LIQUID PHOSPHATE PLANT NUTRIENT COMPOSITONS AND METHOD OF PREPARATION THEREOF

Abstract: Processes for preparing liquid plant nutrient compositions by the reaction of phosphoric acid and sources of ammonia, the resultant products having predetermined compositional ratios of nitrogen and phosphates. Also, processes for preparing such liquid plant nutrient compositions incorporating humic acids and chelated humic acids useful in modifying plant growth.

Description: LIQUID PHOSPHATE PLANT NUTRIENT COMPOSITIONS AND METHOD OF PREPARATION THEREOF DESCRIPTION 1. Technical Field The present invention relates to liquid compositions incorporating phosphates having utility as plant nutrient compositions. The present ivention further relates to novel processes for preparing such compositions which have high availability to plants as well as a high degree of compatibility with minor nutrients. 0 2. Background Art The use of phosphate-based compositions and mixtures as fertilizers and plant nutrients has long been known. However, the processes heretofore employed for the production of phosphate compositions are 5 typically expensive with regards to the chemicals utilized as reactants, as well as the apparatuses employed for carrying out the reactions. By way of example, many conventional processes utilize "green" phosphoric acid in pipe reactors, with the reaction 20 being carried out at temperatures in the range of from about 600°F to about 800°F. Moreover, most such conventional processes result in a product which contains a substantially high percentage content of polyphosphates. 25 It is well known that conventionally prepared orthophosphate solutions have limited compatibility with minor nutrients such as iron, zinc, manganese and copper unless the minor nutrients are chelated with synthetic chelating agents. However, such synthectic 30. chelated minor nutrients are substantially ineffective when applied to plants in a foliar application and are only limitedly effective when used in soil applications. Minor nutrients chelated with organic chelating agents, however, have been shown to be compatible with solutions containing approximately 15 to 20 per cent polyphosphate and 80 to 85 per cent orthophosphate. The organic chelates are much more readily available to plants through both foliar and soil applications than are minor nutrients chelated with synthetic chelating agents. It is also known that most plants can usually assimilate only orthophosphates, rather than chained polyphosphates. Moreover, the presence of calcium in the soil environment or in the water used for irrigation or other watering of the plants tends to cause the precipitation of much of the phosphate into the soil, thus significantly reducing the amount of phosphates available to the plants. Accordingly, it has long been known that it would be desirable to have a process for preparing liquid phosphate compositions useful in a wide' variety of agricultural and horticultural environments wherein the phosphates contained int he composition are readily available to plants through foliar and soil application and the composition is characterized by a high degree of compatibility with minor nutrients. Moreover, it has long been known that it would be desirable to have such a process which can utilize readily available and relatively inexpensive reactants, and which can be carried out more rapidly than heretofore possible to produce stable end products resistant to separation during storage or precipitation in the presence of environmental calcium. DISCLOSURE OF THE INVENTION Therefore, it is an object of the present invention to provide improved processes for producing liquid phosphate compositions having utility as plant nutrients and growth modifiers. Accordingly, the preferred methods disclosed herein are capable of being carried out relatively inexpensively while remaining useful to produce compositions having desired percentages by weight of nitrogen, phosphorous and potassium for use in a wide variety of plant growing applications. Further, the processes disclosed herein are adapted to produce phosphate liquids having enhanced storage capabilities and, further, are stable against precipitation in the presence of environmental calcium. Further still, the processes hereof are adapted to produce compositions which exhibit a high degree of availability to plants on which they are applied and a ready compatibility with a variety of minor nutrients. These and other features and advantages will become apparent by reference to the accompanying descriptions. BEST MODES FOR CARRYING OUT THE INVENTION The processes of the present invention