Inorganic phosphorus fertilizer

Concentrated phosphorus fertilizers of the phosphorous variety are described which are absorbed quickly into plant systems and improve plant growth. Particularly described are fertilizers having a combination of phosphorous acid or its salts thereof, and either (a) polyphosphoric acid and its salts thereof; or (b) phosphoric acid and its salts thereof. This combination phosphorus fertilizer, when combined within a specific ratio range, increases phosphorus uptake to plants thereby enhancing plant growth.

BACKGROUND 
 This invention relates to phosphorus fertilizers and their method of 
 preparation. In particular, this invention relates to a fertilizer having 
 a combination of phosphorous acid or its salts thereof, and either (a) 
 polyphosphoric acid and its salts thereof; or (b) phosphoric acid and its 
 salts thereof. This combination phosphorus fertilizer, when combined 
 within a specific ratio range, reduces the risk of formation of phosphorus
 or calcium phosphate precipitates. It further increases the phosphorus 
 uptake to plants and thereafter can be oxidized into a form more readily 
 useable by a plant system. 
 Fertilizers have long been used to supply needed nutrition to plants. The 
 principle components of plant fertilizers have centered on three elements:
 nitrogen, phosphorus and potassium. 
 Phosphorus is not found in nature in its elemental form. The principal 
 source of phosphorus for the fertilizer industry, however, is obtained 
 from the ores of phosphorus containing minerals. The usual practice in the
 fertilizer industry is to convert phosphorus ores into a phosphorus 
 product containing the phosphoric radical (PO.sub.4.sup.-3) which can be 
 absorbed, although rather inefficiently, into plants and thereafter used 
 as nutrition. It is well known in the prior art that phosphorus is 
 biologically active and nutritionally useful to plants only in the 
 phosphoric form (PO.sub.4.sup.-3). A common source of the phosphoric 
 radical (PO.sub.4.sup.-3) for fertilizers is phosphoric acid. 
 Many of the phosphorus fertilizers currently used have a number of 
 undesired qualities. First, if prepared in concentrated solutions, they 
 tend to form undesired precipitates in a short period of time. Further, 
 these concentrated solutions must be maintained within a narrow pH range 
 to prevent precipitation, which results in fertilizers with limited 
 application. Precipitates are undesirable since they can not be absorbed 
 by plants. 
 Still another problem with phosphorus containing fertilizers, particularly 
 phosphoric fertilizers, is that they are not readily absorbed by foliage 
 and must be applied to the soil and thereafter absorbed by the plant root 
 system. Since only a small portion of the phosphoric fertilizer applied to
 the soil is actually absorbed by a root system, frequent reapplication 
 usually occurs. This is undesirable because it can lead to leaching of 
 phosphate into the groundwater which may cause eutrophication of lakes, 
 ponds and streams. 
 Prior art formulas of phosphorus fertilizers have identified these 
 problems. U.S. Pat. No. 5,514,200, issued to Lovatt, describes a formula 
 utilizing the more readily absorbed phosphorous form (PO.sub.3.sup.-3) in 
 a composition buffered with an organic acid. However, as is discussed 
 below, the present invention represents an improved and more effective 
 composition for providing phosphorus to plants. 
 SUMMARY 
 The present invention is directed to a concentrated phosphorus fertilizer 
 solution which consists essentially of phosphorous acid or its salts 
 dissolved in water and stabilized with an inorganic complexing agent such 
 as polyphosphoric acid to prevent phosphorus or calcium phosphate 
 precipitation. Reduction of the formation of phosphorus or calcium 
 phosphate precipitates, allows the concentrated phosphorus fertilizer to 
 be stored for long periods of time. When subsequently diluted, the 
 fertilizer can be applied to plants and/or soil, being easily absorbed 
 through the foliage or the root system of a plant. The absorbed phosphorus
 is then used by plants to perform or accelerate biological functions which
 are defined here to include plant growth, improved quality, improved 
 disease resistence, and improved vigor. 
 Although the present invention can function properly and remain dissolved 
 in solution in the range of pH between 0.5 and 10.0, it is preferably 
 maintained in a pH range between 5.0 and 7.5 for ideal absorption into 
 plants either by foliar or soil applications. 
