Method and use of zeolites

Abstract

Disclosed herein is a method comprising applying a synthetic zeolite to soil.

Description

METHOD AND USE OF ZEOLITESField

[0001] The invention generally relates to methods and uses of synthetic zeolites in the protection of soil carbon.Background

[0002] Soils are an enormous carbon (C) pool, globally hosting more than 3500 gigatons C. Soils therefore play a key role in climate change, acting as both a source and sink for organic and inorganic C compounds in the environment. In addition to climate change regulation, soils are a fundamentally important substrate for food and fibre production with general findings suggesting that overall soil health is declining.

[0003] A common approach to improve agricultural soil condition is the practice of mulch and compost addition (organic amendments) to fallow soils prior to planting. The main objectives of adding organic amendments to soils are to maintain soil moisture, improve nutrient retention and minimise weed growth. Mulches are typically carbon-rich materials, such as wheat straw, peat moss or even plastic, whereas composts are more microbially degraded organic products that generally have lower carbon / nitrogen ratios.

[0004] Although the addition of organic amendments to soils has been shown to be beneficial for general soil nutrient and water retention dynamics, there is little evidence that they result in increased soil carbon and organic matter stocks. In fact, the addition of organic amendments has in some instances, achieved the opposite outcome. This is thought to be through a process known as ‘priming’ where the application of a C-rich source stimulates the existing soil microbial community to degrade existing soil C compounds as well as the added C-source.

[0005] It is desirable to provide a method for improving protection of soil carbon and / or organic matter stocks. It is an object of the invention to address at least one shortcoming of the prior art and / or provide a useful alternative.Summary of Invention

[0006] In a first aspect of the invention, there is provided a method comprising applying a synthetic zeolite to soil.

[0007] In an embodiment, the soil is tilled or ploughed, either during the application of the synthetic zeolite or subsequent to the application thereof, to mix the synthetic zeolite into the soil.

[0008] In an embodiment, applying the synthetic zeolite to soil comprises applying the synthetic zeolite to soil over an area in an amount of from about 0.5 t.ha'1(0.05 kg.m'2) up to about 20 t.ha'1(2 kg.m'2). Preferably, the amount is from about 1 t.ha'1(0.1 kg.m'2). Preferably the amount is up to about 10 t.ha'1(1 kg.m'2).

[0009] In an embodiment, the synthetic zeolite is Linde Type A (Na2O-AhO3-2SiO2-2.25H2O) zeolite or a Type X zeolite. Preferably, the zeolite is Type A zeolite.

[0010] In an embodiment, the synthetic zeolite is in the form of pellets or particles having a D50 of 5 mm or less. Preferably, the pellets or particles have a D50 is 4 mm or less. Additionally or alternatively, it is preferred that the pellets or particles have a D50 particle size of at least 1 mm. Preferably, the pellets or particles have a D50 particle size of at least 2 mm. In one example, the pellets or particles have a D50 that is about 3 mm ± 10%.

[0011] In an embodiment, the synthetic zeolite has a primary D50 particle size of 300 pm or less. Preferably, the primary D50 particle size is 200 pm or less. More preferably, the primary D50 particle size is 200 pm or less. Most preferably, the primary D50 particle size is about 100 pm ± 10%.

[0012] In one form of the above embodiment, the zeolite is in the form of a pellet comprising zeolites of primary particles, with the primary particles and pellets having D50 sizes as discussed above. The pellets preferably comprise a binder. The inventors have found that a binder comprising gypsum and / or kaolinite is particularly useful since these materials permit the pellets to gradually break down in soil and release the zeolite. Further, gypsum is itself a beneficial agricultural soil input.

[0013] In an embodiment, the synthetic zeolite has a surface area of at least 100 m2 / g. Preferably, the surface area is at least 120 m2 / g. More preferably, the surface area is at least 140 m2 / g. Even more preferably, the surface area is at least 160 m2 / g. Most preferably, the surface area is at least 180 m2 / g.

[0014] In an embodiment, the synthetic zeolite comprises pores, wherein at least 65% of the pores have a pore diameter of about 4 A ± 10%.

[0015] In an embodiment, the step of applying the synthetic zeolite to the soil comprises applying a composition comprising the synthetic zeolite to the soil, the composition further comprising a source of bioavailable nitrogen.