provide generally for the reaction of phosphoric acid and ammonia or aqua in an aqueous medium, with the temperature of the reaction medium maintained preferably below 210°F ( 99 °C). The processes of the present invention are adapted for use in preparing liquid compositions having utility as plant nutrients and growth modifiers. The processes surprisingly and unexpectedly result in the production of phosphate- based liquids having predetermined ratios of nitrogen an phosphorous, as well as potassium and humic acids. The phosphate-based liquids so prepared are inexpensive to produce and are characterized by their adaptability for prolonged storage without separation. Further, the compositions are readily available to plants to which they ' are applied by either foliar or soil application, and they have a high compatibility with minor nutrients such as zinc, manganese, iron and copper. Organic phosphates are produced by the processes described in greater detail below. Generally, for foliar applications, the products produced are adapted to be used with dilution; when used for soil application, they are adapted for use without dilution. Foliar application of the organic phosphates produces little or no burning of the plant and results in translocation of the nutrient chemicals throughout the plant system more rapidly than via soil application. Importantly, the organic phosphates are stable in soil and have little or no tendency to precipitate in the presence of calcium. Thus, the organic phosphate solutions produced are believed to be 2 to 3 times more efficient in their uptake than inorganic forms. In the manufacture of the organic phosphates using the processes of the present invention, it is preferable that chelated humic acids be used when and as called for by the process. In carrying out the processes of the present invention, reaction vessels of suitable volume and construction are chosen to provide adequate mixing of the reactants as well as cooling of the reaction medium. The reactions of the processes are carried out in an aqueous medium in the reaction vessel. Aqua or an aqueous ammonia solution are introduced into the reaction medium in volumes determined in part by the desired final percentage of nitrogen in the reaction product. Super green or white phosphoric acid, preferably having a strength of approximately 70 % phosphate radical, is reacted with the ammonia or aqua. The volume by weight of the phosphoric acid employed is determined, in large part, by the desired ratio of phosphate to nitrogen in the end product of the process. Potassium hydroxide is utilized ' in predetermined proportions as a source of potassium for the products produced by the processes hereof . The reactions of the processes of the present invention are largely exothermic, and it has been surprisingly and unexpectedly discovered that it is preferable that the reaction medium be maintained at a temperature no greater than 210°F ( 99 °C) and, preferably, lower than 205°F ( 9β°C) during the reaction cycle. Accordingly, it is desirable that a reaction vessel be chosen or constructed having adequate cooling means for use in carrying out the processes of the present invention. Further, it has been discovered that it is highly desirable to maintain the pH of the reaction mixture within about a point of neutral during the reaction cycle. In further variations of the processes of the present invention, liquid humic substances are reacted in the aqueous medium and are injected with the phosphoric acid to yield organic phosphate compounds. During the reaction cycle, chelated organic acids are introduced to the reaction medium. The resultant organic phosphates are unexpectedly exceedingly stable against separation during storage and are readily available to plants on which they are applied. It is believed that the liquid humic substances react with and join to the ammonium phosphate molecules produced during the reaction to yield a multitude of organic phosphate molecules of differing structures and molecular weight. In order to more fully disclose the processes of the present invention, attention is invited to the following examples, which are to be considered illustrative only and not limiting in any sense. EXAMPLE 1. PROCESS FOR PREPARING AMMONIUM PHOSPHATE LIQUIDS. The process of the present example is adapted for use in the preparation of ammonium phosphate liquids having a relatively high orthophosphate content and relatively low polyphosphate content. Stated percentages represent percentage by weight, unless otherwise indicated. In carrying out the steps of the process of the present example, a suitable