GB803052A - Compositions for improving the soil - Google Patents

Abstract

The invention comprises mixtures of the following compounds with their iron chelates: AXN-(alkylene-NX-)n-alkylene-NBX, where alkylene (which includes cyclohexylene) has at the most 7 carbon atoms and interposes 2 or 3 carbon atoms between the nitrogen atoms, X is CH2COOH or CH2CH2COOH or an alkali metal or ammonium salt thereof, A and B are as for X or are hydrogen, alkyl or aralkyl, optionally substituted by hydroxy, alkoxy, carboxylic acid or ester, mercapto, phosphonic acid or sulphonic acid, and n is 0-4. The mixtures are obtained by treating the compounds (made e.g. as in Specification 600,629) with a suitable amount of an iron compound, especially iron phosphate. An example is given of the preparation of ethylenediamine tetraacetic acid and its reaction with ferric phosphate, followed by addition of sodium hydroxide to raise the pH of the solution to 4.5. The product can be obtained in solid form by evaporation or precipitation with alcohol, and in this case contains phosphate as well. Other specified chelating agents are N-(b -hydroxyethyl)-ethylenediamine triacetic acid, N : N1 - di - (b - hydroxyethyl)-ethylenediamine diacetic acid (and mixtures of these two), isopropylenediamine tetraacetic acid, diethylenetriamine pentaacetic acid, and other compounds derived from triethylenetetramine, tetraethylene and pentaethylene amines, A being H, b -hydroxyethyl, b -methoxyethyl, b -phenylethyl, b - mercaptoethyl, g - mercaptopropyl, carboxymethyl, b - carboxyethyl, b -carbethoxyethyl, b - sulphoethyl or b - phosphonoethyl. Specification 768,238 also is referred to.ALSO:The invention comprises a composition of a chelating agent as defined below mixed with its iron chelate, (1) alone or with an inert carrier, as an additive to correct iron deficiencies in soil, (2) mixed with a porous mineral carrier and nutrient elements as a medium for the hydroponic cultivation of plants, or (3) mixed with a fertiliser such as garbage, sewage sludge, animal residues, blood, proteinaceous matter, artificial manure, compost or mixture thereof. The chelating agent is of the formula:-AXN-(alkylene - NX -)n - alkylene - NBX, where alkylene (which includes cyclohexylene) has at the most 7 carbon atoms and interposes 2 or 3 carbon atoms between the nitrogen atoms, X is CH2COOH or CH2 CH2COOH or an alkali metal or ammonium salt thereof, A and B are as for X or are hydrogen, alkyl or aralkyl, optionally substituted by hydroxy, alkoxy, carboxylic acid or ester, mercapto, phosphonic acid or sulphonic acid, and n is 0-4. The compositions are made by treating the chelating agent with a suitable amount of an iron compound; iron phosphate is preferred as the resulting mixture contains phosphoric acid as well. The free chelating agent acts as a buffer to stabilize the pH (cf. Specification 768,238) and is preferably present in a minor proportion, e.g., 5 per cent, but this may be varied (up to 95 per cent), to control the pH and improve the availability of other trace metals in the soil. Phosphates are also solubilised and made assimilable, and when the chelating agent is used as its ammonium salt nitrogen is supplied as well. For application (1) the compositions may be applied in powder, liquid or paste form, alone or with a synthetic nutrient or conditioning agent (e.g., polyacrylonitrile), or on a carrier such as vermiculite; it is preferred to add the hot carrier to a concentrated solution of the composition and dry the slurry so obtained. Vermiculite is also the preferred carrier for (2) but there may also be used similar materials such as alumina, silica gel or dry clay. Specified nutrients for these compositions are magnesium sulphate, calcium phosphate, calcium sulphate, potassium nitrate, potassium chloride and urea. Fertilizers containing the compositions as in (3) may be inorganic or organic, examples of the former being calcium phosphate (e.g., as bonemeal) and iron phosphate, with or without one of the carriers specified under (2). The organic fertilizer may be sewage sludge, sheep or cow manure, soybean meal, cottonseed meal, or fermented and dried vegetable matter. Inorganic nutrients may be added to these if necessary. The preferred chelating agents are ethylenediamine tetracetic acid, N-(b -hydroxyethyl) - ethylenediamine triacetic acid, N : N1 - di - (b - hydroxyethyl) - ethylenediamine diacetic acid or mixtures of these, but several others are specified as suitable. Specification 600,629 [Group IV(b)] also is referred to.