Patent Description:
It is known to test soils to assess the carbon content of soils by the use of a Loss on Ignition test (LOI). In such a test, a sample of soil is strongly heated which causes volatile substances in the sample to escape until the mass of the sample ceases to change. The difference in weight before and after the ignition test represents the amount of organic material that was present in the sample. The organic carbon content in the soil can then be estimated from this weight change, the organic carbon content being in a known percentage range of organic material in the sample.

In my International Patent Application No, <CIT>. I disclose a method of and apparatus for obtaining an estimation of the organic carbon content of soil and/or variations or changes in organic carbon content of soil over time which uses a Loss on Ignition technique. In that method, one or more samples of soil are supported on gas permeable barriers arranged within an elongated hollow chamber after which a heated gas is supplied to the housing for passage through the soil sample/s to initially remove moisture form the samples to dry the soil samples and thereafter to remove burn off organic materials including organic carbon in the soil sample or samples, with the change of weight of the soil sample/s due to the heating process correlating to the organic carbon content in the soil sample, to be obtained. After a selected period of time subsequent further samples of soil can be taken from the same area and tested as above so that increases in organic carbon content which is equivalent to increases in carbon dioxide sequestration in the soil can serve as a basis for remuneration in a program which rewards carbon dioxide sequestration.

In the method and apparatus disclosed in the aforesaid International patent application a small quantity of soil particles can be forced through the gas permeable means before organic carbon is burnt off which results in small inaccuracies in calculation of the change of weight of the soil samples and thus in the calculation of changes in soil carbon content. It would desirable to have a method and apparatus in which these inaccuracies can be at least substantially eliminated.

Further in both the conventional Loss on Ignition method as well as the method disclosed in my aforesaid International patent application, inaccuracies can arise with certain types of soil. For example, if a soil has high iron content, the heating process may cause a reaction in the soil so that the measured change of weight in the soil before and after the heating process does not provide a true indication of the organic carbon content in the soil. In iron rich soils, for example, the change of weight in the soil sample may indicate that the soil has less organic carbon content that it actually has.

In addition, burning off of the organic carbon in the soil samples involves high temperatures, typically in the region of <NUM> and above. These temperatures cause the apparatus to heat considerably and as the oven is insulated so as to reach the high temperatures required, it takes considerable time for the oven and other parts of the apparatus to cool. This then delays a second and subsequent use of the apparatus because an extended period of time is required before the apparatus can again safely be used. It would be desirable to have a method and means for cooling the apparatus as quickly as possible for efficiency of operation, safety and other purposes.

A method not covered by the claimed invention of validating a test for estimating the organic carbon content of soil or changes in organic carbon content of said soil over time is provided, in which a first sample of said soil is taken from a selected location and heated using Loss On Ignition (LOI) to remove organic materials including organic carbon from said soil sample by burning off or oxidising said organic materials, said method comprising the steps of taking at least one further sample of soil from a location immediately adjacent to, and having the same geological structure as said selected location, said sample having or being treated to have minimal organic material content, adding to said further sample, a predetermined quantity of an organic material to provide a second sample, heating said second sample containing said quantity of organic material using Loss On Ignition (LOI) to burn off said quantity of organic material, and monitoring the change of weight of said second sample due to the burning off of said organic materials.

The change of weight in the second sample should be equal to the weight of the organic material added to the soil sample in which case the test is validated and no correction to the results is necessary. Should the weights not match, a reaction between the added organic material and inert material is indicated which means a correction is required to be made to the result.

The organic material added to the soil sample may be any organic material however a preferred organic material for use in the method comprises peat. The initial soil sample after initial heating is inert so that any subsequent measured change of weight of the second sample including the added organic material is due solely to the added organic material.

The method referred to above uses a loss on ignition (LOI) principle in which a sample of material is strongly heated which causes volatile substances in the sample to escape until the mass of the sample ceases to change. In the present invention, heating of the first soil sample and subsequent heating of the second sample is achieved by passing heated air or gas through the samples for a sufficient time and at selected temperatures until the weight of the samples ceases to change, the loss of weight being due to organic material including organic carbon being burnt off and oxidised. Preferably, the gas flow through the samples is controlled to control the temperature of the samples to ensure that the temperature thereof does not exceed a predetermined temperature or range of temperatures. Controlling the gas flow through the samples of soil controls oxygen flow through the samples and therefore controls the burning of materials in the samples and ensures that the temperature of the samples does not exceed the predetermined temperature or range of temperatures.