reaction vessel is first chosen. Approximately 10% (ten percent) by weight of water is introduced into the reaction vessel to constitute an aqueous reaction medium. Next, a solution of either aqua or ammonia dissolved in water is prepared having a total nitrogen content largely dependent upon the desired proportions of nitrogen and phosphorous in the product resulting from the process. For purposes of this example, a desired final ratio of 8 parts nitrogen to 24 parts phosphorous in the form of phosphate is chosen. Thus, if aqua is chosen for preparation of the solution, a nitrogen content in the solution of approximately 20 % (twenty percent) or, very roughly, 24.4 % NH3, is used. On the other hand, if ammonia is used for preparation of the solution, it is preferable that the solution have a strength of approximately 82% NH3. Subsequently, the ammoniated solution is introduced substantially simultaneously with a solution of super green phosphoric acid having a phosphate titer of about 70% into the reaction vessel. For the example chosen, wherein phosphates comprise approximately 24% of the resulting composition, approximately 34.3 % by weight of green phosphoric acid is introduced into the reaction mixture. The reaction cycle then commences and the pH is monitored and adjusted as necessary to preserve a pH during the reaction cycle in the reaction medium of between about 6 and 8, and , preferably, betwen about 6.5 and 7.5. Further, it is preferable that the temperature be kept below 210'F ( 99'C) throughout the reaction cycle, as previously discussed. During the reaction, circulation of the reacton mixture is desirable to insure complete reaction and to prevent precipitation. Water is added as necessary to maintain a correct volume in order to obtain the desired final proportional weight ratios of nitrogen to phosphorous. Surprisingly and unexpectedly, it has been discovered that it is desirable in carrying out the process of the present example to produce a liquid ammonium phosphate composition having a ratio of nitrogen to phosphate in the range of from about 1 to 3 to 1 to 3.3. Such ranges result in products having extremely beneficially low salting out temperatures. However, where the products of the present process are to be used in an environment in which salting out temperatures are not critical, the range of ratios obtainable can be widely varied to suit a particular agricultural or horticultural requirement. In carrying out the process of this example, wherein aqua is used and the final ratio obtained is approximately 8 to 24 (nitrogen to phosphate), the following weights of reactants are illustrative of those which would result in a 2,000 pound batch of final product: Aqua - 800 pounds; water - 514 pounds; and 70% strength green phosphoric acid - 686 pounds. If, on the other hand, a similar end-product ratio of 8 to 24 is desired, the process of the present example can be carried out substituting ammonia (82% strength) for aqua by providing the following weights of initial reactants to produce an illustrative 2,000 (two thousand) pound batch: ammonia - 195 pounds; water - 1,119 pounds; and phosphoric acid (70% titer) - 686 pounds. The process of the present example results in a product having a relatively high orthophosphate content and a relatively low polyphosphate content. Further, particularly as compared to typical conventional commer ci al methods of pr epar ing predom inantly polyphosphate liquid products, the process of the present example should, in a commercial embodiment, resul t i n s igni f i cant cost savings . The product produced by the process has excellent compatibil ity with ι?,,inor nutrients, such as zinc, manganese, iron, and copper. In part, this is believed due to the presence of polyphosphates in the final product. Moreover, the compositions produced by the process hereof are substantially free of formation of precipitate and gel when the products are batch mixed. Finally, the process of the present example produces products having a high availability to plants as compared to conventional products having relatively higher polyphosphate content. EXAMPLE 2. PROCESS FOR PREPARING LIQUID POTASSIUM-AMMONIUM PHOSPHATE COMPOSITIONS The process of this example is adapted for use in the preparation o.f liquid compositions having predetermined ratios of nitrogen, phosphorous, and potassium. The resulting products are useful as plant nutrients for either foliar or soil application. Moreover, the resultant products have a relatively high compatibility with minor nutrients as compared with compositions heretofore known, due to the relatively lower percentages of