[0016] In one form of the above embodiment, the composition further comprises a source of bioavailable phosphorous and / or a source of bioavailable potassium.

[0017] In one form of the above embodiment, the composition has sufficient nitrogen to provide a soil C / N ratio of less than 25 on application of the composition to the soil.

[0018] In a second aspect of the invention, there is provided a soil treatment composition comprising a synthetic zeolite and a source of bioavailable nitrogen.

[0019] In an embodiment, the synthetic zeolite is Linde Type A (NaiO- AhO3-2SiO2-2.25H2O) zeolite or a Type X zeolite. Preferably, the zeolite is Type A zeolite.

[0020] In an embodiment, the soil treatment composition further comprises a source of bioavailable phosphorous and / or a source of bioavailable potassium.

[0021] In an embodiment, the zeolite and / or the source of bioavailable nitrogen is in the form of pellets or particles with a D50 of 5 mm or less. Preferably, the pellets or particles have a D50 is 3 mm or less. More preferably, the pellets or particles have a D50 is 2 mm or less. Most preferably, the pellets or particles have a D50 is 1 mm or less.

[0022] In one form of the above embodiment, the zeolite is in the form of pellets.

[0023] In embodiments in which the zeolite is in the form of pellets, it is preferred that the pellets further comprise a binder. Preferably the binder comprises, consists of, or consists essentially of gypsum and / or kaolinite.

[0024] In embodiments in which the zeolite is in the form of pellets, it is preferred that the synthetic zeolite has a primary Dso particle size of 300 pm or less. Preferably, the primary Dso particle size is 200 pm or less. More preferably, the primary Dso particle size is 200 pm or less. Most preferably, the primary Dso particle size is about 100 pm ± 10%.

[0025] In an embodiment, the synthetic zeolite has a surface area of at least 100 m2 / g.Preferably, the surface area is at least 120 m2 / g. More preferably, the surface area is at least 140 m2 / g. Even more preferably, the surface area is at least 160 m2 / g. Most preferably, the surface area is at least 180 m2 / g.

[0026] In an embodiment, the soil treatment composition further comprises a source of bioavailable phosphorous and / or bioavailable potassium. In embodiments in which the zeolite is in the form of pellets, it is preferred that the pellets further comprise the source of bioavailable phosphorous and / or bioavailable potassium.

[0027] In an embodiment, the zeolite comprises pores, and at least 65% of the pores have a pore diameter of about 4 A ± 10%.

[0028] In a third aspect of the invention, there is provided the use of a soil treatment composition according to the second aspect and / or embodiments thereof and / or forms thereof in to treat soil for the protection of soil carbon therein. The soil carbon may be inorganic or organic soil carbon.

[0029] Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and / or combined with other pieces of prior art by a skilled person in the art.

[0030] As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps.Brief Description of Drawings

[0031] Figure 1: Graph showing particle size distribution profiles for the two soils used in the trial example.

[0032] Figure 2: Graph showing high (maximum)-low (minimum)-close (mean) plots for predicted Corg contents for treatments at the end of the trial example. Ctrl = soil+OM source (no mineral), MZ1 = manufactured zeolite 1, MZ2 = manufactured zeolite 2, NZ = natural zeolite, B = bentonite. N=4 for each treatment, *denotes values that are significantly different (p<0.05) from control.

[0033] Figure 3: Estimated carbon protection for treatments that showed significantly higher predicted Corg concentrations relative to controls. HSAIM abbreviations: MZ1 = manufactured zeolite 1, MZ2 = manufactured zeolite 2, NZ = natural zeolite, B = bentonite. N=4 for each treatment. Upper and lower bars are standard errors of the mean.

[0034] Figure 4: C / N ratio plots for A) Peat moss + Arenosol, B) Cow manure + Arenosol, C) Peat moss + Vertisol, and D) Cow manure + Vertisol treatments. MZ1 = manufactured zeolite 1, MZ2 = manufactured zeolite 2, NZ = natural zeolite, B = bentonite. Green arrow represents ratio shift away from soil towards organic input source (p<0.05): Black arrows represent ratio shift towards soil away from organic input source (p<0.05).