 Testing, the results of which are provided below, indicate that phosphorous
 acid or its salts, in combination with either (a) polyphosphoric acid or 
 its salts, or (b) phosphoric acid or its salts, when used as a plant 
 fertilizer, has a synergistic effect which improves plant growth than if 
 phosphorous, polyphosphoric or phosphoric fertilizers were used 
 individually on plant systems. 
 The desired weight ratio of phosphorus derived from phosphorous acid or its
 salts to phosphorus derived from either (a) polyphosphoric acid or its 
 salts, or (b) phosphoric acid or its salts, is between 1:10 to 10:1. 
 However, the range can be from 1:20 to 20:1. Alternatively, (a) and (b) 
 described above may be combined so that the weight ratio to phosphorous 
 acid or its salts is between 1:20 to 20:1. 
 Other features and advantages will become apparent to those skilled in the 
 art upon review of the following detailed description and claims. 
 DESCRIPTION 
 A phosphorus fertilizer is prepared by mixing phosphorous acid or its salts
 with either: phosphoric acid or its salts; or, polyphosphoric acid or its 
 salts. The phosphorus derived from phosphoric acid or its salts or 
 polyphosphoric acid or its salts is designated as PO.sub.4.sup.-3 and 
 phosphorus derived from phosphorous acid or its salts is designated as 
 PO.sub.3.sup.-3. The ratio of PO.sub.4.sup.-3 to PO.sub.3.sup.-3 in the 
 prepared phosphorus fertilizer ranges from 1:20 to 20:1. Mixing of 
 PO.sub.4.sup.-3 with PO.sub.3.sup.-3 produces a synergistic effect of 
 PO.sub.4.sup.-3 and PO.sub.3.sup.-3 on plant growth and uptake of 
 phosphorus by plants. 
 Mixing of PO.sub.4.sup.-3 and PO.sub.3.sup.-3 also enables the preparation 
 of high phosphorus liquid fertilizers with better stability and little, if
 any precipitation. However, although liquid preparations are more 
 desirable, dry preparations are also possible. 
 To prepare the fertilizer of the present invention, phosphorous acid or its
 salts, PO.sub.3.sup.-3 are dissolved in water. The solution is then 
 stabilized by adding PO.sub.4.sup.-3, added in intervals, until the 
 PO.sub.4.sup.-3 constitutes within the range 1:20 to 20:1 by weight 
 relative to the amount of PO.sub.3.sup.-3 present. 
 The novel composition can be delivered to plants by foliar or soil 
 applications such as through an irrigation system. The phosphorus 
 fertilizers so prepared are taken up by plants in the phosphorous form and
 are gradually converted by enzymes in the plants to phosphoric form to 
 perform or accelerate biological functions in the plant. 
 Phosphorous acid is a genus which includes the following species: 
 phosphorous acid, hypophosphorous acid, polyphosphorous acid, 
 polyhypophosphorous acid. 
 Salts of phosphorous acid contemplated by this invention include but are 
 not limited to ammonium phosphite, calcium phosphite, magnesium phosphite,
 manganese phosphite, potassium phosphite, sodium phosphite, and zinc 
 phosphite. 
 Phosphoric acid exists in the meta (HPO.sub.3), pyro (H.sub.4 P.sub.2 
 O.sub.7) and ortho (H.sub.3 PO.sub.4) form. 
 Salts of phosphoric acid contemplated by this invention include but are not
 limited to ammonium phosphate, calcium phosphate, ferrous phosphate, 
 aluminum phosphate, ferric phosphate, magnesium phosphate, manganese 
 phosphate, sodium phosphate, and zinc phosphate. 
 Polyphosphoric acid is a genus which includes the following species: 
 polyphosphoric acid, dipolyphosphoric acid, tripolyphosphoric acid, tetra 
 polyphosphoric acid, penta polyphosphoric acid, hexapolyphosphoric acid or
 combinations thereof. 
 Salts of polyphosphoric acid include but are not limited to potassium 
 polyphosphate, ammonium polyphosphate, sodium polyphosphate, zinc 
 polyphosphate, magnesium polyphosphate and iron polyphosphate. 
 The desired pH range is between 5.0 and 7.5. However, the pH can be from 
 0.5 to 10.0. 