The validation method may be used in any Loss on Ignition testing process however it is preferred that the method be undertaken with apparatus of the type disclosed in my <CIT> ( Application No <CIT>). That apparatus comprises an housing defining an upright elongated chamber, gas permeable means for supporting one or more samples of said soil within said chamber, means for forcing heated gas downwardly through said chamber and the soil sample or samples therein to initially remove moisture from the soil sample or samples to dry said sample or samples and subsequently remove by burning off or oxidising organic materials including carbon from the soil sample or samples and means for measuring the change of weight of said soil sample or samples due to said removal of said organic materials to provide an indication of organic carbon content of the soil or changes in the organic carbon content of the soil. When applied to the validation of the test, organic material of known weight is added to the soil sample or samples after the above heating and organic material removal process and the procedure repeated.

Preferably, a plurality of soil samples are used and the soil samples are arranged within the chamber in series such that heated gas can be passed through the respective soil samples in turn. Preferably the housing and thus chamber have a central longitudinal axis with an inlet at one end for heated gas and an outlet at the other end. Preferably respective soil samples are arranged longitudinally along the axis of the chamber. Preferably the housing is of a tubular configuration and thus the chamber is of a circular cross section.

Preferably respective gas permeable means are provided to support the one or more soil samples within the chamber. Suitably the gas permeable means form barriers which extend diametrically of the chamber. The gas permeable means may comprise a soil sample holder which includes a grid or grating.

Means are suitably provided for weighing the housing containing the soil sample/s before and after the organic materials/carbon removal process to enable calculation of the change of weight in the soil sample/s whilst they remain in situ within the housing to provide an indication of organic carbon content in the soil sample/s. The weighing means is also used in the validation method for weighing the soil sample and added organic material before and after the subsequent reheating process to enable the change of weight thereof to be determined. The change of weight should be equal to the weight of the organic material added to confirm the test as a valid test as the weight of the soil sample after the first heating process, being inert, should not change.

The weighing means may comprise a beam balance having a beam or lever which has a central fulcrum, means on one side of the fulcrum for supporting the housing and means on the opposite side of the fulcrum for carrying a variable counter or balance weight. The housing may be suspended from the beam on one side of the fulcrum such as by means of a knife edge suspension. Preferably, the housing includes one or more hanger members to enable the housing to be suspended via the knife-edge suspension from the beam. Preferably the housing remains connected to the beam during the heating and oxidation process such that at the end of that process, the balance beam can be used for determining the total change in weight of the housing including the soil samples without the need to remove the soil samples from the housing.

Most preferably, the samples are obtained using an auger, the auger being operated to a first depth at a particular location to extract materials to provide a first sample. Preferably, continued operation of the auger to depths below the first depth provide materials for the samples to be used for validation of the results as described further below.

Alternatively the samples can be obtained by using an auger for example of the type disclosed in my International Patent Application No <CIT>. Such an auger may be operated to a first depth at a particular location to extract materials to provide a first sample. Subsequently, by continuing operating the auger downwards, after first removing all the above materials to provide the first sample, into the subsoil where negligible soil organic matter can be expected to provide a second sample.

If the test using the base which has been subject the LOI shows a greater LOI loss than predicted then a chemical reaction must have happened between (probably) the carbon in the organic matter and the already "cooked", and therefore, supposedly, inert sample material. Thus an adjustment of the results of the test on the first sample will need to be made to obtain the correct organic carbon content of the sample. If the LOI testing of the base which has not been subject to a LOI test before the peat has been added is then subject to a LOI test, that test will show a LOI weight loss which can be considered to be the same as would result from a test on a nearby soil which has a weight of organic matter content exactly the same as the weight of peat added to the subsoil material. For more accurate results, a series of Loss on Ignition (LOI) tests can be carried out using the subsoil material which contains no organic matter or little organic matter to which is added a different but known quantity of organic matter. By taking a series of tests a graph can then be drawn which plots the tested by Loss on Ignition (LOI) weights against the known weight of organic matter added to each sample. This graph can be used to show that when any future sample, taken from the same general location is subjected to a Loss On Ignition test the Loss on Ignition weight thus determined can be applied to the graph and the true organic matter content of the soil can be seen and carbon content determined.