[0035] Figure 5: Graph showing high (maximum)-low (minimum)-close (mean) plots for organic matter contents for treatments at the end of the trial. Ctrl = soil+OM source (no mineral), MZ1 = manufactured zeolite 1, MZ2 = manufactured zeolite 2, NZ = natural zeolite, B = bentonite. N=4 for each treatment, *denotes values that are significantly different (p<0.05) from control.

[0036] Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.Description of Embodiments

[0037] The invention generally relates to a method of treating soil with a synthetic zeolite. The method broadly comprises applying an amount of the synthetic zeolite over a surface area of the soil. The soil may then be tilled or ploughed, either during the application of the synthetic zeolite or subsequent to the application thereof, to mix the synthetic zeolite into the soil.

[0038] The inventors have found that high surface area inorganic minerals (HSAIM) are useful for protecting organic carbon in soils, and thus are useful to minimize the degradation or depletion of organic carbon in soils, particularly where organic inputs are added to fallow soils prior to planting. As discussed in the background section, the addition of organic amendments to soils can result in a ‘priming’ process whereby the existing soil microbial community is stimulated to degrade existing soil carbon compounds as well as the added organic amendments.

[0039] Synthetic zeolites (which are also referred to as manufactured zeolites herein) have been found to be particularly effective at protecting the organic carbon content of soils, and offer improved protection as compared with non-zeolitic HSAIM materials, such as clays and surprisingly also over natural zeolites.

[0040] By ‘synthetic zeolite’ it is meant a zeolite which is manufactured using, e.g., commercial processes. The term ‘synthetic zeolite’ may be used synonymously with ‘manufactured zeolite’. Most synthetic zeolites do not commonly exist naturally within the environment. Synthetic zeolites often contain unique frameworks which are difficult to find in nature. Examples of synthetic zeolite include zeolite Linde Type A and zeolite Linde Type X, etc.

[0041] By ‘natural zeolite’ it is meant a zeolite which is commonly found in nature. These zeolites are typically formed following crystallisation of ash and rocks in response to contact with alkaline groundwater and lakes. Examples of natural zeolite include stilbite and clinoptilolite, etc. It is pointed out that some zeolites, such as faujasite and zeolite A are found in nature in rare instances. However, these natural forms of faujasite and zeolite A are not typically available in commercial quantities, and as such, these are typically manufactured to meet demand. Given this, those skilled in the art consider faujasite and zeolite A to be synthetic zeolites since they are manufactured on a commercial scale using industrial processes.

[0042] Without wishing to be bound by theory, the inventors are of the view that the improved performance of synthetic zeolites over natural zeolites is due to the framework of pores being smaller and more uniform in size. The inventors have found that these smaller and more uniform pores provide synthetic zeolites with substantially larger exposed surface area than natural zeolites, and this results in synthetic zeolites having cation exchange capacities that are significantly higher than in comparison with natural zeolites or other high surface area materials, such as biochar. By way of example, synthetic zeolites may have cation exchange capacities 3x higher (or more) than that of natural zeolites, and 4x higher (or more) than that of biochar. Furthermore, synthetic zeolites are generally substantially free of impurities which have a deleterious effect on, for example, ion exchange capacity.

[0043] In contrast, a natural zeolite will exhibit less consistency in their pore size and have many more chemical elements incorporated within their structure due to their formation processes, such as from volcanic and sedimentary rocks, such as chabazite, clinoptilolite, and mordenite. Thus, even if a zeolite is naturally available, a synthetically produced version of this zeolite offers superior performance in the context of the invention since it has controlled pore sizes with narrower pore size distribution and higher purity.Example

[0044] The following example reports the results from testing the effectiveness of synthetic zeolites HSAIM in protecting organic carbon in soil. Two manufactured zeolites, zeolite A and zeolite X, were investigated, and the performance of these in protecting soil carbon was compared against two other HSAIM, a natural zeolite and a bentonite clay.

[0045] The example also considered the addition of soil amendments in the form of a carbon- rich (peat moss) and carbon-poor (composted cow manure) organic matter (OM) source.

