GB2241498A

GB2241498A - Plant micro-element availability

Info

Publication number: GB2241498A
Application number: GB9104148A
Authority: GB
Inventors: Johannes Dekker; Heerden Van Der Watt Hendr Van; Robin Oxley Barnard; Izak Johannes Cronje
Original assignee: NAT ENERGY COUNCIL; National Energy Council
Current assignee: NAT ENERGY COUNCIL; National Energy Council
Priority date: 1990-02-28
Filing date: 1991-02-27
Publication date: 1991-09-04
Anticipated expiration: 2011-02-27
Also published as: ITMI910504A0; ITMI910504A1; GB9104148D0; AU634025B2; FR2658810A1; GB2241498B; FR2658810B1; DE4105247A1; IT1249342B; JPH04214085A; AU7124191A

Abstract

A composition for applying trace elements such as iron, zinc, manganese or copper to a soil locus, particularly a basic soil locus is provided. The composition provides the trace element in a form which is suspended or complexed with coal-derived humic acids in an aqueous medium, or captured in or by an oxidised coal, or a mixture thereof.

Description

1 1 :2:;2> A, X tl ---3 t3 "PLANT MICRO-ELEMENT AVAILABILITY" This

invention relates to the supply of micro-elements, or trace elements as they are also known, such as Fe, Zn, Mn and Cu, to plants in soils where problems are experienced with uptake of these elements.

It is well known that the availability of several trace elements, especially Fe and Zn, decreases at high pH, creating nutritional problems under these conditions.

In order to alleviate these problems, use is often made of synthetic organic chelates added to the soil, which are usually both expensive and not very efficient. Alternativel, foliar applications are made. y According to the present invention, a composition for applying to a soil locus, particularly a basic soil, includes a trace element such as Fe, Zn, Mn or Cu in one or both of the following forms:

i. suspended or complexed with coal-derived humic acids in an aqueous medium; ii. captured in or by an oxidised coal.

1 2 - Further according to the invention, a method of applying a trace element to a basic soil locus includes the step of applying a composition as described above to that locus.

Still further according to the invention, a method of improving the uptake of a trace element by a plant from a basic soil locus includes the step of applying a composition as described above to the locus in the region of the plant.

The oxidised coal will preferably be an oxidised low to medium ranked coal. Examples of such coals are sub-bituminous and bituminous coals. The oxidised coal is preferably produced by the wet oxidation process described in United States patent No. 4,912,256. This process produces an oxidised coal which contains humic acids. The oxidised coal has an acidic pH, for example a pH in the range 2 to 3. The trace elements are captured by this oxidised coal by contacting it with an aqueous solution of the trace element. Typically, the aqueous solution is a sulphate solution. The trace element is captured by the oxidised coal and is subsequently made available to the plant growing in the alkaline soil.

1 - 3 In the production of an oxidised coal using a wet oxidation process, some water-soluble fulvic acids will also he produced. The fulvic acids can be removed from the oxidised coal (by filtration) before treatment with the solution of the trace element. However, it is not necessary to remove the fulvic acids from the oxidised coal.

The humic acids for the practice of the invention are preferably produced from an oxidised coal, particularly an oxidised low to medium ranked coal. The humic acids will he mixed with an aqueous solution of a trace element. The trace element will be either complex with the humic acids or will be suspended with the humic acids, in both cases in the aqueous medium. The trace element will be used in this form for application to a soil locus.

The coal-derived humic acids and the oxidised coal will typically have an elemental analysis (on an air-dried basis) of.

Element Carbon Hydrogen Oxygen Range (%) 45-70 2 - 6 20-40 The coal-derived humic acids and oxidised coal will also typically have a functional group analysis of.

Functional Group Total acidity Carboxylic groups Phenolic groups Range (meq/c) c 3 - 13 0,5- 12 0,5- 9 Trace elements, particularly iron and zinc, are not easily taken up by a plant from basic soils because the trace element or a proportion thereof, will exist in such soils in insoluble form. The trace elements in the compositions of the invention are in a form which enable them to he taken up by a plant from these basic soils in a way which makes them readily accessible to the metabolic processes of the plant.

The invention will now be illustrated with the following example.

PREPARATION A bituminous coal (200g) and water (400mi) were slurried in a 2 litre stirred reactor. The reactor was pressurised to 8,0 MPa with oxygen, heated with external bar heaters to 2000C. Oxygen was allowed to flow through the slurry at a rate of 4 litres/minute. After one hour the 5 oxygen flow was terminated, the reactor cooled down -to room temperature and the pressure released to atmospheric.