Preferably soil particles forced through or past said gas permeable means are collected, and the change of weight of the soil samples adjusted for the weight of said collected soil particles provides an indication of the organic carbon content in the soil sample.

The present invention provides an apparatus for obtaining an indication of the carbon content of soil and/or variations of the carbon content in soil in accordance with the above described method, the apparatus comprising an upright housing defining a chamber, a soil sample holder for supporting one or more samples of said soil within the chamber, mean for forcing heated gas through said chamber and the soil sample or samples therein to remove organic carbon from the soil, means for collecting soil particles forced through of past the soil sample holder and means for measuring the change of weight of said soil sample or samples adjusted for the weight of said collected soil particles to provide an indication of carbon content in the soil.

Preferably, the housing is received coaxially within an outer tubular housing such that the walls of the respective housings are juxtaposed, the outer tubular housing being arranged within an outer casing and being surrounded by an insulating material.

The particle collection means is preferably located within a chamber vertically beneath the housings and the outer housing or an extended portion thereof extends into the chamber.

The particle collection means preferably is in the form of a tray which is slidably movable within the chamber. The chamber suitably is defined by a horizontally extending duct and the lower portion of the outer housing extends into the duct. Preferably, the horizontally extending duct is joined at one end to a vertically extending duct which acts as a stack or chimney for discharge of hot air or gases from the apparatus.

Preferably the opposite end of the horizontally extending duct is open and the collection means includes a face member so as to be in the configuration of a drawer wherein when the collection means is slid in a first direction the facing member can overlie and close the duct opening and wherein when the collection means is slid in an opposite direction, said face member moves away from and opens the opening,.

Preferably when the opening is open, air forced into the apparatus cools the apparatus and when flowing through the stack, induces a back pressure which will induce a further flow of air into the apparatus through the opened duct.

Preferably means are provided for creating a forced flow or air through the exhaust duct. Such means suitably comprises a fan, blower or other forced air source and means for connecting the fan, blower or forced air source to the interior of the exhaust duct. Preferably the connecting means comprises a pipe which extends from the blower or fan into the duct. The pipe suitably is in the form of an elbow having a first leg connected of the fan or blower and a second leg which extends longitudinally of the duct so as to direct air from the fan or blower towards the outlet of the duct.

The housing suitably is weighed before and after the organic carbon removal process. The change of weight should be equal to the weight of the organic material added to confirm the test as a valid test as the weight of the soil sample after the first heating process, being inert, should not change and cannot change when additional organic matter is added prior any heating.

Preferably, an annular space is defined between the housings through which cooling air may pass for cooling of the apparatus. Suitably the inner housing includes an annular flange which normally seats on the upper edge of the outer housing and for cooling purposes, the inner housing may be raised to move the flange away from the upper edge of the outer housing to define an opening therebetween to thereby open the annular space to the external atmosphere such that the back pressure will cause cooling air to flow into the annular space through the opening defined by the flange and upper edge of the outer housing. Means for supplying a cooling liquid such as a spray from a nozzle may be provided adjacent the opening such that cooling water may also be introduced into annular space for cooling.

In order that the invention may be more readily understood and be clear enough and complete enough for it to be performed by a person skilled in the art, reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein.

Referring to the drawings and firstly to <FIG> and <FIG>, there is illustrated apparatus <NUM> for use in heating a sample or samples of soil to remove organic carbon therefrom for the purpose obtaining an indication of the carbon content of the soil sample and for validating results obtained. The apparatus <NUM> comprises an oven <NUM> having an outer hollow casing <NUM> which typically is provided with legs <NUM> at its lower end whereby the casing <NUM> may be supported on an underlying surface. Adapted to be supported substantially within the casing <NUM> is a heating chamber <NUM> (see also <FIG>) for use in heating a sample or samples of soil for the purpose of burning off of organic carbon in the soil samples for subsequent assessment of the carbon content of the soil sample and thus the soil from which the sample was taken. The heating chamber <NUM> is of substantially the same or similar configuration as the heating chamber described in my aforesaid International Patent Application /<NUM>.

