AU2003240312B2

AU2003240312B2 - A soil moisture sampling device and method

Info

Publication number: AU2003240312B2
Application number: AU2003240312A
Authority: AU
Inventors: Charles Julian Russell Baker
Original assignee: Bobtail Technologies Pty Ltd
Current assignee: Bobtail Technologies Pty Ltd
Priority date: 2002-06-27
Filing date: 2003-06-27
Publication date: 2007-10-25
Anticipated expiration: 2023-06-27
Also published as: AU2003240312A1

Description

WO 2004/003547 PCT/AU2003/000805

TITLE

"A SOIL MOISTURE SAMPLING DEVICE AND METHOD" FIELD OF THE INVENTION The present invention relates to a soil moisture sampling device and method.

BACKGROUND TO THE INVENTION It is known to require a means of determining properties of soil in which crops are grown. Properties of the soil such as pH and electrical conductivity require measurement in certain situations. In particular circumstances it may also be desirable to measure the concentration of particular salts within the soil. Additionally, it may be advantageous to determine the quantity of moisture leaching through the soil at a particular location.

A known type of measurement device used is an electronic device which measures soil conductivity. This device induces an electric field within the soil and measures the properties of this field.

Such a device is often electronically complex. In addition, there is not always a direct correlation between the soil conductivity and the level of nutrients available to a plant. Further, the device does not have the capacity to measure the volume of moisture passing through the soil.

WO 2004/003547 PCT/AU2003000805 The present invention attempts to overcome at least in part some of the aforementioned disadvantages of previous soil analysing devices.

SUMMARY OF THE INVENTION In accordance with a first aspect of the present invention there is provided a soil moisture collection device having an opening through which moisture can pass, a moisture collector arranged to receive moisture which has passed through the opening and a measuring means, characterised in that the measuring means measures a property of the moisture received in the moisture collector.

In accordance with a second aspect of the present invention there is provided a method of determining the properties of water in soil, the means comprising the steps of collecting water passing through a particular location in the soil and measuring the properties of the water collected.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic cross sectional view of a soil moisture sampling device in accordance with a first embodiment of the present invention; Figure 2 is a schematic cross sectional view of a soil moisture sampling device in accordance with a second embodiment of the present invention; and Figure 3 is a characteristic output graph of the soil moisture sampling device of Figure 2.

WO 2004/003547 PCT/AU2003/000805 3 DESCRIPTION OF THE INVENTION Referring to Figure 1, there is shown a soil moisture sampling device 10. The soil moisture sampling device 10 comprises a first container 12 and a second container 14.

Each of the containers 12, 14 is substantially frusto conical in shape, and comprises a substantially circular base 16 and a substantially frusto conical side wall 18 extending outwardly of the base 16. The containers 12, 14 are open at an outer end 20 thereof.

The first and second containers 12, 14 are arranged such that the second container 14 is inverted with respect to the first container 12, with the respective bases 16 being joined and coextensive.

The soil moisture sampling device 10 further includes a tube 22. The tube 22 extends from a first end 24 located, in use, above the outer end 20 of the first container 12 to a second end 26 located within the second container 14. The tube 22 thus passes through the joined bases 16 of the first and second containers 12, 14.

The tube 22 is closed at the second end 26 by suitable means such as a capping member 28. A moisture collector is thus defined within the tube adjacent the second end 26. The tube 22 is selectively open at the first end 24.

The tube 22 has a moisture inlet 29 and a moisture outlet 30. The moisture outlet 30 is comprised of an aperture in the tube 22 located adjacent the second end 26. The moisture inlet 29 is comprised of a small aperture located along the tube 22, at a location, in use, within the first container 12 and adjacent the base 16 thereof.

The moisture inlet 29 is surrounded by a filtering means 32. The filtering means 32 is located adjacent the base 16 of the first container 12, and surrounds the tube 22. The filtering means 32 may be comprised of a water permeable sponge.

WO 2004/003547 PCT/AU2003/000805 A measuring means 34 is arranged to be inserted in the tube 22 at the first end 24 and lowered to the second end 26. The measuring means 34 may be arranged to measure the pH, salt content, temperature or any other desired property of moisture contained within the moisture collection portion. A data transfer cable 36 extends from the measuring means 34 to a data collection device (not shown).

In use, the first container 12 is at least partially filled with a filter medium such as clean sand 36. The soil moisture sampling device 10 is then buried at a desired depth in the soil 38 to be tested. The soil moisture sampling device 10 is arranged such that the tube 22 is substantially vertical, with the first end 24 thereof being above the surface 40 of the soil 38 in which the device 10 is buried. The second container 14 is arranged to be substantially empty such that an air space 42 surrounds the second end 26 of the tube 12.

