AU2003238563A1

AU2003238563A1 - Fertilisation of soil

Info

Publication number: AU2003238563A1
Application number: AU2003238563A
Authority: AU
Inventors: Gary Murdoch-Brown
Original assignee: Ecotech Pty Ltd
Current assignee: ADVANCED NUTRIENTS Pty Ltd
Priority date: 2002-07-01
Filing date: 2003-06-30
Publication date: 2004-01-19
Anticipated expiration: 2023-06-30
Also published as: AU2003238563B2

Description

WO 2004/002921 PCT/AU2003/000836 FERTILISATION OF SOIL The present invention relates to the fertilisation of soil. In particular, the present invention relates to fertilisers and methods of manufacturing fertilisers whereby the fertilisers increase the use of the 5 applied nutrients by crops farmed in the soil. BACKGROUND Many nutrients applied to soils as fertilisers are lost from the soils via volatilisation and leaching shortly after their application and before the nutrients may be efficiently utilised for the growth or maturing of a crop. As a 10 result, fertilisers are typically applied to soils in quantities significantly in excess of the amounts required to promote plant growth to allow for these losses. Fertilisers leached from such heavily fertilised soils have been found to cause a number of environmental problems, including the promotion of growth of organisms such as algae in waterways and changes to the 15 respective growth patterns of indigenous and introduced species, often leading to the proliferation of introduced species at the expense of indigenous species. Generally it is considered desirable to minimise the amount of fertiliser leached or volatilised from soils as cost of excess fertiliser detracts from the profitability of the crop. Not only does the direct cost of the fertiliser 20 detract from the profitability of the crop but also there are also considerable indirect costs associated with the use of excess fertiliser including transportation costs and application costs. Another approach has been to apply fertilisers to the soil repeatedly throughout the growth cycle of the crop. This approach is costly in 25 terms of labour and also equipment. The repeated application of lesser amounts of fertilisers to the soil is time consuming and increases the complexity of planning the application of the fertiliser so as to avoid disadvantageous weather conditions. Repeated application of fertilisers also increases the wear and tear on application equipment, resulting in increased 30 maintenance and replacement costs. Fertiliser manufacturers have tried to develop fertilisers that release the nutrients to the soil over an extended period. However these delayed release fertilisers are generally costly to produce and the costs WO 2004/002921 PCT/AU2003/000836 2 outweigh the savings resulting from the need to use less fertiliser. Delayed release fertilisers do find use where fertiliser leached from the soil caused substantial environmental damage and the use of delayed release fertiliser can minimise the fertiliser use. 5 There is required a cost effective fertiliser that releases nutrients to the soil over an extended period whereby the quantity of fertiliser leached or volatilized from the soil is minimised without compromising the quantity of nutrients available to the crop. It is also desirable that the number of applications of the fertiliser be minimised. 10 SUMMARY OF THE INVENTION We have found that by the incorporation of humic acids into a fertiliser composition the release of nutrients to the soil from the fertiliser is controlled and a useful fertiliser composition may be produced that overcomes or at least ameliorates one or more of the disadvantages 15 described above, or at least provides the consumer with a useful or commercial choice. In a first broad aspect of the present invention there is provided a solid fertiliser composition comprising a fertiliser and humic acids. "Humic acids" is a general term for a variety of acids of the type 20 similar to the specific acid referred to by organic chemists as "humic acid" and the term will be understood by persons skilled in the art. Persons skilled in the art will understand the term "humic acids" to include acids such as fulvic acid, and ulmic acid. Terminology associated with "humic acids" and their production 25 has the potential to be confusing to those not familiar with its usage. Humic acids are generally derived from plant materials and the production processes are performed and managed by operators that may or may not have a formal chemistry background. As a result in many references the term "humic acid" is used interchangeably with "humic acids". Other terms used in the art to 30 refer to compositions of humic acids include "humic acid derivatives" and "humic acid complex". It will be clear to those skilled in the art the meaning of such terms by the context of their use.

