly du ring the entire growing period . Symptoms of manganese deficiency were developed in particular with sugar beet and rapeseed, while to a far less extent with oats . Sugar beet leaves with manganese deficiency became chlorotic compared to the controls that continuously received manganese via the substrate. Leaf spraying with manganese (20 mg/l) gave a growth stimulating effect, in particular on rapeseed . The two tested leaf spray fertilizers had similar growth increase effects on the various test species during the enti re growth period . The manganese content in the parts of the plants above the soil is generally low for all three species (fig . 2) . The internal manganese content in growth tissues that are considered to correspond to the requirement is between 40 and 100 μg per g dry matter. The de¬ ficiency limit is 20-30 μg per g dry matter. The manganese content in sugar beets that have been grown with continuous access to man¬ ganese does not exceed 60 μg per g sprout dry weight. For rapeseed and oats, the manganese content in the sprouts varies between 30 and 40 μg per g sprout dry weight. The low manganese levels in the plants are considered to be due to the fact that a part of the exter¬ nally supplied manganese has not been accessible to the plants i . a . because of the high pH value in the substrate (initially 6.5) . The content of manganese in plants grown without external supply of manganese during the growth period is in all plants lower compared to the manganese levels in the control plants, in particular for sugar beet and rapeseed on days 43 and 57. Leaf spraying with a composition according to Example 2 diluted 200 x with water and EDTA-chelated manganese respectively only affects the manganese content in the control plants to a very small extent. Con¬ versely, both leaf spraying compositions give a marked increase of the manganese content in sprouts from plants grown in a practically manganese-free medium (in itially about 1 .3 mg Mn per litre of sub¬ strate) . The effects of the composition' according to Example 2 and chelate do not differ significantly. From the above results it may be concluded that the method according to the invention is as efficient in remedying manganese deficiency as the chelated manganese compositions currently available. Table 1 Composition of nutrient solutions for the cultivation of sugar beet, rape seed and oats . I n the manganese-free solutions, MnSO 4 was excluded . Macrosalts g per 10 I sol ution MgSO 4 x 7H 2 O 7.41 K 2 H PO 4 8.84 KH 2 PO 4 4.00 Fe-versenate 0.28 NH 4 CI 3.20 NH 4 NO 3 5.00 Ca (NO 3 ) 2 x 4H 2 O* 15.00 Na 2 SO 4 1 .07 Na*NO 3 5.44 g per liter of Microsalts stock solution ** CuSO 4 x 5H 2 O 0.20 ZnSO 4 x 7H 2 O 0.004 NH 4 ) 6 Mo y O 24 x 4H 2 O 0.004 H 3 B0 3 °- 62 MnSO 4 x H 2 O 2.00 * Dissolved separately and added after pH of the other dissolved n utrients Cmacro and micro) had been adj usted to 6.0 by means of HCI . ** 10 ml of stock solution was used for 10 I final nutrient sol ution .

Claims: CLAIMS 1 . A method for supplying a micronutrient metal element to a plant comprising administering to the plant a micronutrient composition containing cations (A) which are selected from Mn ions or Fe ions or mixtures thereof as well as anions which are formate ions and optionally ions of a C 2 5 alkanoic acid or a mixtu re of such acids . 2. A method according to claim 1 in which the micronutrient composi¬ tion is an aqueous solution . 3. A method according to claim 1 or 2 in which the composition further contains cations C B) selected from Cu ions and Zn ions and mixtures of such ions . 4. A method according to claims 1 -3 in which the C 2 5 alkanoic acid is acetic acid . 5. A method according to claims 1 -4 in which the molar ratio between tthhee ffoorrmmaattee iioonnss aanndd ttlhe ions of the C^ c alkanoic acid is in the range from 1 : 1000 to 1 :0. 6. A method according to any of the preceding claims in which the cations (A) are Mn ions . 7. A method according to any of the preceding claims in which the micronutrient composition further contains NH« . 8. A method according to claim 7 in which the concentration of NH- is up to 4 molar equivalents per molar equivalent of the cations CA) and optionally (B) . 7. A method according to claim 6 in which the micronutrient composi- tion is administered in an amount corresponding to 25-400 g Mn/ha, preferably 50-300 g Mn/ha, in particular 100-200 g Mn/ha such as 160 g Mn/ha. 8. A method according to all the preceding claims in which the plant to which the micronutrient metal element salt is administered, is sugar beet, wheat, rye, barley, oats, maize, millet, grapes, citrus trees, apple, pear, apricot, cherry, plum, peach , rose, or grass . 9. A method according to all the preceding claims in which the micronutrient metal element salt is administered by leaf spraying . 10. A method according to all the preceding claims in which the micronutrient metal element salt is administered in combination with an agent selected from herbicides, pesticides and growth promotors . 11 . An aqueous micronutrient metal element salt composition in which the cations (A) are selected from Mn ions or Fe ions or mixtu res thereof, and the anions are formate ions and optionally ions of a C- e alkanoic acid or a mixture of such acids . 12. A composition according to claim 11 which contains fu rther cations CB) which are selected from Cu ions and Zn ions and mixtu res thereof . 13. A composition according to claims 11 or 12 in which the C. ,. alkanoic acid is acetic acid . 14. A composition according to any of claims 11 -13 in which the molar rraattiioo bbeettwweeeenn tthhee ffoorrmmaattee iioorns and the ions of C 2 _ 5 al kanoic acid is in the range from 1 : 1000 to 1 : 0. 15. A composition according to any of claims 11 -14 in which the cations (A) are Mn ions . 16. A composition according to any of claims 1 1 -15 which fu rther contains NH., . 17. A composition according to claim 16 in which the concentration of NH 3 is up to 4 molar equivalents per molar equivalent of the cations (A) and optionally CB) . 18. A composition according to any of claims 11-17 in which the concentrations of the cations, if present, are in the following ranges: Mn 0.1-10% by weight; Fe 0.1-10% by weight; Cu 0.1-12% by weight; and Zn 0.1-12% by weight calculated on the total composition.

Inventors: PETERSSON JAN, VON MAGIUS NIELS WILHELM, PETERSSON, JAN, VON MAGIUS, NIELS, WILHELM
Applicants: PERSTORP AB
Application year: 1986
Main classification: C05D9
IPC codes: C05D9