Field of the Invention

The invention relates to a lysimeter and to an installation method for a lysimeter. The lysimeter is adapted to sample water that has drained freely, or drained under applied suction, through the soil. The invention also relates to a method of using such a lysimeter.

Background of the Invention

There are two pressing needs for a larger and more cost efficient lysimeter:

1. To provide an on-farm tool for farmers to monitor drainage and nutrient losses on-farm;

2. To statistically capture the nitrate leaching from urine patches under

grazing management.

Reliable measurement of soil drainage is critical to assist famers to achieve efficient irrigation and best-practice nutrient management. Farmers need to be able to conduct audited self-management, whereby they can directly observe drainage together with nitrate and other nutrient leaching losses, and then test how changes in management practice can lead to improved efficiency. Current methods such as suction cups and monolith lysimeters are not suited to be widely used as on-farm measurement tools. This is largely because a very large number of sample sites are required to capture spatial and temporal variability, and therefore the capital and operating costs are prohibitive.

Under dairy farming, it is particularly important to reliably intercept drainage from the late autumn and winter urine patches, which are recognised as the major source of nitrogen-leaching from dairy grazed pasture. Recent modelling work by Landcare Research has shown that even with 500 suction cups or > 100 barrel lysimeters per hectare, the autumn / winter urine patches will be under sampled and therefore leaching of nutrients will be under estimated. Modelling indicates that considerably fewer channel lysimeters are needed to achieve interception of the autumn / winter urine patches to within ± 20% of the true proportion, at a much lower cost than current methods. The large area of the new channel lysimeter means it needs to be installed in only a few locations, greatly reducing the operating cost.

Object of the Invention

It is an object of the invention to provide a lysimeter which is able to sample water passing through a substantially undisturbed soil. It is a further object of the invention to provide a method so that such a lysimeter can be inserted into the soil to collect water passing through a substantially undisturbed soil or to at least provide the public with a useful choice.

Summary of the Invention

The invention provides a new shape lysimeter and installation method for a lysimeter which is adapted to collect a drainage water sample from underneath a substantially undisturbed sample of soil.

In particular the invention provides an apparatus and a method of installing such an apparatus for collecting a drainage water sample from underneath a substantially undisturbed soil using an adequate representative sampling method, wherein the soil through which sampled drainage water passes through has not been removed or substantially disturbed from its original position prior to or during insertion of the lysimeter into the sampling site.

In particular the invention provides a lysimeter capable of collecting drainage water from a substantially undisturbed area of soil located above the installed lysimeter, the lysimeter comprising:

A collection chamber for collecting the drainage water running through the soil located above the lysimeter; and Side plates located on each longitudinal side of the collection chamber to prevent lateral displacement of water.

The chamber may be in the form of a channel.

The lysimeter is preferably substantially in the form of an H shape. This shape provides strength when the lysimeter is inserted into the ground.

However other shapes of lysimeter are conceivable and within the

embodiments described by this invention as long as the shape is able to collect the drainage water which flows through the ground above the lysimeter once the lysimeter is inserted into the ground. The shape may for example, be more of an I shape, or even substantially rounded in shape. The shape should be able to collect the water which drains trough the substantially undisturbed soil above the lysimeter and channel it to a collection means for further analysis.

The lysimeter is preferably made from metal.

It may be made of stainless steel . The lysimeter may be protectively coated to prevent corrosion.

The sides of the lysimeter should be of a suitable height, according to the type of soil into which the lysimeter is to be placed. A height of about 40cm has been found useful when no perforation is used.

The lysimeter may also include a collection means. The collection means is preferably located at one end of the lysimeter. The collection means is preferably a collection tube which collects a water sample for analysis after it has passed through the chamber or channel.The presence of water in the collection means may be relayed to a user through a communication network, most preferably a wireless cellular network. In a further embodiment of the lysimeter, a cavity may be located as part of collection chamber. The cavity preferably comprises a thin drainage means mounted on top of the base plate of the lysimeter.

In this embodiment, a perforated surface on the top of the collection chamber may be included to allow collected water to run through the perforations and into the cavity. When a perforated collection surface is used, the side walls of the lysimeter may be reduced in height.

The perforated collection surface maybe constructed of a porous material with sufficent air-entry potential that a suction may be applied by means of a suction pump or a porous wick to the cavity of the collection chamber.

The suction may aid drainage and prevent ponding on the base of the lysimeter.

One end of the H channel preferably comprises an end pate in which is located a slot or the like located level with the base plate, to allow drainage water to pass through the slot and into a collection means.

The invention also provides a method of inserting a lysimeter into the ground comprising inserting a suitably shaped collection chamber into the vertical soil face, giving access to adjacent substantially undisturbed soil, and using a double acting telescopic hydraulic ram or similar device to apply and release pressure to an end of the channel.

Preferably vibration is applied to the collection chamber with sufficient frequency and amplitude to drive the channel through the soil.

Insertion of the lysimeter may employ a system of vibration followed by a release of the ram, followed by further vibration and further release. The collection chamber is preferably in the form of a substantial H shape. However other shapes and designs are envisaged and included within the scope of this application.