 In order to more clearly define the invention, the following examples of 
 methods of preparation are set forth. These examples are illustrative only
 and are not limiting as to the scope of the invention. 
 Examples I and VII are typical fertilizer found in the prior art. Examples 
 II and VIII embody the present invention with regards to phosphorous acid 
 and an inorganic complexing agent. Examples III and IX are also prior art 
 formulations embodying formulations of the Lovatt U.S. Pat. No. 5,514,200 
 which utilize phosphorous acid buffered with an organic acid. Examples IV,
 V and VI set forth alternative compositions of matter embodying the 
 concept of the present invention. 
 Examples X, XI, XIII, XV, XVI, XIX, XX and XXI are typical of fertilizers 
 found in the prior art. Examples XII, XIV, XVII, XVIII, XXII, and XXIII 
 are also embodiments of the present invention.

EXAMPLE I (PRIOR ART) 
 A 0-28-25 fertilizer was prepared by mixing the following: 
 (1) 376 grams water 
 (2) 299 grams potassium hydroxide 
 (3) 325 grams phosphorous acid 
 The fertilizer had a pH of approximately 6.2 with a resulting appearance 
 that was cloudy. The solution was analyzed to contain 25.9% P.sub.2 
 O.sub.5 and 25.2% K.sub.2 O. 
 EXAMPLE II 
 A 0-28-25 fertilizer was prepared by mixing the following: 
 (1) 366 grams water 
 (2) 299 grams potassium hydroxide 
 (3) 315 grams phosphorous acid 
 (4) 10 grams polyphosphoric acid 
 The fertilizer had a pH of approximately 6.2 with a resulting appearance 
 that was clear and was analyzed to contain 28.1% P.sub.2 O.sub.5 and 24.9%
 K.sub.2 O. 
 EXAMPLE III (U.S. Pat. No. 5,514,200) 
 A 0-28-25 fertilizer was prepared by mixing the following: 
 (1) 356 grams water 
 (2) 299 grams potassium hydroxide 
 (3) 325 grams phosphorous acid 
 (4) 20 grams citric acid 
 The resulting appearance was clear with some precipitation. The solution 
 was analyzed to contain 26.2% P.sub.2 O.sub.5 and 24.7% K.sub.2 O. 
 In comparing Examples I, II, and III, the results indicate that the 
 composition embodying the invention, Example II, results in over 10% 
 additional P.sub.2 O.sub.5 in solution than either the prior art or the 
 recent patented formulation according to Lovatt. 
 Experiment 1 
 The 3 fertilizer samples prepared as Examples I, II, and III were diluted 
 with water at a ratio of concentrate to water of 1:250. The solutions were
 then sprayed on tomato plants at 5 mililiters per each plant. Four 
 different plants were sprayed with each solution. One week after the 
 application of the solution, the twelve plants were cut at soil level, 
 washed with dilute acid and water and then dried in an oven at 75.degree. 
 C. for 24 hours. The dried plants were then analyzed for total phosphorus 
 and potassium. The analysis results are as follows: 
 DRIED PLANT ANALYSIS 
 
 Example I Example II Example III 
 Prior art invention Lovatt patent 
 Total P (%) 0.69 0.82 0.69 
 Total K (%) 1.90 1.91 1.79 
 The results of Experiment 1 indicate that the composition of Example II 
 provides an improved rate of absorption of phosphorus into a plant 18.18% 
 better when compared with the prior art or a comparable formula as taught 
 by Lovatt without affecting the potassium uptake. 
 Experiment 2 
 Experiment 1 was repeated upon bush bean plants rather than tomato plants. 
 The analysis results are as follows: 
 DRIED PLANT ANALYSIS 
 
 Example I Example II Example III 
 Prior art Invention Lovatt patent 
 Total P (%) 0.26 0.31 0.27 
 Total K (%) 1.73 1.80 1.78 
 The results indicate that the novel composition of Example II provides an 
 improved rate of absorption of phosphorus (19.2% improvement) into a bush 
 bean plant when compared to the prior art or a comparable formula 
 according to Lovatt (4% improvement). 
 EXAMPLE IV 
 A 4-25-15 fertilizer was prepared by mixing the following: 
 (1) 438 grams water 
 (2) 180 grams potassium hydroxide 
 (3) 285 grams phosphorous acid 
 (4) 87 grams urea 
 (5) After all the materials were dissolved, 10 grams of ammonium 
 polyphosphate was added. 