WO 2004/002921 PCT/AU2003/000836 3 DETAILED DESCRIPTION The solid fertiliser composition of the present invention may include a variety of fertilisers apparent to those skilled in the art. The solid fertiliser composition may, in one embodiment, include more than one variety of 5 fertiliser. Suitably the fertiliser may be selected from the group consisting of urea, ammonium salts, ammonium phosphates, lime, rock mineral fertiliser, gypsum, rock phosphate, superphosphates, potassium salts, calcium salts, magnesium salts, trace metal salts, and combinations thereof. 10 We have found that the incorporation of humic acids into a solid fertiliser composition containing urea produces a particularly advantageous urea-based fertiliser. In a first preferred embodiment of the present invention there is provided a solid fertiliser composition comprising urea and humic acids. The urea may be in any solid form including granular or prilled form. 15 Humic acids are a product generally produced from plant material, such as from leonardite, lignite or peat. Other acids or plant derivatives produced by these processes are also generally referred to as humic acids. The solid fertiliser composition of the present invention may include a variety of humic acids that will be apparent or available to those skilled in 20 the art. The humic acids may be used in the fertiliser composition of the present invention in any convenient form. In one embodiment chemically pure humic acid may be used. Alternatively chemically pure fulvic acid, ulmic acid, or other acids generally known as humic acids may be used. It is preferred that the humic acids selected for use in the solid fertiliser 25 composition be derived from plant material and include a mixture of humic acids. Humic acids typically is supplied in a composition as a liquid or dry humate and may include a variety of amino acids, microbes, vitamins and trace elements. Such additional components found in the humic acids 30 composition may also be beneficial to the soil. We have found that compositions comprising humic acids that include amino acids advantageously increases the retention of the fertiliser in the soil. Therefore, in a preferred embodiment of the present invention there WO 2004/002921 PCT/AU2003/000836 4 is provided a solid fertiliser composition comprising a fertiliser, humic acids and amino acids. The proportion of humic acids in the solid fertiliser composition of the present invention is preferably in the range of from 0.03% by weight to 4% 5 by weight, more preferably in the range of from 1% by weight to 2% by weight. Typically the humic acid is supplied in a solution containing 10-38% humic acids. It is preferred that such solutions are added in a proportion that results in the final fertiliser composition having the desired amount of humic acids present. 10 The humic acids may be incorporated in the fertiliser as part of the process by which the fertiliser is manufactured. For example, in the manufacture of urea, a melt of urea is produced at about 1300C. Humic acids may be added to the melt of urea or during the solidification process. Urea is solidified to form prills or granules. Humic acids may be added to the urea 15 during the prilling or granulation process. Processes whereby humic acids are incorporated into the fertiliser during the manufacture of the fertiliser granules preferably employs a concentrated solution or neat humic acids. Alternatively, humic acids are applied to the fertiliser as a coating. We have found that applying a solution of humic acids to a fertiliser such as 20 urea provides a fertiliser composition that maintains nutrients availability to the soil over an extended period and allows a lesser amount of fertiliser to be applied to the soil. Applying humic acids as a coating is a particularly advantageous method of incorporating humic acids to the fertiliser. By applying the humic acids as a coating to a preformed granule of fertiliser 25 lessens the likelihood of the humic acids being disadvantageously affected by the incorporation process. By introducing the humic acids into a melt of a fertiliser such as urea there is a potential for humic acids and components in humic acids compositions to partially decompose as a result of the temperature and/or pressure of the melt. Thus, applying the humic acids as 30 coating to a preformed granule allows the humic acids to be incorporated into the solid fertiliser composition at a lower temperature. We have found that a 22% solution of humic acids such as those generally supplied from WO 2004/002921 PCT/AU2003/000836 5 commercial humic acids suppliers as "technical humic acid" may be directly applied to a fertiliser such as urea. Preferably the humic acids are applied at a level that does not substantially dissolve the granulated fertiliser. We have found that by 5 applying 10 to 20 litres per tonne of a 22% solution of humic acids and preferably 18 litres per tonne permits the application of a sufficient amount of humic acids to the fertiliser without substantially dissolving prilled or granulated urea. The humic acids solution may be sprayed onto prilled or granulated fertiliser. 10 Preferably the granules of fertiliser are sprayed with humic acids whilst being tumbled. The granules may be tumbled as the granules are moved along a conveyer or tumbled in a rotary tumbler, such as the type used for applying anti-caking agents or trace element coatings. Other types of tumblers may be used that present granules for spraying with humic acids. 