The heating chamber <NUM> comprises a main fixed outer elongated tubular housing <NUM> which is of a circular cross section and which has an flange <NUM> adjacent its upper end for seating on an upper surface or wall <NUM> of the casing <NUM> as shown in <FIG> so that the housing <NUM> is supported in an upright attitude. The housing <NUM> extends a small distance above the flange <NUM> as at <NUM>' and is open at its upper end to receive coaxially therein with clearance an inner tubular housing <NUM>. The housing <NUM> has an annular flange <NUM> adjacent its upper end which may seat on the upper end of the extended portion <NUM>' of the housing <NUM>. The upper end of the housing <NUM> is open at <NUM> to accept therein a primary air or gas heater <NUM> and sample holder <NUM> which is interconnected with the heater <NUM> and located on the lower side thereof. The heater <NUM> and holder <NUM> may be withdrawn from or inserted into the upper open end <NUM> of the housing <NUM>. An insulating material <NUM> is provided in the casing <NUM> to surround the outer housing <NUM>. The insulating material <NUM> may be rock wool or any other suitable material or combination of insulating materials.

Provided at the lower end of the housing <NUM> is a secondary heating element <NUM> which is wound around the housing <NUM>. The primary gas heater <NUM> includes an elongated hollow housing <NUM> which can be inserted into and received substantially coaxially within the tubular member <NUM>. The housing <NUM> also has an annular flange or collar <NUM> which can seat on the projecting upper end <NUM>' of the member <NUM> and be sealed thereto by an O-ring seal <NUM> provided on or in an internal annular recess in the flange <NUM>. When the annular flange or collar <NUM> is in position over the upper end of the housing as shown in <FIG>, the seal <NUM> seals the collar <NUM> to the outer surface of the tubular member <NUM>. The primary heater <NUM> includes a series of coaxially arranged tubular members <NUM> and a heating wire or element <NUM> wound around the tubular members <NUM>. The top of the housing <NUM> is provided with a connector <NUM> for connection to a compressed gas or air source such as a compressor via a suitable control valve. The housing <NUM> also carries terminals <NUM> for connecting the heater wire or element <NUM> to a source of power.

In use when compressed gas such as compressed air is supplied from the compressed air or gas source to the inlet connector <NUM> and current is supplied to the heating element <NUM>, air passes as indicated by the arrows in <FIG> in a serpentine manner between the tubes <NUM> and past the heating element <NUM> to exit at <NUM> at the lower end of the heating unit <NUM>.

The housing <NUM> suitably at the collar <NUM> also includes diametrically arranged connectors <NUM> which can connect to the flange <NUM> so that housing <NUM> and tubular member <NUM> can be interconnected for a purpose described further below. The connectors <NUM> each include a threaded rod <NUM> having a head or nut <NUM> at one end and the flange <NUM> (or a bracket attached to the flange <NUM>) has a slot which can receive the rod <NUM> therethrough and act as a stop with the head <NUM>. The respective threaded rods <NUM> are also threadedly engaged with internally threaded lug <NUM> arranged on diametrically opposite sides on the collar <NUM> and hand actuated lock nuts <NUM> are engaged with the rod <NUM>.

The soil sample holder <NUM> includes a series of soil sample holding units <NUM> which are arranged in use in spaced apart positions along a central shaft <NUM> which is secured at its upper end to the heating unit <NUM>. Each soil sample holding unit <NUM> is of the same configuration as that disclosed in Figs <NUM> and <NUM> of my aforesaid International Patent Application PCT/<CIT> including as shown in <FIG> and <FIG>, a rigid holder <NUM> comprising an air or gas permeable grid or mesh member <NUM> of a diameter similar to the internal diameter of the tubular member <NUM>. The holders <NUM> may be fixed to the shaft <NUM> or may be adjustable along the shaft <NUM> and fixed at various positions along the shaft <NUM>.

