NOVEL PHOSPHATIC FERTILIZERS BASED ON ALKANOLAMINE SALTS OF PHOSPHORIC ACID

Abstract

The invention relates to use of alkanolamine salts of phosphoric acid as an ammonium-free fertilizer. The invention also discloses aqueous compositions, comprising an alkanolamine salt of phosphoric acid and at least an alkanolamine metal complex.

Claims

1. Use of alkanolamine salts of phosphoric acid as an ammonium-free fertilizer.

2. Use according to claim 1, wherein the alkanolamine is selected from the group of mono-, di- and tri-ethanolamine, mono-, di- and tri-isopropanolamine, and mixtures thereof.

3. Use according to any one of claims 1 to 2, wherein the alkanolamine is mono-ethanolamine.

4. Use according to any one of claims 1 to 3, wherein the fertilizer is an aqueous fertilizer solution.

5. Use according to claim 4, wherein the P.sub.2O.sub.5 content of the aqueous fertilizer solution ranges from 5 to 40 weight % (w/w), relative to the total weight of the fertilizer.

6. Use according to any one of claims 2 to 5, wherein the molar ratio of phosphoric acid and mono-ethanolamine is between 3:1 and 1:3, more preferably 2:1 and 1:2.5, most preferably between 1:1 and 1:2.

7. Use according to any one of claims 4 to 6, wherein the aqueous fertiliser solution is applied by spraying onto the soil, injecting into the soil, banding, incorporation into the seedbed during drilling, via fertigation or hydroponics systems, by foliar application, or by seed coating.

8. Aqueous composition, comprising an alkanolamine salt of phosphoric acid and at least an alkanolamine metal complex.

9. Aqueous composition according to claim 8, wherein the alkanolamine of the alkanolamine metal complex is mono-ethanolamine.

10. Aqueous composition according to claim 9, wherein the molar ratio of phosphoric acid and mono-ethanolamine of the mono-ethanolamine salt of phosphoric acid is between 3:1 and 1:3, more preferably 2:1 and 1:2.5, most preferably between 1:1 and 1:2.

11. Aqueous composition according to any one of claims 8 to 10, wherein the P.sub.2O.sub.5 content of the composition ranges from 5 to 40 weight % (w/w), relative to the total weight of the aqueous composition.

12. Aqueous composition according to any one of claims 8 to 11, wherein the alkanolamine metal complex is selected from the group of boron ethanolamine, copper ethanolamine, zinc ethanolamine and iron ethanolamine.

13. Aqueous composition according to any one of claims 8 to 12, further comprising an ammonium-free nitrogen source and/or a potassium source.

14. Aqueous composition according to any one of claims 8 to 13, wherein the nitrogen source is urea or a nitrate compound, and/or the potassium source is potassium nitrate or potassium sulphate.

15. Aqueous composition according to any one of claims 8 to 14, further comprising one or more elements, selected from the group of calcium, magnesium, sulphur, sodium, boron, copper, iron, manganese, molybdenum and zinc.

16. Aqueous composition according to any one of claims 8 to 15 for use as a fertilizer.

Description

EXPERIMENTAL

Example 1: Phosphatic Fertilizer Containing 34 Weight % P.SUB.2.O.SUB.5

[0032] The following example shows the formulation required to make 1 kg of a liquid phosphatic fertilizer containing 34 weight % P.sub.2O.sub.5, based on a mono-ethanolamine salt of phosphoric acid, produced in the molar ratio of 1 mole of mono-ethanolamine to 1 mole of phosphoric acid. The mono-ethanolamine used was a 90 weight % aqueous solution. The phosphoric acid used was a 75 weight % food grade with a P.sub.2O.sub.5 content of 54.3 weight %.