 The resulting fertilizer had a pH of 5.9 and analyzed to obtain 4.1% N, 
 25.2% P.sub.2 O.sub.5 and 14.9% K.sub.2 O. 
 EXAMPLE V 
 A 0-40-0 fertilizer was prepared by mixing the following: 
 (1) 534 grams water 
 (2) 463 grams phosphorous acid 
 (3) 3 grams tripolyphosphate 
 The fertilizer had a pH of 0.5 and was clear in appearance. This fertilizer
 can be further diluted with water at ratios of concentrate to water up to 
 1:10,000 and used as soil application or with irrigation water. 
 EXAMPLE VI 
 A 0-27-25 fertilizer was prepared by mixing the following: 
 (1) 308 grams water 
 (2) 307 grams phosphorous acid 
 (3) 365 potassium carbonate 
 (4) 20 grams potassium polyphosphate 
 The pH was approximately 6.2 and the fertilizer was observed to remain in 
 solution for 30 days without formation of precipitate. 
 EXAMPLE VII (PRIOR ART) 
 A 4-25-15 fertilizer was prepared by mixing the following: 
 (1) 448 grams water 
 (2) 180 grams potassium hydroxide 
 (3) 285 grams phosphorous acid 
 (4) 87 grams urea 
 The fertilizer had a pH of approximately 5.8 and was analyzed to contain 
 4.1% N, 24.8% P.sub.2 O.sub.5 and 15.3% K.sub.2 O. 
 EXAMPLE VIII 
 A 4-25-15 fertilizer was prepared by mixing the following: 
 (1) 448 grams water 
 (2) 180 grams potassium hydroxide 
 (3) 275 grams phosphorous acid 
 (4) 87 grams urea 
 (5) 10 grams polyphosphoric acid 
 The fertilizer had a pH of approximately 5.9 and was analyzed to contain 
 4.1% N, 25.2% P.sub.2 O.sub.5 and 15.1% K.sub.2 O. 
 EXAMPLE IX (U.S. Pat. No. 5,514,200) 
 A 4-25-15 fertilizer was prepared by mixing the following: 
 (1) 428 grams water 
 (2) 180 grams potassium hydroxide 
 (3) 285 grams phosphorous acid 
 (4) 87 grams urea 
 (5) 20 grams citric acid 
 The fertilizer had a pH of approximately 5.1 and was analyzed to contain 
 4.1% N, 24.6% P.sub.2 O.sub.5 and 15.0% K.sub.2 O. 
 Experiment 3 
 Samples from Examples VII, VIII, and IX were diluted 250 to 1 with water 
 and then sprayed on tomato plants at 5 milliliters per plant. Four 
 different plants were sprayed with each solution. One week after the 
 application of the solution, the twelve plants were cut at soil level, 
 washed with dilute acid and water and then dried in an oven at 75 degrees 
 C for 24 hours. The dried plants were then analyzed for nitrogen, 
 phosphorus and potassium. The analysis results are as follows: 
 DRIED PLANT ANALYSIS 
 
 Example VII Example VIII Example IX 
 Prior art Invention Lovatt patent 
 Total N (%) 3.9 3.9 3.6 
 Total P (%) 0.41 0.49 0.40 
 Total K (%) 2.82 2.95 2.93 
 As in Experiments 1 and 2, the fertilizer embodying the invention increased
 the plant's phosphorus intake by about 20% when compared to examples of 
 the prior art. 