A portion of any nutrient containing water progressing under the action of gravity from the surface of the soil downwards through the soil will pass through the soil moisture sampling device 10. The water will pass initially through the filter medium in the first container 12, which will prevent any large particles contained in the water from passing therethrough. The water will then pass through the filtering means 32, which will act to prevent smaller particles from being transmitted. The filtered water will thus enter the moisture collector of the tube 26.

The measuring means 34 will measure the properties of the water passing through the soil. This information will be transmitted by the data transfer cable 36 to the data collection device. In this way a user will be able to determine the levels of nutrients WO 2004/003547 PCT/AU2003/000805 available to plants growing in the soil, and be able to apply fertilisers and the like accordingly.

Water collected in the moisture collector of the tube 22 will exit the tube via the moisture outlet 30. A flow measuring device (not shown) such as a tipping bucket gauge may be located in the air space 42 beneath the moisture outlet 30 so as to determine the volume of water and therefore the quantity of nutrients passing through the soil.

In a second embodiment of the present invention shown in Figure 2, the soil moisture sampling device 10 comprises a single container 50. The container 50 may be substantially cylindrical in shape as shown in the drawing of Figure 2, or any other suitable shape such as rectangular. The container 50 shown in the drawing has a substantially cylindrical side wall 18 and a substantially circular base 16. The base 16 includes apertures 52 through which water can pass. The container 50 is open at an upper end In a preferred embodiment of the invention the side wall 18 includes a plurality of inverted V-shaped apertures (not shown). The V-shaped apertures allow the ingress of plant roots within the container 50, whilst limiting the potential for water to flow through the side wall 18 by capillary action.

The soil moisture sampling device 10 includes a water impervious barrier 54. The water impervious barrier 54 is mounted to an interior wall 18 of the container 50 at a location approximately mid way between the base 16 and the upper end 20. The water impervious barrier 54 is substantially conical in shape, and is oriented with an apex 56 WO 2004/003547 PCT/AU2003/000805 6 pointed towards the base 16. The water impervious barrier 54 has an opening 58 at the apex 56 to allow water to pass through the water impervious barrier 54 at the opening 58.

The container 50 contains a layer of filtering medium 36, such as clean sand. In a preferred embodiment of the invention, the filtering medium 36 is river sand which has been screened below 1mm diameter. The filtering medium 36 is located above the water impermeable barrier 54.

A filtering means 32 is located, in use, immediately above the opening 58 of the water impermeable barrier 54. The filtering means 32 may comprise a stainless steel mesh, a felt filter, or any other suitable coarse filter material to prevent the filtering medium 36 from passing through the opening 58.

Preferably, the filtering means 32 is impregnated with a suitable herbicide such as trifluralin or pendamethalin in order to prevent plant roots from blocking the opening 58.

The container 50 includes an air space 42 located between the water impermeable barrier 54 and the base 16.

A water collector which incorporates a flow meter, such as a tipping bucket flow meter 60, is located in the air space 42 directly beneath the opening 58 in the water permeable barrier 54. The tipping bucket flow meter 60 includes at least one measuring means 34, located on a first side of the tipping bucket flow meter 60. The measuring means 34 is arranged to measure a desired property or properties of moisture collected in the first side of the tipping bucket flow meter 60. Preferably, the measuring means 34 is a electrical conductivity sensor.

WO 2004/003547 PCTAU2003/000805 The soil moisture sampling device 10 further includes water sampling collectors 62 associated with each side of the tipping bucket flow meter 50. The water sampling collectors 62 receive water which overflows from the tipping bucket flow meter 50. A sampling tube 64 extends from each water sampling collector 62 to the surface In use, the soil sampling device 10 is buried in the soil 38 at a desired location beneath the surface 40. The container 50 is arranged such that soil 38 extends from the upper end 20 of the container 50 to the layer of filtering medium 36. The distance between the upper end 20 of the container 50 and the layer of filtering medium 36 is sufficient to prevent water being drawn away from the container 50 by capillary action within the soil 38. Where the soil 38 is relatively coarse this distance will be small. Where soil 38 is heavy, such as in the case of clay, the distance will be relatively large.

In order to further break capillary action, the filter medium 36 may be graduated in particle size. In this embodiment the filter medium 36 will have a particle size similar to that of the soil 38 adjacent the soil 38, gradually reducing to a required filter size adjacent the filtering means 32.