15 The coated granules may preferably be dried in a trommel drier, solar drier or fluidised bed drier. The dried granules may then be collected for transport or storage. Other constituents may be incorporated with the humic acid, for example technical humic acids generally are produced with amino acids, 20 microbes, vitamins, and other trace elements. Selected soil enhancers, emollients and other auxiliary materials may be incorporated with the humic acids sprayed onto the granules. The present invention also includes the manufacture of a solid fertiliser composition. In a second aspect of the present invention there is 25 provided a method for the manufacture of a solid fertiliser composition comprising the steps of blending a liquid fertiliser with a solution of humic acids and solidifying the blend to form a solid fertiliser composition. The humic acids may be added to inorganic and organic fertiliser in the manufacturing process to enhance the qualities of the fertiliser. During 30 manufacture many fertilisers are produced as a liquid, melt or slurry. The final liquid phase is piped to a prilling tower, granulator or pelletiser for final conversion to a solid granule. The humic acids are metered at the required rate via a holding tank and dosing pump into an in-line mixer installed WO 2004/002921 PCT/AU2003/000836 6 immediately prior to the prilling tower, granulator or pelletiser. Solid conversion is carried out by conventional means, as is subsequent storage, handling and packaging. In a third aspect a solid fertiliser may be coated with humic acids to 5 form the solid fertiliser composition of the present invention. Accordingly there is provided a method for the manufacture of a solid fertiliser composition comprising the steps of spraying humic acid in solution onto a solid fertiliser; and drying the humic acids coated fertiliser to form the solid fertiliser composition. 10 Pre-manufactured granular, pelletised, or prilled fertiliser (urea) may be coated with humic acids to enhance the qualities of the fertiliser. Into the receiving hopper, fertiliser may be introduced by mechanical (loader, excavator) means or an automatic or semi-auto auger or conveying system. Fertiliser may be gravity fed into a rotating trommel drum fitted with 15 a series of spray bar(s) and lifting fins. Coating solution of humic acids are metered through the spray bars and the granules are treated with a fine spray at the applicable rate. The repeated lifting and falling throughout the trommel promotes an even coating and begins the drying step. A one trommel system may incorporate a forced heated air system 20 at the exit of the trommel, forcing hot air back through the trommel to ensure complete and rapid drying at exit of the dryer. Such a system would be inherently long and would command a significant footprint. For this reason, a dual trommel under and over configuration is more suited to commercial enterprise. 25 In a duel system, the fertiliser may be fed into the top trommel where the humic acids coating is applied and drying initiated, the coated fertiliser may be gravity fed to a lower receiving hopper to feed into the lower drying trommel operating counter to the upper. The drying trommel can be fitted with a forced heated air system a the exit of the trommel, forcing heated 30 air back through the trommel to ensure complete and rapid drying at exit of the dryer. On exit the coated fertiliser can be stored, handled and packaged. Whilst not wishing to be bound by theory it is believed that the cation exchange capacity and/or the reduction in urea hydrolysis speed in the WO 2004/002921 PCT/AU2003/000836 7 humic acid complex provides the mechanism that results in the enhanced delivery of the nutrients from the fertiliser to the crop. The present invention will now be illustrated with reference to the following non-limiting example: 5 Example 1 Granular urea was sprayed with Enhance (Western Nutrients Corporation USA and supplied by Advanced Nutrients Pty Ltd) at a rate of 15 litres per tonne. The Enhance was sprayed onto the granular urea whilst the granular urea was being transported on a conveyer. The sprayed urea was 10 rotary kiln dried and transported for application to the soil for fertilising a crop. Subsequent controlled, replicated field trails were performed in with the following results: Theoretical Net BARLEY Yield (t/ha) Protein (%) Return AU$/ha Return (AU$/ha) Control - no fertiliser 2.38 10.1 $737.80 Normal urea @ 80kg/ha 3.63 12.0 $1096.50 Coated urea @ 50kg/ha 3.71 14.3 $1120.40 Theoretical Net SORGHUM Yield (t/ha) Protein (%) Return AU$/ha Return (AU$/ha) Control - no fertiliser 5.90 8.3 $944.00 Normal urea @ 80kg/ha 6.50 9.5 $1007.24 Coated urea @ 80kg/ha 6.99 11.8 $1069.60 Coated urea @ 50kg/ha 6.82 11.6 $1060.70 15 Example 2 Granular urea was sprayed with Enhance (Western Nutrients Corporation USA and supplied by Advanced Nutrients Pty Ltd) at a rate of 18 litres per tonne. The Enhance was sprayed onto the granular urea being mixed in a horizontal auger mixer. The sprayed urea was rotary kiln dried and 20 transported for application to nitrogen deficient soil to measure nitrogen retention under varying moisture conditions. Subsequent controlled, replicated pot trials were performed with the following results: WO 2004/002921 PCT/AU2003/000836 8 NITROGEN RETENTION IN SOIL (%) Low Moisture 2 weeks 4 weeks 6 weeks 8 weeks 10 weeks Coated Urea 95 84 75 70 62 Uncoated Urea 55 30 15 3 1 5 Low- Medium Moisture 2 weeks 4 weeks 6 weeks 8 weeks 10 weeks Coated Urea 93 85 70 63 52 Uncoated Urea 66 45 28 10 4 Optimum Moisture 2 weeks 4 weeks 6 weeks 8 weeks 10 weeks Coated Urea 90 80 65 52 46 Uncoated Urea 75 42 26 8 5 Moderately High Moisture 2 weeks 4 weeks 6 weeks 8 weeks 10 weeks Coated Urea 90 76 65 50 45 Uncoated Urea 68 40 15 4 3 10 Very High Moisture 2 weeks 4 weeks 6 weeks 8 weeks 10 weeks Coated Urea 85 70 60 52 48 Uncoated Urea 60 35 10 2 1 It will be understood by persons skilled in the art that the present invention described herein is capable of modification without departing from 15 the spirit and scope of the disclosure. Such modifications form part of the invention described herein.