 EXAMPLE X (PRIOR ART) 
 A 0-40-0 fertilizer was prepared by mixing the following: 
 (1) 535 grams water 
 (2) 465 grams phosphorous acid 
 EXAMPLE XI (PRIOR ART) 
 A 0-40-0 fertilizer was prepared by mixing the following: 
 (1) 518 grams water 
 (2) 482 grams polyphosphoric acid 
 EXAMPLE XII 
 A 0-40-0 fertilizer was prepared by mixing the following: 
 (1) 526.5 grams water 
 (2) 232.5 grams phosphorous acid 
 (3) 241 grams polyphosphoric acid 
 EXAMPLE XIII (PRIOR ART) 
 A 0-40-0 fertilizer was prepared by mixing the following: 
 (1) 444 grams water 
 (2) 556 grams phosphoric acid 
 EXAMPLE XIV 
 A 0-40-0 fertilizer was prepared by mixing the following: 
 (1) 489.5 grams water 
 (2) 232.5 grams phosphorous acid 
 (3) 278 grams phosphoric acid 
 In concentrated form, the fertilizer described in either Example III or V 
 had a pH of 0.5 and was clear in appearance. Further, the fertilizers 
 described in either Example III or V can be further diluted with water at 
 ratios of concentrate to water up to 1:10,000 and used as soil 
 application, with irrigation water or directly applied to the plant 
 foilage. 
 Experiment 4--Dried Plant Analysis 
 The five fertilizer samples prepared as Examples X through XIV were diluted
 with water at a ratio of concentrate to water of 1:10,000. Each fertilizer
 solution was then applied as drench to separate pots each containing one 
 tomato plant standing from 15-20 centimeters in height. Four plants were 
 treated with each solution. Each plant received 500 milliliters of 
 solution. Four plants were also used as a reference and received no 
 fertilizer. Each pot also received 250 milliliters of water, twice per 
 day. Each plant received its respective solution (500 ml) 5 separate times
 with 2 day intervals between each application. Forty five days after the 
 first application of the solutions, the plants were cut at soil level, 
 washed with dilute acid and distilled water and then dried in an oven at 
 75.degree. C. for 24 hours. The dried plants were then weighted for dry 
 matter and then analyzed for total phosphorus. The analysis results are as
 follows: 
 EXPERIMENT 4--DRIED PLANT ANALYSIS 
 
 Ex. X Ex. XI Ex. XIII 
 Prior Prior Prior Ex. Water 
 art art Ex. XII art XIV Only 
 Dry Matter 21.6 22.9 25.1 23.2 26.4 20.8 
 (g/plant) 
 Total P (%) 0.42 0.43 0.45 0.45 0.48 0.35 
 Total P .091 .098 .113 .104 .127 .073 
 (g/plant) 
 The novel fertilizer solution of Example XII contains phosphorus 
 fertilizers present in Examples X and XI. The combination of 
 polyphosphoric acid and phosphorous acid of Example XII showed a 24.2% 
 increase in the percent of phosphorus uptake and a 16.2% increase in dry 
 matter over Example X. Similarly, Example XII showed a 15.3% increase in 
 the percent of phosphorus uptake and a 9.6% increase in dry matter over 
 Example XI. 
 The novel fertilizer solution of Example XIV contains phosphorus 
 fertilizers present in Examples X and XIII. The combination of phosphoric 
 acid and phosphorous acid of Example XIV showed a 40.0% increase in the 
 percent of phosphorus uptake and a 22.2% increase in dry matter over 
 Example X. Similarly, Example XIV showed a 22.1% increase in the percent 
 of phosphorus uptake and a 13.8% increase in dry matter over Example XIII.
 The test results indicate improved phosphorus uptake and increased plant 
 mass by use of a combination phosphorus fertilizer; particularly the 
 phosphorous acid/phosphoric acid combination of Example XIV. 
 EXAMPLE XV (PRIOR ART) 
 A 0-15-14 fertilizer having a pH of 6.7 was prepared by mixing the 
 following: 
 (1) 657 grams water 
 (2) 175 grams phosphorous acid 
 (3) 168 potassium hydroxide 
 EXAMPLE XVI (PRIOR ART) 
 A 0-15-14 fertilizer having a pH of 6.3 was prepared by mixing the 
 following: 
 (1) 623 grams water 
 (2) 209 grams phosphoric acid 
 (3) 168 grams potassium hydroxide 
 EXAMPLE XVII 
 A 0-15-14 fertilizer having a pH of 6.5 was prepared by mixing the 
 following: 
 (1) 640 grams water 
 (2) 87.5 grams phosphorous acid 
 (3) 104.5 grams phosphoric acid 
 (4) 168 grams potassium hydroxide 
 EXAMPLE XVIII 
 A 0-15-14 fertilizer having a pH of 6.5 was prepared by mixing the 
 following: 
 (1) 640 grams water 
 (2) 83 grams phosphorous acid 
 (3) 99 grams phosphoric acid 
 (4) 10 grams polyphosphoric acid 
 (5) 168 grams potassium hydroxide 
 Experiment 5--Stability Test 
 Examples XV, XVI, XVII and XVIII were analyzed immediately after 
 preparation. The results are shown in the following table. After the 
 initial analysis, the samples were placed in containers and tightly 
 covered with lids. After standing at room temperature for 48 hours, each 
 sample was first visually observed for the presence of precipitates and 
 thereafter filtered. The filtrates from each sample were analyzed for 
 total phosphorus and potassium. The observations and analysis results are 
 as follows: 
 EXPERIMENT 5--STABILITY TEST RESULTS 
 
 Ex. XV Ex. XVI Ex. Ex. 