orthophosphates in the resulting product. For purposes of the present example, the process is described in reference to the preparation of a liquid composition having a ratio of nitrogen to phosphorous to potassium of 9:18:9. However, it will be recognized that the percentages and weights set forth herein are illustrative only and can be varied substantially to obtain desired ratios among the nitrogen, phosphorous and potassium within the scope of the present invention. In carrying out the process of the present example, an appropriate reaction vessel is once again selected. A volume of water representing approximately 10% (ten percent) by weight of the desired volume of resultant product is introduced into the reaction vessel. Next phosphoric acid and potassium hydroxide are substantially simultaneously introduced into the reaction vessel. For the preparation of the product of the process of this example having an analysis of 9:18:9, a 50% strength potassium hydroxide soluton containng approximately 42% K20 and representing approximately 21.6% of the total volume by weight of the resulting product is chosen. Super green phosphoric acid having a strength of approximately 70% is introduced into the reaction medium in an amount equal to about 25.8% of the total final volume by weight. The pH of the reaction medium is preferably maintained in a range of between 6.5 and 7.5 during the entire reaction cycle. It has been discovered that, unexpectedly, substantial deviation from such pH range can result in precipitation of an aluminous gel, if the reaction medium is too acidic, or an undesirable ammonium phosphate if the mixture is too alkaline. Next, aqua having a strength of approximately 20% or ammonia having a strength of approximately 82% is injected to maintain the pH between 6.8 and 7.5 and to provide a source of nitrogen for the reaction product. In the present example, the aqua or ammonia in injected until approximately 4.4% of nitrogen by weight is added to the total weight of the reaction medium. Preferably, at all times the temperature of the reaction mixture is maintained below 210°F ( 99 °C) . The final desired weight of nitrogen in the reaction product is adjusted by the addition of dry urea until the appropriate percentage by weight is obtained. The reaction cycle is allowed to continue until completion. Water is added as necessary to maintain the desired volume. It is preferable that the entire mixture be circulated continuously throughout the process to insure complete reaction and to minimize precipitation. Further, it has been surprisingly discovered that it is desirable to force air through the reaction medium during the reaction process. With proper temperature maintenance in accordance with the foregoing, and with agitation of the reaction medium, a 2,000 pound total reaction product weight can be obtained within four hours or less. It is recognized that the overall reaction time will vary with the volume of product desired to be produced. EXAMPLE 3. PREPARATION OF AMMONIUM PHOSPHATE LIQUID COMPOSITIONS INCORPORATING HUMIC ACIDS The process of the present example results in the production of liquid ammonium phosphate compositions having many of the desirable properties of the compositions of the foregoing examples while providing the added desirable benefit of incorporating relatively high concentrations of liquid humic substances into the reaction product. The product so produced has little or no tendency to separate during even prolonged unattended storage. Further, the resultant composition is readily available to plants on which it is applied. Moreover, the freezing point of the resulting composition is approximately 10 °F ( -12 °C) lower than many commercially available conventional phosphate compositions. For illustrative purposes, the process of the present example is described hereafter in reference to the preparation of a composition having a nitrogen to phosphate ratio of 8:24. It will be recogni'zed that such ratio and the following example are illustrative only and are not limitative with regards to the concepts of the present invention. In carrying out the process of the present example, a suitable reaction vessel is chosen and a volume of water substantially equivalent to 10% by weight of the desired final volume of the product is introduced into the vessel to constitute an aqueous reaction medium. Next, a 20% aqua solution is mixed with a liquid humic acid composition of any available commercial origin. However, preferably, the humic substances chosen are comprised primarily of relatively smaller weight humic acid fractions. The aqua, in the present example, comprises