Abstract:
A soil moisture sampling device ( 10 ) arranged to be beneath a workable crop soil surface for measuring the properties of soil moisture. The soil moisture sampling device comprises a moisture collector device ( 12 ) and an instrument enclosure ( 14 ). The instrument enclosure ( 14 ) contains a tipping bucket ( 38 ) arranged to receive water from a tube ( 24 ). The tube ( 24 ) contains measuring means ( 34 ) and the tipping bucket ( 38 ) contains magnet means ( 40 ). The arrangement enables water volume to be measured by the bucket ( 38 ) tipping when one portion ( 44  or  46 ) is full.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a soil moisture sampling device. 
       BACKGROUND TO THE INVENTION 
       [0002]    It is known to use a set of lysimeters to monitor the quantity of water flowing through soil and to measure features of this water such as the amount of dissolved fertilizers contained therein. An apparatus and method for achieving this are described in the applicant&#39;s prior Australian Patent Application Number 20032403 12. 
         [0003]    It has since been found that the utilisation of standard catchment vessels can lead to erroneous results under certain circumstances. There are also problems associated with tilling when utilising a rigid catchment vessel. It has also been found that the permanent wiring that is required to be installed underground is disadvantageous with regards to ongoing maintenance and corrosion. 
         [0004]    The present invention attempts to overcome at least in part the aforementioned disadvantages of previous soil moisture sampling devices. 
       SUMMARY OF THE PRESENT INVENTION 
       [0005]    In accordance with one aspect of the present invention there is provided a soil moisture sampling device, the soil moisture sampling device comprising a moisture collector and a measuring instrument, wherein the moisture collector is arranged to receive moisture through an opening and the measuring instrument comprises a tipping bucket and a measuring device, the tipping bucket comprising at least one magnetic device arranged to generate a changing magnetic field as measured by the measuring device. 
         [0006]    Preferably the tipping bucket comprises a first and a second magnetic device wherein the magnetic poles of the first magnetic device are aligned to be opposite relative to those of the second magnetic device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0007]    The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0008]      FIG. 1  is a schematic view of a soil moisture sampling device in accordance with the present invention; and 
           [0009]      FIG. 2  is a front isometric view of a tipping bucket of the soil moisture sampling device of  FIG. 1  in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0010]    Referring to  FIG. 1 , there is shown a soil moisture sampling device  10 . The soil moisture sampling device  10  comprises a flexible catchment vessel  12  and an instrument enclosure  14 . The flexible catchment vessel  12  acts as a moisture collector. 
         [0011]    The flexible catchment vessel  12  comprises an upper end  16  which is open and a lower end  18 . 
         [0012]    The instrument enclosure  14  comprises an upper end  20  and a lower end  22 . A first end of an overflow tube  25  is inserted into an aperture  23  located in the lower end  22  of the instrument enclosure  14  such that a second end of the overflow tube  25  is located internally of the instrument enclosure  14  above the lower end  22 . A first end of a sampling tube  27  is inserted into an aperture  29  located on a side wall adjacent the lower end  22  of the instrument enclosure  14 . A pump (not shown) is connected to a second end of the sampling tube  27  above ground to facilitate pumping of water from the instrument enclosure  14  to the surface for chemical analysis. 
         [0013]    The flexible catchment vessel  12  is arranged such that its lower end  18  is engaged with the upper end  20  of the instrument enclosure  14 . 
         [0014]    The soil moisture sampling device  10  further comprises a tube  24 . The tube  24  extends from a first end  26  located, in use, above the upper end  16  of the flexible catchment vessel  12  to a second end  28  located within the instrument enclosure  14 . The tube  24  thus passes through the lower end  18  of the flexible catchment vessel  12  and the upper end  20  of the instrument enclosure  14 . An upper portion  21  of the tube  24  is removable from the tube  24 . The upper portion  21  is the section of the tube  24  that would be located, in use, in a tillage zone  54 . Alternatively, the tube  24  may be made of a reinforced flexible material and arranged to pass through a side wall of the flexible catchment vessel  12  at a point below the tillage zone  54 . In this case, the tube  24  then rises to the surface in a region outside the tillage zone  54 . 
         [0015]    The tube  24  comprises a moisture inlet  30  and a moisture outlet  32 . The moisture inlet  30  comprises at least one aperture in the tube  24  and is located, in use, in a region internal of the flexible catchment vessel  12 . The moisture outlet  32  comprises at least one aperture in the tube  24  and is located, in use, in a region internal of the instrument enclosure  14 . 
         [0016]    The tube  24  is selectively open at the first end  26 . The tube  24  is closed at the second end  28 . 
         [0017]    A measuring means or device  34  is arranged to be inserted into the tube  24  at the first end  26  and lowered to the second end  28 . A data transfer cable  36  extends from the measuring means  34  to a data collection device (not shown). The measuring means  34  may be arranged to measure temperature, conductivity, pH level, the concentration of specific ions (for example NO 3   −, K   +  and Na + ) and magnetic fields. A tipping bucket  38  is arranged below the lower end  28  of the tube  24 . The measuring device  34  and tipping bucket  38  together comprise a measuring instrument that is useful in measuring soil moisture quantities, as will be discussed further below. 