 Prior Art Prior Art XVII XVIII 
 Analysis Results 
 at Preparation 
 P.sub.2 O.sub.5 (%) 15.2 14.9 15.1 15.0 
 K.sub.2 O (%) 14.0 13.7 14.3 14.1 
 Appearance after 48 hours Clear Precipitation Clear Clear 
 Analysis Results 
 after 48 hours 
 P.sub.2 O.sub.5 (%) 15.1 12.1 15.2 15.0 
 K.sub.2 O (%) 14.0 12.7 14.2 14.0 
 The test results indicate that the novel phosphorus combination of Examples
 XVII and XVIII maintain phosphorus and potassium in solution. Also 
 apparent is that phosphoric acid, when used in combination with 
 phosphorous acid as in Example XVII, or when used in combination with 
 phosphorous acid and polyphosphoric acid as in Example XVIII, remain in 
 solution and do not form precipitates as indicated for Example XVI. 
 EXAMPLE XIX (PRIOR ART) 
 A 0-12-11 fertilizer having a pH of 6.4 was prepared by mixing the 
 following: 
 (1) 728 grams water 
 (2) 140 grams phosphorous acid 
 (3) 132 grams potassium hydroxide 
 EXAMPLE XX (PRIOR ART) 
 A 0-12-11 fertilizer having a pH of 6.2 was prepared by mixing the 
 following: 
 (1) 701 grams water 
 (2) 167 grams phosphoric acid 
 (3) 132 grams potassium hydroxide 
 EXAMPLE XXI (PRIOR ART) 
 A 0-12-11 fertilizer having a pH of 6.2 was prepared by mixing the 
 following: 
 (1) 723 grams water 
 (2) 145 grams polyphosphoric acid 
 (3) 132 grams potassium hydroxide 
 EXAMPLE XXII 
 A 0-12-11 fertilizer having a pH of 6.3 was prepared by mixing the 
 following: 
 (1) 714.5 grams water 
 (2) 70 grams phosphorous acid 
 (3) 83.5 grams phosphoric acid 
 (4) 132 grams potassium hydroxide 
 EXAMPLE XXIII 
 A 0-12-11 fertilizer having a pH of 6.3 was prepared by mixing the 
 following: 
 (1) 725.5 grams water 
 (2) 70 grams phosphorous acid 
 (3) 72.5 grams polyphosphoric acid 
 (4) 132 grams potassium hydroxide 
 Experiment 6--Foliar Application Test (7-Day) 
 The following is a tabular presentation of the fertilizers described in 
 Examples XIX through XXIII: 
 Composition of Fertilizers in Examples XIX-XXIII: 
 (all values in grams) 
 
 Ex. XIX Ex. XX Ex. XXI Ex. Ex. 