[0046] The HSAIM and organic sources were incorporated into a microbially active (clayey Vertisol) and inactive (sandy Arenosol) soil. The treatments were incubated for three months under laboratory conditions and were subjected to continuous wetting-drying cycles, before being analysed for carbon loss.

[0047] The example and results are discussed in more detail below.Materials

[0048] Two typical but contrasting soils were used in this example: (1) a clayey Vertisol and (2) a sandy Arenosol. Both soils were collected from the Southeast region of Queensland in Australia. The Vertisol was acquired from a horticultural farm while the Arenosol was obtained from a buffer strip adjoining a cattle grazing farm. The soils were air-dried and sieved to <2mm.

[0049] Two manufactured / synthetic zeolites, one Type A (denoted MZ1) and one Type X (denoted MZ2) were provided by an Australian commercial supplier (Zeotech Pty Ltd). A naturally occurring clinoptilolite zeolite (denoted NZ) was obtained from an Australian supplier, while a sodium bentonite (i.e., montmorillonite ‘B’) sourced from western Queensland was also used. Particle sizes for all materials were finer than 1mm. A peat moss and composted cow manure sample were obtained from a commercial landscape supplier.Incubation trial

[0050] The incubation trial was performed following a factorial design: 2 soil types x 2 organic matter sources x 5 HSAIMs (4 minerals + 1 no addition as control) x 4 replicates. ‘Soil only’ treatments were also established (2 soils x 4 replicates) tallying a total sample number of 88.

[0051] Initially, soils were placed into 100 ml glass incubation vessels to a depth of 5 cm, equating to a volume of 30 ml (30 g for the lighter Vertisol and 50 g for the denser Arenosol). The organic matter amendments were then added at rates of 60 t.ha'1, which was selected as a loading rate since it is a mid-range level for field application rates. Finally, the HSAIMs were added to the treatments at a rate of 20 t.ha'1.

[0052] All treatments were mixed thoroughly and then wetted up to saturation (glistening appearance on soil surfaces). They were incubated at 25 °C in a temperature-controlled laboratory with no coverings so that they were able to pass through a drying cycle. Each week the treatments were returned to saturation point so that they were subjected to constant wetting / drying cycles to simulate field conditions. On three occasions after re- saturation, the treatments were placed into a 35 °C drying oven for 2 days in order to accelerate microbial activity during the trial period. After three months the trial was terminated and the treatments were again thoroughly mixed in preparation for laboratory testing.

[0053] Physical and chemical analysis

[0054] Moisture content for the soils, organic amendments and the minerals was estimated by measuring mass loss from the materials on oven-drying at 105 °C for 24 hours. The surface area of the soils was estimated using the Brunauer-Emmett-Teller (BET) method, measuring the amount of nitrogen gas sorption onto the materials.

[0055] Volumetric particle size distribution for the two soil types (both in triplicate) was determined by laser refraction using a Mastersizer 3000 instrument (Malvern Instruments, UK). Organic matter (OM) was determined for all starting materials, as well as samples from each treatment collected at the trial’s conclusion, by the Loss on Ignition method, whereby 5 g of dried-material is placed into a furnace at 550 °C for 4 hours.

[0056] Total carbon, total nitrogen and organic carbon (Corg) were measured on all starting materials and post-trial treatment samples following the Dumas combustion method using a LECO furnace. pH and EC were measured on all post-trial treatment samples following 1:5 soil: solution mixing ratios in deionised water, shaking for 1 hour and subsequent reading using a glass electrode (Hana Instruments).Material properties

[0057] The Vertisol was more microbially active than the Arenosol, as evidenced by its greater OM and total C content and slightly lower C / N ratio compared with the Arenosol (see Table 1 below) as well as its greater proportion of fine particles (see Figure 1). Corg concentrations comprised >90% of total C concentrations for both soils (as well as the organic amendments, as expected) indicating that inorganic carbonate carbon played a minor role in the carbon cycling processes in the trial.

[0058] Carbon concentrations, OM contents and C / N ratios were higher in the peat moss than in the cow manure, reflective of the peat moss presenting a more readily available pool of carbon than the composted and more microbially-mature cow manure (see Table 1 below).Table 1: Physicochemical properties of soil, organic and mineral components0059]nGravimetric Moisture ContentThe high surface area minerals all displayed higher specific surface areas than the Arenosol (see Table 1 above). However, the Vertisol was found to have higher specific surface area than the HSAIM, apart from MZ2. The high surface area of the Vertisol is likely reflective of the additive contributions of its mineralogy (clays) as well as refractory organic compounds.