To prevent or minimize escape of fine soil particles, the soil sample holding unit <NUM> may be used with a flexible cup shaped member <NUM> formed of a fabric or other pliable material which is air or gas permeable which can seat on the grid or mesh member <NUM>. The fabric or other pliable material preferably comprises an air or gas permeable material which can handle the temperatures encountered in the apparatus <NUM>. A suitable material may comprise a woven fibreglass cloth. The gas permeable member <NUM> may be formed or shaped from material which is initially in a flat form which can be folded into a generally cup-shaped configuration. The cup shaped member <NUM> is also provided with a central opening <NUM> which can neatly but firmly receive the shaft <NUM> and substantially seal thereagainst.

The lower end of the housing <NUM> extends through the base <NUM> of the outer casing <NUM> as at <NUM> and a collection means <NUM> which comprises a tray <NUM> can be moved to a position directly below the extended lower end of the housing <NUM> as shown in <FIG>. This enables any particles of soil or other materials in samples held on the sample holder <NUM> which is forced through or past the grid <NUM> and permeable fabric <NUM> supported on the grid <NUM> collect on the tray <NUM>. These materials can then be weighed and adjustments then can be made to the initial weight of the soil samples as described below.

The collection tray <NUM> is located within a chamber <NUM> which is defined by one leg <NUM> of an exhaust duct <NUM> which is located and suspended in a horizontal attitude beneath the casing <NUM>. The leg <NUM> of the duct <NUM> is connected at the rear of the casing <NUM> to, and communicates with, an upright leg <NUM> of the duct <NUM> which is open at its upper end <NUM> and which serves as a chimney or vent to direct hot gases upwardly away from the casing <NUM>.

As shown also in <FIG> and <FIG>, the leg <NUM> of the duct <NUM> extends forwardly to terminate at a position <NUM> in substantial alignment with the front wall of the casing <NUM>. A bracket <NUM> which is an upwardly bent portion of the top flange of the duct leg <NUM> secures the leg <NUM> by the use of mechanical fasteners such as rivets to the front of the casing <NUM>. The collection tray <NUM> is of slightly less width than the internal width of the duct leg <NUM> and includes a planar base <NUM> which seats on the lower flange of the duct leg <NUM> so as to be supported for sliding movement thereon. The tray <NUM> additionally includes opposite upright side flanges <NUM> which serve to constrain materials deposit onto the tray <NUM>. Furthermore the tray <NUM> at its outer end is provided with an upright face member <NUM> so that the collection tray <NUM> is in somewhat of a drawer configuration. The face member <NUM> is peripherally larger than the cross section of the duct leg <NUM> such that when in the <FIG> position, the face member <NUM> overlies the opening <NUM> into the duct leg <NUM> to substantially close the opening <NUM> whilst in the <FIG> and dotted outline position of <FIG>, the collection tray <NUM> is slid outwardly of the duct leg <NUM> so that the face member <NUM> is moved clear of the opening <NUM> to open the outer end of the leg <NUM> to the external atmosphere.

The apparatus <NUM> also includes an upstanding mast <NUM> which extends parallel to the duct leg <NUM> and which is mounted at its lower end on an upright spigot <NUM> on the top wall <NUM> of casing <NUM> for rotation about its longitudinal axis. Brackets <NUM> support the mast <NUM> to the duct leg <NUM> and allow for this rotational motion. A handle <NUM> fixed to the lower end of the mast <NUM> can be grasped to enable the mast <NUM> to be pivoted by hand in opposite directions. At its upper end the mast <NUM> has an outwardly extending arm <NUM> which carries a winch <NUM> at its free end, the cable <NUM> of the winch <NUM> being connected to a lifting eye <NUM> on the housing <NUM> so that the primary heating unit <NUM> and soil sample holder <NUM> (and tubular housing <NUM>) can be raised or lowered. In addition, the mast <NUM> is provided with a radially outwardly extending support arm <NUM> which when rotated with or relative to the mast <NUM> can be moved to a position beneath respective sample holding units <NUM> so as to support the primary heating unit <NUM> and sample holder <NUM> whilst each holding unit <NUM> is being loaded with a soil sample.