approximately 22% of the total volume by weight of the reaction mixture. The liquid humic substances can comprise approximately 3 to 10% of the total volume, by weight, as desired. After mixing the aqua and liquid humic substances, the resulting mixture is injected into the reaction medium substantially simultaneously with a volume of 70% green or white phosphoric acid totalling approximately 34.3% of the overall reaction mixture volume. While the reaction takes place, the pH of the reaction medium is preferably maintained between about 7 and 7.5 during the entirety of the reaction cycle. Also, the temperature is restricted to below 210°F ( 99 °C) during the reaction. The mixture is agitated until the reaction is complete, and water may be added for final correction of the desired overall reaction mixture weight. Preferably, air is substantially continuously forcibly dispersed through the reaction mixture during the reaction cycle. Preferably, simultaneously with the injection of the liquid humic substances-aqua mixture and the phosphoric acid, or immediately subsequent thereto, a chelated humic acid is introduced into the reaction mixture. It has been surprisingly discovered that the chelated humic acid serves to prevent the formation of crystals in the reaction product during prolonged storage. In the present example, approximately 1.25 % by weight of chelated humic substance is added. EXAMPLE 4. PROCESS OF PREPARING POTASSIUM AMMONIUM PHOSPHATE LIQUIDS INCORPORATING HUMIC ACID SUBSTANCES. The process of this example produces a liquid composition having a predetermined nitrogen to phosphorous to potassium ratio and further incorporating humic acids. The resulting compositions are safe and available to plants to which applied, and have little tendency to separate during prolonged storage. Concentrations of at least as high as 10% by weight of humic acids can be obtained in the resulting compositions. For illustrative purposes, the present example describes the use of the process in producing a 2,000 pound volume of a composition having a nitrogen to phosphate to potassium analysis of 9:18:9. In the pro.cess as illustrated in this example, a volume of water representing approximately 12^6 % by weight (252 pounds) of the overall reaction mixture is introduced into a suitable reaction vessel. Next, 70% strength phosphoric acid comprising about 25.7% by weight (514 pounds) of the final product volume is introduced substantially simultaneously with about 21.45% by weight (429 pounds) of 42% strength potassium hydroxide into the water. The pH of the mixture is monitored and maintained in a range of from about 6.5 to 7.0. Aqua or ammonia, constituting approximately 22.0% by weight (440 pounds) of the reaction product volume is separately pre-mixed with about 7.0 % by weight (140 pounds) of an organic acid which preferably, although not necessarily, is a humic acid fraction. The volume of humic acid used can represent anywhere from about 3 to about 10 % of the total product volume in various products produced by this process. The premixed aqua (or ammonia) and organic acid is then introduced to the reaction medium. As in the preceding example, preferably simultaneously with the introduction of the liquid humic substance mixture into the reaction vessel, or immediately subsequent thereto, a chelated hurac acid is introduced into the reaction mixture. In the present example, the chelated humic substance totals approx¬ imately 1.25 % (25 pounds) of the reaction product weight. Optionally, the liquid humic or organic acid can be pre-mixed with the potassium hydroxide and introduced together with it. Also, a portion of the liquid humic acid can be pre-mixed with the potassium hydroxide, with the balance being pre-mixed with the aqua or ammonia. During the reaction cycle, the mixture is circulated and maintained at a pH in the range of from about 6.8 to about 7.5. The temperature is kept below 210°F (99°C)and preferably below 205°F (96 °C) . Also, as in the preceding examples, it is preferable that air be forcibly dispersed through the reaction medium during the entire reaction cycle. Approximately 10.0% by weight (200 pounds) of dry urea is added at the end of the reaction cycle to bring the total nitrogen level to the desired level. While the compositions and processes disclosed herein are described in terms of particular ingredients and ranges thereof, it is understood that modifications and variations in the nature and proportions of the ingredients may be made without departing from the spirit and scope of the invention, which is not to be limited to the illustrative details disclosed.