         [0018]    As shown in  FIG. 2 , the tipping bucket  38  comprises a member  42  and a plurality of magnetic means or devices  40 . The member  42  comprises a first portion  44  and a second portion  46  separated by a non-apertured partition. The member  42  is arranged to rotate around a pivot (not shown) located between a support member  48  and the member  42 . The first portion  44  comprises an aperture  41  located at a distal end  43 . The second portion  46  comprises an aperture  45  located at a distal end  47 . A respective magnetic means  40  is arranged on each of the first portion  44  and the second portion  46  of the tipping bucket  38 . The magnetic means  40  may each be arranged such that their magnetic poles are substantially perpendicularly aligned relative to a lower surface  50  of the member  42 . The magnetic means  40  located on the first portion  44  may be arranged such that its magnetic poles are oppositely aligned relative to the magnetic poles of the magnetic means  40  located on the second portion  46 . 
         [0019]    In use, a hole is dug in soil  52  that is to be tested (see  FIG. 1 ). The soil moisture sampling device  10  is arranged in the hole. When in place the upper end  16  of the flexible catchment vessel  12  is located in a tillage zone  54 . The flexible catchment vessel  12  may be arranged in a variety of shapes depending upon the size and shape of the hole it has been arranged in. 
         [0020]    The flexible catchment vessel  12  can be used for a number of successive crops without having to be removed. When the soil  52  needs to be tilled, a narrow trench can be dug around the perimeter of the upper end  16  of the flexible catchment vessel  12 . An upper portion  56  of the flexible catchment vessel  12  can now be arranged such that the upper portion  56  is below the tillage zone  54 . The upper portion  21  of the tube  24  can also be removed from the tillage zone  54 . The section of the tube  24  that remains in the soil  52  is then capped (not shown) to prevent soil and other undesirable objects and particles entering the tube  24  during tillage. After tillage the cap can be removed and the upper portion  21  reattached to the tube  24 . Additionally, the narrow trench can be dug again and the upper portion  56  folded back to its original position. 
         [0021]    The soil moisture sampling device  10  is arranged such that the tube  24  is substantially vertical with the first end  26  thereof being above an upper surface  58  of the soil  52  in which the soil moisture sampling device  10  is arranged. 
         [0022]    The instrument enclosure  14  is arranged to be substantially empty. The tipping bucket  38  is arranged within the instrument enclosure  14  such that the tipping bucket  38  is located beneath the moisture outlet  32 . Water may collect temporarily at the bottom of the instrument enclosure  14 . This water may rise up to the level of the second end of the overflow tube  25  and then flow through the overflow tube  25  and out of the aperture  23 . A layer of gravel or sand may be arranged below the instrument enclosure  14  to assist in dispersing the water as it flows out of the aperture  23 . 
         [0023]    The water in the instrument enclosure  14  may be pumped to the surface through the sampling tube  27  by action of the pump (not shown) so that the water may be chemically analysed, for example for concentrations of fertilisers and pesticides. In addition, if the water is pumped to the surface through the sampling tube  27  prior to water flowing out of the instrument enclosure  14  through the overflow tube  25 , the amount of water can be measured to confirm the amount of water flowing through the tipping bucket  38  or to allow calibration of the tipping bucket  38 . To assist in achieving full drainage of the water through the aperture  29 , the lower end  22  of the instrument enclosure  14  may be angled down towards the location of the aperture  29 . 
         [0024]    When water moves downwards through the soil  52  it first passes through fine sand  60  and then through a filtering means  62  such as a water permeable sponge in the flexible catchment vessel  12 . The water then enters the moisture inlet  30 . The fine sand  60  and the filtering means  62  remove solid particles before the water enters the moisture inlet  30 . 
         [0025]    The water will now fill a lower region of the tube  24  where the measuring means  34  is located. The measuring means  34  measures properties of the water, for example, electrical conductivity and temperature. Water will fill the lower region of the tube  24  until the water overflows through the moisture outlet  32 . 
         [0026]    The tipping bucket  38  will receive water as it flows out of the moisture outlet  32 . 
         [0027]    Either the first portion  44  or the second portion  46  will receive water from the moisture outlet  32 . The portion that receives the water is determined by which is arranged uppermost at the time. For example, if the first portion  44  is arranged uppermost as depicted in  FIG. 2  then the first portion  44  will receive the water. When the first portion has received a predefined amount of water the weight force due to this water will cause the member  42  to tilt. The member  42  will tilt such that the second portion  46  is now arranged uppermost. The water that was collected in the first portion  44  will now flow out through the aperture  41  towards the lower end  22  of the instrument enclosure  14 . Now that the second portion  46  is arranged uppermost, the second portion  46  will receive water from the moisture outlet  32 . Once the second portion  46  has received a predefined amount of water the member  42  will tilt such that the first portion  44  is now arranged uppermost and the water collected in the second portion  46  will flow out through the aperture  45  towards the lower end  22  of the instrument enclosure  14 . This process will repeat such that each time the member  42  tilts a predefined amount of water flows out of the tipping bucket  38 . 
         [0028]    The magnetic means  40  located on each of the first portion  44  and second portion  46  will create a change in the magnetic field which is detected by the measuring means  34 . The measuring means  34  may comprise a device capable of measuring changes in magnetic fields, for example, a hall effect sensor. The measuring means  34  will therefore detect the change in the magnetic field from the magnetic means  40  each time the tipping bucket  38  tilts. Each time the tipping bucket  38  tilts a predefined amount of water has passed through the soil moisture sampling device  10 . The total amount of water passing through the soil moisture sampling device can therefore be calculated over a period of time by multiplying the number of times the measuring means  34  detects a change in the magnetic field due to the member  42  tilting by the amount of water that flows out of either the first portion  44  or the second portion  46  each time the member  42  tilts. Data collected by the measuring means  34  is transferred to a data collection device (not shown) through the data transfer cable  36 . 
         [0029]    Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.