 Prior Art Prior Art Prior Art XXII XXIII 
 Water 728 701 723 714.5 725.5 
 Potassium 132 132 132 132 132 
 hydroxide 
 Phosphorous acid 140 -- -- 70 70 
 Phosphoric acid -- 167 -- 83.5 -- 
 Polyphosphoric -- -- 145 -- 72.5 
 acid 
 Fertilizer samples XIX through XXIII were each diluted with 250 times of 
 water. The solutions were then sprayed onto tomato plants at 10 
 milliliters per plant. Each tomato plant had a height of between 15-20 
 centimeters prior to receiving the first application of solution. Eight 
 plants were sprayed with each solution and also received 250 milliliters 
 of water, twice daily. One week after the application of the solution, 
 four plants from each treatment were cut at soil level, washed with dilute
 acid and distilled water and then dried in an oven at 75 degrees C for 24 
 hours. The dried plants were then analyzed for total phosphorus and 
 potassium. The results are as follows: 
 EXPERIMENT 6--DRIED PLANT ANALYSIS (7-Day) 
 
 Ex. XIX Ex. XX Ex. XXI Ex. Ex. No 
 Prior art Prior art Prior art XXII XXIII Spray 
 Dry Matter 5.88 6.86 5.94 6.89 6.25 6.17 
 (g/plant) 
 Total P (%) 0.48 0.45 0.41 0.52 0.49 0.38 
 Total K (%) 1.86 1.79 1.72 1.82 1.75 1.69 
 Fertilizer examples XIX, XXII and XXIII contain phosphorous acid. 
 The combination of polyphosphoric acid and phosphorous acid in Example 
 XXIII showed a 2.1% increase in the percent of phosphorus uptake and a 
 6.3% increase in dry matter over Example XIX. 
 The combination of phosphoric acid and phosphorous acid in Example XXII 
 showed a 8.3% increase in the percent of phosphorus uptake and a 17.2% 
 increase in dry matter over Example XIX. Fertilizer examples XX and XXII 
 contain phosphoric acid. 
 The combination of phosphoric acid and phosphorous acid in Example XXII 
 showed a 15.6% increase in the percent of phosphorus uptake and a 0.4% 
 increase in dry matter over Example XX. Fertilizer examples XXI and XXIII 
 have polyphosphoric acid. 
 The combination of polyphosphoric acid and phosphorous acid in Example 
 XXIII showed a 19.5% increase in the percent of phosphorus uptake and a 
 5.2% increase in dry matter over Example XXI. 
 Experiment 7 Foliar Application Test (45-Day) 
 The remaining four uncut plants from each treatment (Experiment 6) were 
 kept in a greenhouse for a total of 45 days from the date of the first 
 application of the solution. Each plant was watered twice per day (250 
 milliliters). At that time, they were cut at soil level, washed with 
 dilute acid and distilled water and then dried in an oven at 75C for 24 
 hours. The dried plants were weighed for dry matter yields and then 
 analyzed for total phosphorus and potassium. The dry matter yields and 
 analysis are shown below: 
 EXPERIMENT 7--DRIED PLANT ANALYSIS (45-Day) 
 
 Ex. XIX Ex. XX Ex. XXI Ex. Ex. No 
 Prior art Prior art Prior art XXII XXIII Spray 
 Dry Matter 26.7 2.84 27.9 31.7 30.2 25.3 
 (g/plant) 
 Total P (%) 0.38 0.41 0.36 0.45 0.40 0.36 
 Total P 0.101 0.116 0.100 0.143 0.121 0.091 
 (g/plant) 
 Total K (%) 1.91 1.83 1.93 1.85 2.02 2.03 
 Total K 0.510 0.520 0.538 0.586 0.610 0.510 
 (g/plant) 
 As in experiment 6, the prior art fertilizers of example XIX and XX will be
 compared to example XXII and the prior art fertilizers of example XIX and 
 XXI will be compared to example XXIII. 
 The combination of polyphosphoric acid and phosphorous acid in Example 
 XXIII showed a 19.8% increase in phosphorus uptake and a 13.1% increase in
 dry matter over Example XIX. 
 The combination of phosphoric acid and phosphorous acid in Example XXII 
 showed a 41.6% increase in phosphorus uptake and a 18.7% increase in dry 
 matter over Example XIX. 
 The combination of phosphoric acid and phosphorous acid in Example XXII 
 showed a 23.3% increase in phosphorus uptake and a 11.6% increase in dry 
 matter over Example XX. 
 The combination of polyphosphoric acid and phosphorous acid in Example 
 XXIII showed a 21.0% increase in phosphorus uptake and a 8.2% increase in 
 dry matter over Example XXI. 
 The results indicate that combinations of phosphorous acid with either 
 phosphoric acid or polyphosphoric acid can enhance the uptake of 
 phosphorus by plants. The test results also indicate that there is a 
 synergistic effect by the combination of phosphorous acid with either 
 phosphoric acid or phosphorous acid on plant growth.