Claims: What is claimed is: 1. A process of preparing a liquid plant nutrient composition comprising reacting in an aqueous medium a predetermined quantity of phosphoric acid with a predetermined volume of a liquid selected from the group consisting of aqua and an aqueous solution of ammonia; and maintaining the temperature of the reaction medium below about 210°F (99°C) during the reaction. 2. The process of claim 1 wherein the pH of the combined reactants during the reaction cycle is maintained in the range of from about 6 to about 8. 3. The process of claim 2 wherein the temperature • of the reaction medium is maintained at a temperature no greater than 205°F (96°C) during the entire reaction. 4. A process of preparing a liquid plant nutrient composition comprising introducing a predetermined volume of water into a reaction vessel to constitute a reaction medium; introducing a predetermined volume of phosphoric acid into the reaction vessel; introducing a predetermined volume of potassium hydroxide into the reaction vessel for reaction with the phosphoric acid ; introducing a predetermined volume of a liquid selected from the group consisting of ammonia and aqua into the reaction vessel for reaction with the phosphoric acid and potassium hydroxide; and maintaining the tempera- ture of the reaction medium during the reaction below about 210°F (99°C). - 5. The process of claim 4 further comprising adjusting the pH of the reaction medium subsequent to the introduction of potassium hydroxide and phosphoric acid in a range from about 6.5 to about 7.5. 6. The process of claim 5 further comprising introducing urea into the reaction vessel subsequent to the introduction of the liquid selected from the group consisting of ammonia and aqua. 7. A process of preparing a liquid plant nutrient composition comprising introducing a predetermined volume of water into a reaction vessel to provide an aqueous reaction medium; mixing a predetermined volume of an organic acid and a predetermined volume of a liquid selected from the group consisting of aqua and ammonia; introducing the pre-mixed organic acid and liquid into the reaction medium substantially simultan- eously. with a predetermined volume of phosphoric acid for reaction thereamong; and maintaining the temperature of the reaction medium at a temperature no greater than about 210°F (99°C) during the reaction. 8. The process of claim 7 further comprising maintaining the pH of the reaction medium in the range of from about 6.5 to about 7.5 during the reaction. 9. The process of claim 8 further comprising forcing air through the reaction medium during the reaction. 10. A process of preparing a liquid plant nutrient composition comprising introducing a predetermined volume of water into a reaction vessel to provide an aqueous reaction medium; pre-mixing a predetermined volume of a liquid selected f rom the group consisting of aqua and ammonia with a liquid mixture of humic acids; introducing the pre-mixed liquids into the water substantially simul taneously with a predetermined volume of phosphoric acid; and introducing a predetermined volume of an aqueous mixture of chelated humic acids into the reaction medium. 11. The process of claim 10 further comprising maintaining the reaction medium at a temperature no greater than 210°F (99°C) during the reaction. 12. The process of claim 11 wherein the pH of the reaction medium is maintained in a range of from about 7 to about 7.5 during the reaction. 13. The process of claim 12 further comprising forcing air through the reaction medium during the reaction. 14. A process of preparing a liquid plant nutrient composition comprising pre-mixing a predetermined volume of a liquid selected from the group consisting of ammonia and aqua with a predetermined volume of a liquid organic acid mixture; introducing a predetermined volume of water into a reaction vessel to provide a reaction medium; introducing a predetermined volume of phosphoric acid and a predetermined volume of potassium hydroxide into the reaction medium; introducing the pre-mixed liquids into the reaction medium; and introducing a predetermined volume of a liquid mixture of chelated humic acids into the reaction medium. 15. The process of claim 14 further comprising maintaining the reaction medium at a pH in the range of about 6.8 to about 7.5; and maintaining the reaction medium at a temperature no greater than about 210 °F (99°C) . 16. A process of preparing a liquid plant nutrient composition comprising pre-mixing a predetermined volume of a liquid selected from the group consisting of aqua and ammonia with a liquid mixture of humic acids to provide a first reactant mixture; pre-mixing a predetermined volume of humic acids with a predeterm¬ ined volume of potassium hydroxide to provide a second reactant mixture; introducing a volume of water into a reaction vessel to provide a reaction medium; introducing the second reactant mixture into the reaction medium with a predetermined volume of phosphoric acid; introducing the first reactant mixture into the reaction medium; introducing a volume of chelated humic acids into the reaction medium; and maintaining the temperature of the reaction medium below about 210°F (99°C) . 17. The process of " claim 16 further comprising maintaining the pH of the reaction medium in a range of from about 6.8 to about 7.5. 18. The process of claim 17 further comprising passing air through the reaction medium. 19. A composition produced in accordance with the process of any one of the preceding claims.

Inventors: MARIHART JOHN R, MARIHART, JOHN, R.
Applicants: PACIFIC MICRO MINERALS INC, PACIFIC MICRO MINERALS, INC.
Application year: 1985
Main classification: C05B7
IPC codes: C05B7