United States Patent Office Patiented Alig
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2,950, 183 United States Patent Office Patiented Alig. 23, 1960 2 compatibility between ammonium phosphate solutions and the trace elements iron, manganese and/or copper, 2,950,183 so that these trace elements can be added to the solu tion to form a single spray. NURENT SPRAY COMSPOSITION FOR P:ANTS 5 It is important in sprays for foliar treatment that the Alexander A. Nikitin, College Park, Charies C. Fite, Jr., above trace elements be in divalent form (monovalent East Point, aad Janet Segers Gary, Union City, Gay in the case of copper). In the first place, plants ab assignors to Tennessee Corporation, New York, N.Y., sorb, translocate, and assimilate the trace elements much a corporation of New York more readily in this form-than in their oxidized states of O higher valency. In the second place, oxidation of the No Drawing. Fied Mar. 24, 1958, Ser. No. 723,216 trace element ions to states of higher valency results in 12 Claims. (C. 7F-11) precipitation of solid materials which interfere with the operation of the spray equipment, form undesirable spray residues and cause scale infestation on fruits, This invention relates to nutrient spray, such as liquid 15 etc. No difficulty arises with zinc from the standpoint fertilizers and trace element solutions, for application of oxidation, because zinc remains in the divalent form to growing plants. and has no effect on any other trace elements which may It is well known that various so-called trace elements be present. But there is a strong tendency for fer are necessary for healthy plant growth, in addition to rous, manganous and cuprous ions to oxidize to higher - the usual nitrogen, phosphorus, and potassium fertilizer 20 states of valency in ammonium phosphate solutions with materials. Lack of adequate supplies of these trace the objectionable results already stated. elements in the soil is scnetimes a matter of local soil Moreover, although the manganous ion, Mint, is composition, but more often is due to depletion result commonly much more stable than the ferrous ion, Fet, ing from such causes as excessive liming, leaching by ex once manganese becomes oxidized it then exerts a pow cessive rainfall, immobilization of trace elements as 25 erful oxidizing action on iron. Thus it is known that the result of low moisture, intensive cropping, etc. Chlo ferrous ion, Fett, is much more readily oxidized in the rotic conditions resulting from such deficiencies are a presence of manganese than when iron is used alone. common occurrence during the growing season unless the in view of these facts, the established practice has been eficiencies are corrected, preferably by the use of sprays to use iron and manganese at the very high ratio of 3-10 containing the desired trace element or elements since 30 parts by weight of ferrous sulphate to one part man foliar treatment is both convenient and most effective. ganous sulphate, depending upon the crops and Soils Usually the trace elements are provided in the form of treated. This high ratio of iron to manganese has been sulfates, but other Water soluble salts can be used in required to compensate for the iron which was lost due stead Such as chlorides, nitrates and acetates. to oxidation by manganese and precipitation as ferric Obviously the trace element or elements required, as oxide (FeO3), which is inert and has no nutritional well as the amount to be supplied, may vary from one value. In addition, the inert ferric oxide builds up a Soil type to another and also with different crops. Among heavy residue which interferes with the spray applica the trace elements that need to be supplied for healthy tion by plugging the spray nozzles. Ferric oxide also plant growth may be mentioned iron, manganese, zinc, causes high scale infestation on citrus fruits which greatly copper, boron, molybdenum, etc. Iron, manganese, zinc 40 depreciates their value. Still further, iron is usually sup and copper are commonly regarded as the essential plied in the form of ferrous Sulphate (FeSO4), and in nutrient trace elements and requirements for thern have this case its oxidation from ferrous to ferric results in been definitely established for most soil types. Boron the liberation of excess sulphate ion which is injurious and molybdenum can be safely used only in extremely to foliage. Small concentrations governed by the character of the The aforesaid incompatibility of divalent iron and Soil, Such as heavy clay, sandy loam, muck soil, etc., and 45 manganese and monovalent copper. With ammonium phos by the type of crop. phate