For additional cooling of the apparatus <NUM> after its use and for rapid turnaround, a pipe <NUM> is provided for introducing a flow of air into the upright duct leg <NUM> as shown in <FIG> and <FIG>. The pipe <NUM> is in the form of an elbow having a first upright portion <NUM> and a second horizontal portion <NUM> which penetrates the wall of the duct leg <NUM> and which is connected to an air blower <NUM>. Alternately the portion <NUM> of the elbow <NUM> may be connected to a remote source of air such as a compressor.

For obtaining an indication of the changes of weight of the soil samples consequent of heating thereof, the apparatus <NUM> may incorporate a balance scale including a balance beam <NUM> (show in dotted outline in <FIG>, and in <FIG>) which has opposite parallel arms <NUM> which are supported at a knife-edge fulcrum <NUM> intermediate their ends defined by blades <NUM> supported on brackets <NUM> extending from one side of the casing <NUM>. For support of the heater <NUM> and soil sample holder <NUM>, brackets <NUM> on the annular flange <NUM> incorporate spaced apart hangers <NUM> for suspending the housing <NUM> and attached heater <NUM> and holder <NUM> in the manner described further below.

A variable counter- or balance weight <NUM> is supported to the arms <NUM> on the opposite side of the fulcrum <NUM> by means of a hanger/knife edge connection <NUM> similar to that for the housing <NUM>. The housing <NUM> and balance weight <NUM> are arranged at equispaced positions on opposite sides of the fulcrum <NUM> of the beam <NUM>. The counter weight <NUM> may include a beaker or container <NUM> to which a liquid such as water can be added or removed to balance the beam <NUM>. The counter or balance weight <NUM> can also include or comprise fixed or variable weights <NUM> (see <FIG>).

In use samples of soil <NUM> taken from an area where carbon content is to be assessed is screened to remove all fibrous material such as plant and animal material not yet decomposed and the soil samples are then placed within the respective holders <NUM> by operating the winch <NUM> to elevate the heater <NUM> and soil sample holder <NUM>, then lowering and filling each unit <NUM> in turn during which they are supported by the support arm <NUM> which can be pivoted between a non-supporting position and a supporting position. After the soil sample holder <NUM> has been inserted endwise into the upper end of the housing <NUM> the heater <NUM> follows being lowered so that it the housing <NUM> seals through the seal <NUM> to the upper end of the housing <NUM>. The collar <NUM> of the housing <NUM> may then be secured to the flange <NUM> by the threaded rod connectors <NUM>.

For heating of the soil samples, the housing <NUM> and attached housing <NUM> are suspended on the beam <NUM> are initially urged downwardly into the outer housing <NUM> until the flange <NUM> seats on the upper end <NUM>' of the housing <NUM> as shown in <FIG> and <FIG>. In this position as shown in <FIG>, the beam <NUM> will not be in balance and a weight may be applied to the housing end <NUM> of the beam <NUM> to maintain the unit in the position of <FIG> and <FIG>. In this position, the annular space <NUM> between the housings <NUM> and <NUM> will be closed or sealed at its upper end to prevent upward flow of air in this space. Current can then be applied to the heater element <NUM> and compressed air or gas supplied from the compressed air or gas *source via the connector <NUM>. Air will be forced through the heater <NUM> past the element <NUM> to be heated and exit at the lower end <NUM> of the heater <NUM> and the heated air will then be forced through the soil samples <NUM>. Initially the heating unit <NUM> is operated to remove moisture from the soil samples <NUM> to dry the soil sample/s <NUM>. When the sensed temperature increases above <NUM> which is the boiling point of water or moisture within the soil samples <NUM>, the soil samples <NUM> will be dry. The weight holding the apparatus <NUM> in the position of <FIG> and <FIG> is removed and weight may be applied to the counter weight <NUM> for example by adding liquid to the beaker <NUM> until the beam <NUM> is balanced for example as shown in <FIG>. This provides an indication of the weight of the soil samples <NUM> after the drying process and prior to the carbon removal process.