TABLE-US-00002 Phosphoric acid 75% 626.46 g Mono-ethanolamine 90% 325.38 g Water 48.16 g Total 1000.00 g

[0033] The phosphoric acid was placed in a glass vessel fitted with a cooling jacket and impeller stirrer. Mono-ethanolamine was added slowly to the stirred acid, controlling the rate of addition in such a way as to maintain the temperature below 50 C. After completing the mono-ethanolamine addition, stirring was continued whilst the solution was cooled to room temperature. Water was then added to adjust the batch weight to 1000 g. The resultant product was a clear, colourless, slightly viscous solution with the following physiochemical characteristics:

TABLE-US-00003 P.sub.2O.sub.5 content: 34 weight % pH (neat product): 4.3 Crystallization point: <20 C. Density: 1.426 kg/l

[0034] The product remained stable for at least one year at room temperature.

[0035] It should be noted that a more concentrated product can be produced by omitting the water addition, using more concentrated acid and mono-ethanolamine solutions and allowing the heat of reaction to evaporate water from the reaction mixture.

[0036] Glasshouse trials were carried out in order to assess crop safety of the composition described above. The trials were carried out using a radish test crop grown in pots in a sand medium and fed via a nutrient solution. A randomised block design using 4 replicates was employed. The product was applied by foliar spraying at the 5 leaf growth stage using a rate equivalent to 10 kg/ha in 200 litres/ha water (equating to an input of 3.4 kg P.sub.2O.sub.5 per ha). For comparison, treatments delivering the same input of P.sub.2O.sub.5 per ha in the form of ammonium polyphosphate, phosphoric acid, mono-ammonium phosphate, mono-potassium phosphate and potassium pyrophosphate were also carried out. The crop was assessed for symptoms of phytotoxicity seven days after spraying.

[0037] The only treatment showing signs of crop damage (leaf burn) was the one using phosphoric acid. The trial thus demonstrates the safety of the product based on the mono-ethanolamine salt of phosphoric acid.

[0038] Further glasshouse trials were carried out in order to efficacy of the composition described above in comparison with traditional P sources (phosphoric acid and potassium polyphosphate). The trials were carried out using a tomato test crop grown in pots in a mixed sand/calcareous soil medium using 6 replicates. Nutrients were applied via a fertigation system; in each case, 31 mg/l P.sub.2O.sub.5 was delivered on the irrigation water in each different form. The trial was conducted for a period of 6 weeks and the following parameters assessed: number of flowers and fruit set; nutrient status; root fresh and dry matter.

Example 2: Phosphatic Fertilizer Containing 21 Weight % P.SUB.2.O.SUB.5

[0039] The following example shows the formulation required to make 1 kg of a liquid phosphatic fertilizer containing 21 weight % P.sub.2O.sub.5 based on a mono-ethanolamine salt of phosphoric acid reacted in the molar ratio of 2 mole of mono-ethanolamine to 1 mole of phosphoric acid. The mono-ethanolamine used was a 90 weight % aqueous solution. The phosphoric acid used was 75 weight % food grade with a P.sub.2O.sub.5 content of 54.3 weight %.

TABLE-US-00004 Phosphoric acid 75% 391.98 g Mono-ethanolamine 90% 407.20 g Water 200.82 g Total 1000.00 g

[0040] The phosphoric acid was placed in a glass vessel fitted with a cooling jacket and impeller stirrer. Mono-ethanolamine was added slowly to the stirred acid, controlling the rate of addition in such a way as to maintain the temperature below 50 C. After completing the mono-ethanolamine addition, stirring was continued whilst the solution was cooled to room temperature. Water was then added to adjust the batch weight to 1000 g. The resultant product was a clear, slightly yellowish, slightly viscous solution with the following physiochemical characteristics:

TABLE-US-00005 P.sub.2O.sub.5 content: 21 weight % pH (neat product): 8.5 Crystallization point: <10 C. Density: 1.329 kg/l

[0041] The product remained stable for at least one year at room temperature.