In use, water passing downwards through the soil 38 in the region above the container 38 passes through the soil 38 and the filter medium 36 to the water impermeable barrier 54. It then flows along the barrier 54, passing through the filter means 32, and through the opening 58 into the tipping bucket flow meter Desired properties of the water are then measured by the measuring means 34. In a preferred embodiment of the invention, data is transferred from the measuring means 34 to a data collection device (not shown) on the surface. Where the measuring means 34 is an electrical conductivity sensor, the conductivity (in mS/cm) of the water in the WO 2004/003547 PCT/AU2003/000805 side of the tipping bucket flow meter 60 containing the measuring means 34 can be graphed against time (marked in two minute increments). An example of such a graph is shown in Figure 3.

The graph will have a characteristic appearance of successive periods of positive conductivity and zero conductivity. Each period represents a tip of the tipping bucket flow meter 60. Analysis of the graph will thus reveal the frequency of bucket tips, showing the flow rate of water through the soil 38, and the conductivity of that water, representing the amount of dissolved salts such as nutrients in the soil. This arrangement avoids the needs for the use of micro switches to monitor movements of the tipping bucket flow meter 60. It will be appreciated that other means of recording tips of the tipping bucket flow meters, such as micro switches or magnetic switches, may also be employed. It may also be desirable in some applications for measuring means 34 to be used in both sides of the tipping bucket flow meter.

Should further sampling or measurement of the water be required, samples can be drawn from the water sampling collectors 62 through the water sampling tubes 64.

Additionally, further measuring 34 means can be placed within the water sampling collectors 62.

Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

Claims

1. A soil moisture collection device having an opening through which moisture can pass, a moisture collector arranged to receive moisture which has passed through the opening and a measuring means, characterised in that the measuring means measures a property of the moisture received in the moisture collector.

2. A soil moisture collecting device as claimed in Claim 1, characterised in that the measuring means measures the salts content of the moisture.

3. A soil moisture collection device as claimed in Claim 2, characterised in that the measuring means measures the electrical conductivity of the moisture.

4. A soil moisture collection device as claimed in any one of the above claims, characterised in that the measuring means measures the pH of the moisture.

A soil moisture collection device as claimed in any one of the above claims characterised in that the moisture collector includes a flow meter.

6. A soil moisture device as claimed in Claim 5 characterised in that the moisture collector is a tipping bucket flow meter.

7. A soil moisture collection device as claimed in claim 6 characterised in that the measuring means is located on one side of the tipping bucket flow meter. WO 2004/003547 PCT/AU2003/000805

8. A soil moisture collection device as claimed in Claim 6 characterised in that the tipping bucket flow meter has a measuring means associated with each side.

9. A soil moisture collection device as claimed in any one of Claims 5 to 8 characterised in that the soil moisture collection device includes a water sampling collector arranged to receive moisture from the flow meter.

A soil moisture collection device as claimed in any one of Claims 1 to 4 characterised in that the soil moisture collection device includes a flow meter arranged to receive water from the water collector.

11. A soil moisture collection device as claimed in any one of the preceding claims characterised in that the soil moisture collection device includes a filtering medium between the opening and the moisture collector.

12. A soil moisture collection device as claimed in Claim 11 characterised in that the filtering medium is sand.

13. A soil moisture collection device as claimed in Claim 12 characterised in that the filtering medium is sand having a diameter less than about 1mm.

14. A soil moisture collection device as claimed in Claim 12 characterised in that the sand is graduated in particle size so that sand closer to the opening is coarser than sand closer to the water collector.

WO 2004/003547 PCT/AU2003/000805 11 A soil moisture collection device as claimed in any one of Claims 11 to 14 characterised in that the soil moisture collection device includes a filtering means located between the filtering medium and the moisture collector

16. A soil moisture collection device is claimed in Claim 15 characterised in that the filtering means is a mesh.

17. A soil moisture collection device as claimed in Claim 15 or Claim 16 characterised in that the filtering means is impregnated with a herbicide.

18. A soil moisture collection device as claimed in any one of the above claims characterised in that soil is received in the opening.

19. A soil moisture collection device as claimed in any one of the above claims characterised in that the soil moisture collection device has a side wall,'the side wall includes a plurality of holes.

A soil moisture collection device as claimed in Claim 19 characterised in that the holes are inverted-V shaped.

21. A method of determining the properties of water in soil, the means comprising the steps of collecting water passing through a particular location in the soil and measuring the properties of the water collected. WO 2004/003547 PCT/AU2003/000805 12

22. A method of determining the properties of water in soil as claimed in Claim 21, the method including the step of measuring the electrical conductivity of the water collected

23. A method of determining the properties of water in soil as claimed in Claim 21 or Claim 22 characterised in that the water is collected in a tipping bucket flow meter.

24. A method of determining the properties of water in soil as claimed in Claim 23 characterised in that tips of the tipping bucket flow meter are indicated by a change in the properties being measured.