The slurry contained oxidised coal (insoluble in water and hereinafter referred to as 'oxicoal") and a solution of fulvic acids in water. By filtration, the oxicoal was separated from the solution of fulvic acids in water. The concentration of the fulvic acids in water was determined to be 8,45% (on a mass per volume basis). The oxicoal was found to have the following elemental analysis (on an air-dried basis) and functional group analysis:

Elemental Anaksis Element Carbon Hydrogen Oxygen Functional Group Anglysis Functional Group Total acidity Carboxylic groups Phenolic groups Percentage 51,3 2,3 28,7 Amount (meq/g) 6,25 2,16 4,09 6 - Humic acids were obtained by refluxing the oxicoal slurry with aqueous sodium hydroxide for 5 hours. The insoluble residue was removed by centrifugation and the humic acids (80% yield) were recovered by acidic precipitation of the supernatant. This will be referred to as "oxihumic acids".

The oxihumic acids were found to have the following elemental analysis (on an air-dried basis) and functional group analysis:

q.

Elemental Analysis Element Carbon Hydrogen Oxygen Function Group Analysis Functional Group Total acidity Carboxylic groups Phenolic groups Percentage 55.5 2,7 32,1 Amount (meq/c) 0 7,45 3-38 4,07 Fe AND Zn OXIHUMIC ACIDS FORMULATION The oxibumic acids were mixed with 0,1 M solutions of Fe and Zn sulphate to obtain a concentration of 7,21 and 8,44 meq/mi of Fe and Zn respectively in the formulation.

Fe AND Zn OXICOAL FORMULATION The oxicoal was mixed with 0,1 M solutions of Fe and Zn sulphate. The thus formulated oxicoals were filtered off and dried.

The formulated oxicoals were analysed and found to contain 10,4% Fe and 0, 37% Zn.

APPLICATION PROCEDURE A sand culture experiment, using 4kg quartz sand in 1Mitscherlich vegetation vessels, was conducted. Hoagland nutrient solution. containing nitrogen as both NH, and NO,, but excluding both Fe and Zn. was supplied initially and augmented during the growing season. Iron. at the rate of 0, 5 mg/dm', or zinc. at the rate of 0,05 mg/dm, were supplied to the vessels in appropriate treatments as different sources: control (0), sulphate, EDTA, oxihumic acids, and oxicoal.

8 Two levels of liming were employed: the equivalent of 10t and 20t/ha 30Omm depth of calcium carbonate (AR), which was thoroughly incorporated prior to the commencement of the experiment. Maize (Zga mays cv TX24) was used as test crop, with rye plants per pot and three replicates of each treatment. Plant growth was monitored and photographs taken at appropriate growth stages.

Both tops and roots were harvested, at approximately 14 weeks, and dry (650C) mass deterTnined. Fe and Zn were also determined in both tops j. and roots according to the method of Barnard, FLO. and F61scher, Wj. 1988, Growth of Legumes at Different Levels of Liming, Trop. Agric. (Trinidad) 65 (2): 113-116.

For standard statistical analysis the two aspects of the experiment, Fe and Zn, were considered separately, which is how the respective data is presented. The Tukey test at the 5% level of significance was carried out according to Steel, R.G.D. and Torrie, J.H., 1980, "Principles and Procedures of Statistics" MeGraw-Hill Book Corporation, New York.

RESULTS The results are given in Tables 1 and 2 for iron and in Tables 3 and 4 for zinc.

-g- RESULTS TABLE 1 Yield and Fe-content of top growth of maize with different Fe treatments Top growth yield Fe-content of top growth Treatment (T) g/pot (M9 1 loo/pot) lot 20t T- lot 20t T- CaC03 CaCO3 aeans, CaCO3 CaCO3 means Control-FE 58.05 59.24 58,64 357 397 375 Sulphate 57.08 56.89 56.98 227 340 283 EDTA 71.55 64.29 67.92 214 225 219 Oxihumic Acids 66.85 68.50 67.68 267 380 324 Oxicoal 64.19 61.41 62.80 369 338 353 Lime Level (L) means 64.69 63.83 296 343 LSDT (5%) for Treatment (T) 9.62 168 Lime Level JL) 3,69 64 C.V. 8.3 20.0 TABLE 2 Yield and Fe-content of roots of maize with different Fe treatments Root yield Fe-content of roots Treatment (T) (91pot) (M9 X 100/P0t) lot 20t T- lot 20t T- Cac03 CaC03 means Cac03 CaCO3 means Control-Fe 22.70 22.25 22,47 736 990 863 Sulphate 21.50 25.67 23.58 943 659 801 EDTA 28.11 21.58 24.85 1277 661 969 Oxihumic acids 25.28 27.55 26.42 519 1624 1071 Oxicoal 26.58 24.92 25.75 1099 670 885 Lime level (L) reans 24.93 25.86 923 1175 LSDT (5%) for:

Treatment (T) 6.15 1208 Lime Level (L) 2.35 462 C.V. 13.0 62.0 TABLE 3 Yield and h-contlent of roots of maize with different h treatments Top growth yield h-content of top growth Treatment (T) (g/Pot) (M9 X 100/pot) lot 20t T- lot 20t T- Cac03 Cac03 means CaC03 CaCO3 means Control-h 74.94 68.15 71.55 180 82 131 Sulphate 67.95 75.28 71.62 74 84 79 EDTA 82.03 78.40 80.22 78 Oxihumic acids 78.89 93.19 86.04 308 323 315 Oxicoal 80.23 88.71 84.47 453 470 461 Lime level (L) means 77.72 82.69 (293) 236 LSDT (5) Treatment (T) 7.72 101 Lime level (L) 2.96 72 C.V. % 5.0 14.D non-est.

TABLE 4 Yield and h-content of roots of maize with different Zn treatments Root yield h-content of roots Treatment (T) (g/Pot) (M9 1 100/pot) lot 20t T- lot 20t T- CaCO3 CaC03 means CaC03 Cac03 means Control-h 19.62 27.67 23.65 35 33 34 Sulphate 27.99 21.31 24.65 68 24 46 EDTA 29.16 28.21 28.69 36 36 38 Oxihumic acids 23.92 22.97 23.45 229 174 201 Oxicoal, 25.61 25.57 26.59 253 263 258 Lime level (L) teans 25.80 25.70 1 149 134 LSDT (5%) for:

Treatment (T) 6.31 49 Lime level (L) 2.93 19 C.V. 14.0 19.0 CONCLUSION

From the results set out in Tables 1 to 4 it can be seen that in many instances excellent uptake of Iron and zinc from soils of high pH levels was achieved with both oxihumic acids and oxicoal. However, it should be noted that the amount of iron and zinc taken up by the plant is not always a true reflection of the quality of the iron and zinc which is made available to the plant. Both the oxicoal and oxihumic acids provided excellent iron and zinc metabolites to the plant which is mirrored in the appearance of the plant. For example, maize treated with the iron and zinc oxicoal and oxihumic acids exhibited a far better quality than the maize treated with the iron and zinc EDTA or the iron and zinc sulphate. The plants had a more healthy appearance, the -leaves were more shiny and had a deeper shade of green, indicating that the iron and zinc taken up from the oxidised coal derived products provided the plant with a more accessible source of iron and zinc for the metabolic processes of the plant. There is also a very major cost advantage, i.e. in excess of 10 times, with the use of an iron and zinc oxicoal in comparison with an iron and zinc EDTA product.

Claims

CLAINITS

1. A composition for applying to a soil locus includes a trace element in a form selected from:

(1) suspended or complexed with coal-derived humic acids in an aqueous medium; (H) captured in or by an oxidised coal; (iii) mixtures of (i) and (H).

2. A composition according to claim 1 wherein the trace element is selected from iron, zinc, copper, manganese and mixtures thereof.

3.

composition A dk -- according to claim 1 wherein the trace element is selected from iron, zinc and mixtures thereof.

1 t -13

4. A composition according to any one of claims 1 to 3 wherein the coal from which the humic acids have been derived is an oxidised low to medium ranked coal.

5. A composition according to any one of claims 1 to 3 wherein the oxidised coal is an oxidised low to medium ranked coal.

6. A composition according to any one of the preceding claims wherein the humic acids and oxidised coal have an elemental analysis (on an airdried basis) of..

Element Carbon Hydrogen Oxygen Range ( %) 45-70 2- 6 20-40 -14

7. A composition according to any one of the preceding claims wherein the humic acids and oxidised coal have a functional group analysis of..

Functional Group Total acidity Carboxylic groups Phenolic groups

8. A composition according to any one of the preceding claims wherein the oxidised coal has an acidic pH.

Range (meq/g) 3-13 0,5-12 0,5-

9 9. A composition according to claim 8 wherein the oxidised coal has a pH in the range 2 to 3.

10. A composition according to claim 1 and substantially as hereinbefore described.

11. A method of applying a trace element to a basic soil locus includes the step of applying a composition according to any one of the preceding claims to that locus.

12. A method of improving the uptake of a trace element by a plant from a basic soil locus includes the steps of applying a composition according to any one of claims 1 to 10 to that locus in the region of a plant.

PnhImhed 199 1 w The patent Office. Concer)l House. Cardifl. Road. NeAporL. Gwent NP9 1 RH. Further copies may be obtained from -- - - -unier. k-onceux tiou.c. ---- -.u. inpuvL. uwcnx iNr-to P urLner copies may tie ot)tatnea-irom-