Example 3: Phosphatic Fertilizer Containing 100 g/l P.SUB.2.O.SUB.5 .and 100 g/l Boron (B)

[0042] The following example describes the process to make 1 litre of a mixed liquid fertilizer containing the primary plant nutrient phosphorus plus the micronutrient boron. The nutrient content of the final product is 100 g/l P.sub.2O.sub.5 and 100 g/l boron (B). The phosphatic component of the fertilizer is based on a mono-ethanolamine salt of phosphoric acid reacted in the molar ratio 1.779 mole of mono-ethanolamine to 1 mole of phosphoric acid. The mono-ethanolamine used was a 90 weight % aqueous solution. The phosphoric acid used was 75 weight % food grade with a P.sub.2O.sub.5 content of 54.3 weight %. The boron component of the fertilizer is a compound formed by reaction of mono-ethanolamine with boric acid in the mole ratio 1:3 (commonly referred to in the fertilizer industry as boron ethanolamine being a boron-ethanolamine complex).

TABLE-US-00006 Water 92.39 g Boron ethanolamine 902.06 g Mono-ethanolamine 90% 170.25 g Phosphoric acid 75% 184.30 g Total 1349.00 g

[0043] The water and boron ethanolamine were placed in a glass vessel fitted with an impeller stirrer. Mono-ethanolamine was added to the stirred mixture, followed by the phosphoric acid. The reaction was mildly exothermic and after addition of all the reactants, stirring was continued for 30 minutes. Water was then added to adjust the batch volume to 1 litre. The resultant product was a clear, virtually colourless, slightly viscous solution with the following physiochemical characteristics:

TABLE-US-00007 pH (neat product): 8.2 Crystallization point: <5 C. Density: 1.349 kg/l

[0044] The product remained stable at room temperature without any sedimentation for at least one year.

[0045] The same product may also be produced by making the boron ethanolamine component in situ in the same reaction vessel by reacting mono-ethanolamine and boric acid in the required proportions before the phosphate salt is formed.

[0046] Surprisingly, attempts to produce an equivalent fertilizer composition using conventional phosphate sources proved unsuccessful. Using mono-potassium phosphate, di-potassium phosphate, tetrapotassium pyrophosphate, potassium tripolyphosphate, mono-ammonium phosphate, di-ammonium phosphate or ammonium polyphosphate as the P source to achieve the aforementioned nutrient content of 100 g/l P.sub.2O.sub.5 and 100 g/l boron (B) resulted in products that crystallized or formed precipitates or sediments in a short time. This demonstrates the superior compatibility of the phosphatic component based on mono-ethanolamine salts of phosphoric acid which allows flexibility in formulation of complex plant nutrient compositions.

[0047] Glasshouse trials were carried out in order to assess the efficacy of the phosphorus/boron composition described above when foliar sprayed on to a crop. The trials were carried out using a sunflower test crop grown in pots in a sand medium and fed via a nutrient solution (without boron). A randomised block design using 4 replicates was employed. Details of the treatments are listed below: [0048] Treatment 1: NiI (Control) [0049] Treatment 2: 3 l/ha phosphatic fertilizer according to the invention in 2001/ha water applied at 4 leaf stage [0050] Treatment 3: 4.51/ha phosphatic fertilizer according to the invention in 2001/ha water applied at 4 leaf stage [0051] Treatment 4: 3 l/ha phosphatic fertilizer according to the invention in 2001/ha water applied at 4 leaf stage+3 l/ha in 2001/ha water 14 days later

[0052] The crop was harvested 8 weeks after the second foliar application and plant height, fresh plant weight, dry head weight and dry seed weight were measured. The results are shown in the table below:

TABLE-US-00008 Average Average Average Average Plant Fresh Plant Dry Head Dry Seed Treatment Height Std Weight Std Weight Std Weight Std Number (cm) Dev (g) Dev (g) Dev (g) Dev 1 44.50 8.81 74.05 28.05 8.30 2.77 0.08 0.08 2 49.25 10.66 233.64 52.45 28.67 3.58 4.50 3.44 3 47.50 7.77 241.81 42.86 34.43 5.25 10.98 2.48 4 51.75 3.10 191.55 36.79 27.61 3.92 8.11 3.70

[0053] Treatments 2, 3 and 4 all showed significant increases in average fresh plant weight, average dry head weight and average dry seed weight compared to the untreated control thus demonstrating the agronomic efficacy of the composition.