solutions results from the high alkalinity of these it is highly desirable in the interest of saving time, solutions which causes oxidation and resulting precipi iabor, and expense to Inake each spray application serve tation of trace elements. This alkalinity is also detri as many purposes as possible. Thus not only the trace mental to many organic pesticides, causing their de element or elements but also nitrogen, phosphorus and/or 5 composition. Of course, the alkalinity can be reduced potassium fertilizer materials are desirably incorporated by adding an acid which is suitable for use in a plant in the Spray liquid, and sometimes also one or more spray, such as phosphoric acid, but the trace elements pesticides, provided of course that the several materials are not stabilized against the oxidation which would take are all compatible with one another. For example, i, place as the result of high alkalinity of diammonium Soluble potassium Salts such as potassium chloride can phosphate solutions, unless the pH of these solutions is be added to the spray solution as a source of potassium So low (e.g., 4.1-4.7 or even less; see Table I) as to be along with Suitable trace element compounds. But di very injurious to plant foliage. In fact, while some orna aminonium phosphate, which is widely used in liquid mental plants such as laurel can tolerate a solution fertilizer sprays as a source of both nitrogen and phos having a pH range as low as 5.5-6.1, for most plants the phorus, is incompatible with certain of the trace elements O pH value should preferably be between 6.1 and 7.0. and also with certain pesticides and cannot be mixed The present invention is based on the discovery that directly with them in the same spray. The same in the trace elements iron, manganese, zinc and copper compatibility exists in sprays to which phosphoric acid are rendered compatible with ammonium phosphate so and ammonia have been added, these materials being lutions, and three of these trace elements-iron, man ganese and copper-are retained in the state of lower precursors of monoamimonium and diammonium phos Valency, either alone or in combination, by the addition phate. For convenience, these materials are referred to Such solutions of appropriate amounts of oxalic acid or to generically as "ammonium phosphates' and the sprays soluble oxalates, while at the same time the pH values as "ammonium phosphate solutions.” of the solutions can be obtained in as high a range as The chief object of the present invention is to pro 70 pH 6.1-7.0, a range which is entirely safe for application vide an effective and suitable solution of the problems of to plant foliage. The results obtained with oxalic and - - - - - - a -s. 2,950,188 3 - 4 phosphoric acids are set forth for comparison in the character of reaction of the final solution was held within following Tables I and II: the limits of pH 6.1-7.0. The upper or lower limit of pH value, or some intermediate value, may be utilized - . TABLE I most effectively for determining the correct proportions The effect of oxalic acid on the availability of trace 5 of materials to be used in preparing the desired spray elements (Fe, Mn, and Zn retained in divalent form) solution depending upon the particular trace elements in diammonium phosphate solution, at various pH used. For instance, Table I shows that iron retains its values m chemical stability in divalent form even at the higher pH values shown in Table III, whereas for manganese Percent Availa O it may be necessary to reduce the pH to the lower value 75% Oxalic bility . - shown in Table III (pH 6.1). Thus the pH to which the - Acid (gm.) pH - - - Materials Used final spray is to be adjusted will depend upon the trace Fe ... Mr. Zn elements that may be used, and the amount of Oxalic acid to be used may be determined accordingly as shown wes - a as resa as 8.0 9.16.67 - 5.9 FeSO4.7Ho (22% Fe) at 5 5 by Table III. For example, if a pH of 6.5 is desired, a - g:liter. sufficient amount of oxalic acid should be used to pro 6------------ 7.2 18.2 6.67 5.9 M.52.gilter. Hao (30% Mn) at 5 2----------- 6.8 36.4 6.67 5.9 ZS2.0 (34% Zn) at 5 vide the ratio 100:18. - - - . g.fter. Oxalic acid, when used to obtain the range of pH :18----------- 6.5 86.0 6.67 11.8 (NH);HPO (21% N; 53% - - PO) at 100 gliter. of the final spray solution containing trace elements and 24----------- 6.2 : 00 - 6.67 - - 23.5 75%ÖaicVarious quantities,Acid HCO2Ho, as shown 20 diammonium phosphate as shown in Tables I and III, in Table. i.e., pH 6.1-7.0, makes iron, manganese, copper and 00 33.3 70.6 zinc compatible individually or together with ammonium 100 64.0 94.