Claims

1. A solid fertiliser composition comprising a fertiliser and humic acids.

2. A solid fertiliser composition according to claim 1 wherein the 5 fertiliser is selected from the group consisting of urea, ammonium salts, ammonium phosphates, lime, rock mineral fertiliser, gypsum, rock phosphate, superphosphates, potassium salts, calcium salts, magnesium salts, trace metal salts, and combinations thereof.

3. A solid fertiliser composition according to claim 1 wherein the 10 fertiliser is urea.

4. A solid fertiliser composition according to claim 1 wherein the humic acids are produced from plant material selected from the group consisting of leonardite, lignite and peat.

5. A solid fertiliser composition according to claim 1 wherein the himic 15 acids consist of a chemically pure acid selected from the group consisting of humic acid, fulvic acid and ulmic acid.

6. A solid fertiliser composition according to claim 1 wherein the humic acids comprise a mixture of humic acids.

7. A solid fertiliser composition according to claim 6 wherein the 20 humic acids further comprises other derivatives from plant material selected from the group consisting of amino acids, microbes, vitamins and trace elements.

8. A solid fertiliser composition comprising a fertiliser, humic acids and amino acids. 25

9. A solid fertiliser composition according to claim 1 wherein the proportion of humic acids in the solid fertiliser composition of the present invention is preferably in the range of from 0.03% by weight to 4% by weight of fertiliser.

10. A solid fertiliser composition according to claim 1 wherein the 30 proportion of humic acids in the solid fertiliser composition of the present invention is preferably in the range of from 1% by weight to 2% by weight of fertiliser. WO 2004/002921 PCT/AU2003/000836 10

11. A method for the manufacture of a solid fertiliser composition comprising the steps of blending a liquid fertiliser with a solution of humic acids and solidifying the blend to form a solid fertiliser composition.

12. A method for the manufacture of a solid fertiliser composition 5 comprising the steps of spraying humic acid in solution onto a solid fertiliser; and drying the humic acids coated fertiliser to form the solid fertiliser composition.