The beam <NUM> is then returned to the position of <FIG> in which the flange <NUM> of housing <NUM> seats on the upper end of the housing <NUM> and current applied to the heating element <NUM> and compressed gas supplied through the connection <NUM>. Typically the samples <NUM> are heated to temperatures above or in the region of <NUM> and maintained at those temperatures for an extended period of time for example <NUM> - <NUM> minutes to ensure that organic carbon and other organic materials are burnt off. This temperature and time however can be varied by varying current supply to the heater <NUM> and also by varying the air or gas supply. To ensure that the temperature of the soil samples does not increase beyond predetermined limits, gas flow through the samples may be restricted. This restricts the volume of oxygen supply to thereby prevent excessive burning of materials within the soil samples. The heating time and temperature of air or gas supplied may also be varied depending up the samples being tested. The balance beam <NUM> may then be released and balanced by adding liquid to the container. The weight of the added liquid corrected by taking into account losses due to the weight of materials collecting on the tray <NUM> will correlate to the organic carbon content in the soil samples.

To enable the test results to be validated, it is preferred for efficiency of operation that the apparatus <NUM> be cooled and for that purpose, the collection tray <NUM> is slid outwardly to the position of <FIG> and <FIG> which opens the opening <NUM> to the duct leg <NUM> to the external atmosphere. Compressed air is continued to be supplied through inlet <NUM> to flow through the housing <NUM> to cool the apparatus <NUM>, that air flowing downwardly into the legs <NUM> and <NUM> of the duct <NUM> whilst flow of air outwardly through upper end <NUM> of the duct leg <NUM> induces a back pressure in the duct leg <NUM> and causing air to be drawn from externally of the casing <NUM> into the opening <NUM>. This will result in enhanced cooling of the apparatus.

For additional or alternate cooling of the apparatus <NUM>, the blower <NUM> is operated to inject a flow of air through the elbow <NUM> into the duct leg <NUM> with air flowing upwardly as indicated by the arrows in <FIG>. At the same time or prior to operation of the blower <NUM>, the winch <NUM> is operated to raise the air heater <NUM>, connected sample hold <NUM> and inner tubular member <NUM> which is connected to the housing <NUM> through the threaded connectors <NUM>. This also causes the flange <NUM> which is provided adjacent to the upper end of the tubular member <NUM> to be raised above the upper edge <NUM>' of the tubular housing <NUM> as shown in <FIG>. This opens the annular space <NUM> between the tubular members <NUM> and <NUM> to the external atmosphere. Air supplied to the duct leg <NUM> creates a back pressure in the duct leg <NUM> and causing air to be drawn from externally of the apparatus <NUM> into the annular space <NUM> and downwardly through that space which will result in rapid cooling of the apparatus <NUM>. The collection tray <NUM> may also be slid open or partly open to the position shown in <FIG> and in dotted outline in <FIG> so that external air is drawn into the chamber <NUM> for further cooling of the apparatus <NUM>. Additional cooling can be achieved by the use of a water source such as a water spray nozzle <NUM> as shown in <FIG>. The spray nozzle <NUM> may be operated when the blower or fan <NUM> is operating and when the inner housing <NUM> is elevated as in <FIG> so that water is drawn into the annular space <NUM> within the tubular member <NUM>.

To validate the results of the above test, a sample of soil, say around one and a half kilograms, is extracted from an area immediately adjacent to, and having the same geological structure as, the region from where the soil sample being tested has been obtained. That sample is heated to remove all organic materials including organic carbon such as by the method and using the apparatus describe above (or by other means). The sample subsequent to its heating to remove organic materials can thus be weighed and used as an "inert base".

The soil samples may be extracted by using as shown in Fig. <NUM> a powered auger <NUM> operating in a tube <NUM> as for example of the type disclosed in my International Patent Application<CIT>. The auger <NUM> may be inserted into the ground and operated to a depth D1 so that all the soil within that depth is removed to provide the first sample for testing for organic carbon content. Continued operation of the auger <NUM> downwards to the additional depth D2 into the subsoil will provide a second sample for use in validating the test performed on the first sample. The second subsoil sample can be expected to contain negligible soil organic matter thus can be used as the zero organic matter content point from which both increases and levels of organic matter content can be determined.