[0060] Carbon and organic matter retention trends and processes

[0061] At the conclusion of the three-month incubation period, the treatments had lost approximately half of their starting C contents - of which between 73% and 91% was contributed by the organic amendments with the remainder being present in the initial soil. For the controls (i.e., soils and organic amendments only with no HSAIMs), Corg loss was greater for the peat moss amendments (57%) than the cow manure amendments (35%), reflecting a more readily digestible character of the peat moss. Corg loss was greater in the Arenosol (52%) thanthe Vertisol (39%) suggesting that the Vertisol inherently contains more carbon protecting HSAIMs than the Arenosol, which is supported by the particle size data (see Figure 1).

[0062] Modelled results for Corg concentrations for all post-trial treatments are shown in Figure 2. Figure 2 reports high (maximum)-low (minimum)-close (mean) plots for calculated Corg content for treatments at the end of the trial. Ctrl = soil+OM source (no mineral), MZ1 = manufactured zeolite 1, MZ2 = manufactured zeolite 2, NZ = natural zeolite, B = bentonite. N=4 for each treatment, *denotes values that are significantly different (p<0.05) from control.

[0063] As can be seen, mean Corg concentrations were higher in the Vertisol treatments than the Arenosol treatments, reflecting the higher initial Corg content of the Vertisol by a magnitude of approximately 3 -fold.

[0064] HSAIMs added to the Arenosol treatments amended with peat moss displayed lower mean Corg values relative to the controls (Arenosol+Peat Moss), albeit none significantly so. For the remaining 12 treatment combinations, HSAIM addition resulted in higher mean Corg concentrations relative to controls, with the synthetic zeolites generally providing the best performance, with the results being of statistically significant improvement over the control samples.

[0065] The proportion of carbon ‘protected’ by the HSAIMs was estimated using a mass balance approach: CP = { [CHT-CF] / [Ci-Cp] } xlOO, where CP is carbon protection expressed as a percentage, CHT is the Corg concentration of the HSAIM treatment measured at the trial’s conclusion, CF is the Corg concentration of the control treatment (i.e., soil and organic amendment only, with no HSAIM added) at the trial’s conclusion and Ci is the initial Corg content of the treatments.

[0066] The carbon balance estimates were calculated for only the eight HSAIM treatments that exhibited significantly higher predicted Corg concentrations than the controls. The results are shown in Figure 3. Figure 3 shows the calculated carbon protection for treatments that showed significantly higher predicted Corg concentrations relative to controls. HSAIM abbreviations: MZ1 = manufactured zeolite 1, MZ2 = manufactured zeolite 2, NZ = natural zeolite, B = bentonite. N=4 for each treatment. Upper and lower bars are standard errors of the mean.

[0067] All of the HSAIMs offered substantial carbon protection for at least one of the soil / organic matter treatment combinations. The manufactured zeolites were particularly effective, achieving carbon protection across the widest range of treatment combinations and exhibiting the maximum carbon protection of 25% (Type A zeolite).Figure 4 shows C / N ratio signatures for the four treatment combinations. The Arenosol+peat moss+HSAIM treatments at the trials conclusion all displayed C / N ratio signatures trending away from the pure soil signature, and towards the signature of the peat moss (see Figure 4A). The fact that these signatures trended away from their initial C / N ratios and towards the peat moss signature means that the microbial communities in these treatments must have been drawing down on the soil’s existing N reserves to process the added organic source. In other words, they were strongly N-limited. By contrast, the other three treatment combinations showed signatures trending in the reverse direction, i.e., away from the organic amendment and towards the pure soil (see Figure 4 B, C and D). The microbial communities in these treatments were not N limited. These results highlight possible risk in adding carbon-rich sources to N- limited soils, in which case it may be beneficial to provide a source of bioavailable nitrogen with the synthetic zeolite. The presence of nitrogen, and other bioavailable compounds, such as phosphorous and potassium not only supports plant growth, but also supports soil microbes in carbon cycling and offers better prospects for improved soil carbon sequestration.