If it is suspected that this sample from the D2 depth contains organic materials, a sub-sample from of this material can be heated in the apparatus described above to burn off any suspected organic materials so that it can be used as a truly organic matter free and inert base. It is noted that any material that is not organic matter, such as structural water can also be removed in this heating process.

Sub samples derived from either of the above methods are weighed after drying heating and removal from the oven <NUM> and to those base subsamples can be added some carefully weighed sample of (usually unavoidably moist) organic matter, typically peat. The samples of soil containing the added organic matter are subject to an additional re-drying and re-weighing from which the dry weight of the added organic matter or peat is determined then a Loss on Ignition (LOI) test, such as tests using the apparatus described above, and the loss of weight measured. If the loss in weight equals the weight of the added organic matter, the test of the first sample will be validated with the calculated carbon content thereof being correct.

If the test using the base which has been subject the LOI shows a greater LOI loss than predicted then a chemical reaction must have happened between (probably) the carbon in the organic matter and the already "cooked", and therefore, supposedly, inert sample material. This could, for example, show the presence of a hematite to magnetite reaction. Thus an adjustment of the results of the test on the first sample will need to be made to obtain the correct organic carbon content of the sample. This adjustment may be made on a pro-rata basis.

If the LOI testing of the base which has not been subject to a LOI test before the peat has been added is then subject to a LOI test, that test will show a LOI weight loss which can be considered to be the same as would result from a test of on a nearby soil which has a weight of organic matter content exactly the same as the weight of peat added to the subsoil material.

If different an adjustment may be made on a pro-rata basis however for more accurate results, a series of Loss on Ignition (LOI) tests can be carried out using the subsoil material which contains no organic matter or little organic matter to which is added a different but known quantity of organic matter. By taking a series of tests a graph, as shown in <FIG> can then be drawn which plots the tested by Loss on Ignition (LOI) weights against the known weight of organic matter added to each sample. This graph can be used to show that when any future sample, taken from the same general location is subjected to a Loss On Ignition test the Loss on Ignition weight thus determined can be applied to the graph and the true organic matter content of the soil can be seen and carbon content determined.

The validation procedures described above avoids the possible issue of an "organic matter chemical combination with the soil material" problem as can occur with the conversion of hematite to magnetite.

With most soil types, the quantity of organic matter determined can be used to accurately estimate the actual total weight of organic carbon in any nominated area of land and thus assist in estimating a national as is required in the Kyoto Protocol. However, determining the total weight is only of such academic interest as the prime concern is ending global warming, and therefore it is measuring specific increases in soil carbon and then being able to reward farmers for those increases.

It will be appreciated that the apparatus of the invention may be in many different configurations other than that illustrated and described to perform the method.

Whilst the method has been described where soil samples are heated by forcing hot air through the samples to dry the samples and/or remove carbon from the samples, the validation method may equally be applied to other Loss on Ignition (LOI) techniques used for determining the organic carbon content of a soil sample. Many different arrangements may also be used for the weighing of the soil sample or samples or apparatus or housing which contains the soil sample or samples other than the arrangement described in the embodiment.

Claim 1:
Apparatus (<NUM>) for performing a method wherein a first soil sample is taken from a selected location and heated using Loss On Ignition (LOI) to remove organic materials, and at least one further sample of soil is taken from a location immediately adjacent to and having the same geological structure as the selected location, the further sample having or being treated to have minimal organic material content, adding to the further sample a predetermined quantity of an organic material to provide a second soil sample, and heating the second soil sample using Loss on Ignition (LOI) to remove the quantity of organic material, the apparatus (<NUM>) comprising an upright housing (<NUM>) defining a chamber, a soil sample holder (<NUM>) comprising one or more gas permeable means (<NUM>) for supporting the first and/or second soil samples within the chamber, means (<NUM>) for forcing heated gas through the chamber and the soil sample or samples therein to remove organic materials including carbon from the soil, means (<NUM>) for collecting the soil particles forced through or past the soil sample holder (<NUM>), and means (<NUM>) for measuring the change of weight of the soil sample or samples adjusted for the weight of the collected soil particles to provide an indication or assessment of carbon content in the soil.