[0068] OM contents of all treatments are shown in Figure 5. Figure 5 reports high (maximum)- low (minimum)-close (mean) plots for organic matter contents for treatments at the end of the trial. Ctrl = soil+OM source (no mineral), MZ1 = manufactured zeolite 1, MZ2 = manufactured zeolite 2, NZ = natural zeolite, B = bentonite. N=4 for each treatment, *denotes values that are significantly different (p<0.05) from control. The HSAIM treatment combinations generally resulted in significantly higher OM contents relative to the controls, with the synthetic zeolites being more effective in retaining OM.

[0069] Conclusion

[0070] Four types of high surface area inorganic minerals (HSAIMs) - two manufactured zeolites, one natural zeolite and bentonite - added to soil+organic matter amendments showed promise in protecting soil carbon in a laboratory trial.

[0071] Estimating carbon balances using predicted organic carbon data modelled from raw organic carbon and organic matter measurements, in conjunction with a range of other simple - to-measure soil properties overcame problems associated with using raw organic carbon readings (i.e., high sample variance).

[0072] Carbon protection maximized for the manufactured zeolites, and in particular for zeolite Type A at 25% over the 3 -month trial.

[0073] Soil type and organic amendment carbon content had a strong effect on protection efficiency - high carbon content organic inputs into N-limited soil resulted in a decrease in mean carbon levels retained (albeit not significantly).

[0074] It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

Claims

CLAIMS1. A method comprising applying a synthetic zeolite to soil.

2. The method of claim 1, wherein applying the synthetic zeolite to soil comprises applying the synthetic zeolite to soil over an area in an amount of from about 0.5 t.ha'1(0.05 kg.m'2) up to about 20 tha'1(2 kg.m'2).

3. The method of claim 2, wherein the amount is from about 1 t.ha'1(0.1 kg.m'2) up to about 10 t.ha'1(1 kg.m'2).

4. The method of any one of the preceding claims wherein the synthetic zeolite is a Type A zeolite or a Type X zeolite.

5. The method of any one of the preceding claims, wherein the synthetic zeolite is in the form of pellets or particles having a Dso of 5 mm or less.

6. The method of any one of the preceding claims, wherein the synthetic zeolite has a surface area of at least 100 m2 / g.

7. The method of any one of the preceding claims, wherein the step of applying the synthetic zeolite to the soil comprises applying a composition comprising the synthetic zeolite to the soil, the composition further comprising a source of bioavailable nitrogen.

8. The method of claim 7, wherein the compositions further comprises a source of bioavailable phosphorous and / or bioavailable potassium.

9. The method of claim 5, wherein the synthetic zeolite is in the form of pellets.

10. The method of claim 9, wherein the pellets further comprise a binder.

11. The method of claims 9 or 10, wherein the pellets further comprise a source of bioavailable phosphorous and / or bioavailable potassium.

12. The method of any one of claims 9 to 11 wherein the synthetic zeolite has a primary Dso particle size of 300 pm or less.

13. The method of any one of the preceding claims, wherein the zeolite comprises pores, and at least 65% of the pores have a pore diameter of about 4A ± 10%.

14. A soil treatment composition comprising a synthetic zeolite and a source of bioavailable nitrogen.

15. The soil treatment composition of claim 14, wherein the zeolite and the source of bioavailable nitrogen are in the form of pellets with a Dso of 5 mm or less.

16. The soil treatment composition of claim 15, wherein the pellets further comprise a binder.

17. The soil treatment composition of any one of claims 15 to 16, wherein the soil treatment composition further comprises a source of bioavailable phosphorous and / or bioavailable potassium.

18. The soil treatment composition of any one of claims 14 to 17, wherein the synthetic zeolite has a surface area of at least 100 m2 / g.

19. The soil treatment composition of any one of claims 14 to 17 wherein the synthetic zeolite has a primary Dso particle size of 300 pm or less.

20. The soil treatment composition of any one of claims 14 to 19 wherein the zeolite comprises pores, and at least 65% of the pores have a pore diameter of about 4 A + 10%.

21. Use of a soil treatment composition according to any one of claims 14 to 20 to treat soil for the protection of carbon therein.

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