The lysimeter according to the invention is in the form of a channel. There are four main advantages of a channel lysimeter;

1. It greatly increases the measurement area, and therefore improves the representation of spatial and temporal variability of drainage and nutrient losses.

2. It is more cost effective per unit area than other lysimeters. 3. It has minimal disturbance to overlying soil profiles.

4. The design is simple and robust, with few working parts, and therefore should reliably operate over a number of years with little maintenance cost.

Within this description, the meaning of "undisturbed" that the active root zone of the plants in the ground above which the lysimeter is inserted into, is not substantially moved when the lysimeter is inserted.

The invention provides a lysimeter which when inserted into soil, is able to collect drainage water over a good representative land area without having to substantially disturb the soil when the lysimeter is inserted. The lysimeter described in this specification has been designed to penetrate the soil to be analysed for water drainage with minimal soil disturbance.

For the purpose of this specification, and unless otherwise noted, the term "comprises" shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components which it directly references, but also to other non-specified components or elements. This rationale will also be used when the term "comprised" or "comprising" is used in relation to one or more steps in a method or process.

Brief Description of the Drawings

The invention will now be described with reference to the accompanying drawings in which:

Figure 1 shows a lysimeter collection chamber in the form of an H shape;

Figure 2 shows a lysimeter according to a second embodiment of the invention in which a cavity is formed beneath the collection chamber;

Figure 3 shows a lysimeter resting on the ground surface; Figure 4 shows a further embodiment of a lysimeter with a cavity beneath the collection chamber. The lysimeter is resting within an insertion means for insertion into the soil;

Figure 5 shows a collection chamber sitting within the "H" section, on top of the base plate, with a hanging wick embedded in the cavity of the collection chamber exerting a suction on the porous top of the chamber, with the suction equal to the depth the wick hangs out the end of the "H" channel;

Figures 6-9 show the method of insertion of the H channel into the soil;

Figure 10 shows the lysimeter inserted into the soil, and connected to a drainage collection chamber, with the rate and quantity monitored by a wireless sensor.

Figure 11 shows an insertion frame holding the lysimeter;

Figure 12 shows the lysimeter being inserted into the soil with a linking piece attached to enable it to be pushed further into the soil than the furthest extension of the hydraulic ram allows; Figures 13, 14 and 15 show the lysimeter within the soil;

Figure 16 shows the stress and strain method of insertion;

Figure 17 illustrates the stress and strain principle;

Figure 18 shows the lysimeter inserted in the ground with a box shape extension fitted to allow driange water to pass from the lysimeter to a the draiange collection chamber.

Figure 19 shows the lysimeter immediately prior to insertion into the ground.

The invention will now be described with reference to the accompanying drawings. It will be appreciated that the description that follows shows only certain embodiments of the invention and that variations and modifications may be made without departing from the scope of the invention as described.

Detailed Description of the Invention

The major requirement of a spatially representative lysimeter is its ability to collect draining water from a sufficiently large area of the land incorporating a mosaic of water based input sources such as distributed urine patches in dairy farms.

The present invention describes a lysimeter and a method of using the lysimeter which enables a user to sample soil drainage water to improve the efficiency of fertiliser and water application. The invention can be deployed with minimal cost and the installation procedure can be carried out with minimal training and skill. Analyses of the collected water provides reliable information to manage fertiliser application, animal management, increased productivity, and a reduction of chemical or microbial leaching to ground water. The present invention describes the method of lysimeter installation, whereby the "H" channel is inserted into the vertical face of the undisturbed soil using double acting hydraulic ram, as well as the placement of a collecting chamber;.

Example 1. Inserting an "H" channel into the soil.

A metal or stainless steel substantially H shaped collection chamber or channel is shown in Figure 1. The collection chamber includes a base plate (1) and side walls (2). An end plate is shown at (3).

The base plate (1) acts to collect drainage water, and the side walls (2) are of sufficient height to prevent lateral displacement of water.

One end of the H channel has an end plate (3) with a slot (not shown) located level with the base plate, to allow drainage water to pass through and into a collection means (not shown).. The H channel is made from metal. It may be coated in a protective coating to prevent corrosion (e.g. galvanised, plastic or paint coat), or be constructed from stainless steel.

Figure 2 shows a further embodiment of the invention. The lysimeter includes a thin drainage cavity (4) in the base plate (1).

The drainage cavity (4) is sealed on all sides, except for the point where water passes out and into a collection means (not shown). The cavity has a porous upper surface (5) which when suction is exerted into the underlying cavity (4) would act to allow drainage of water from the soil above. The suction in the cavity may be exerted by a vacuum pump, or by a porous wick (or similar material) which is embedded in the cavity (4). When saturated, the porous wick acts to exert a suction based on the depth the end of the wick is below the upper surface of the drainage chamber (6). This is most clearly shown in Figure 5. The upper surface of the drainage chamber has sufficiently pore size distribution to be able to maintain a known suction, whilst allowing a sufficient flow rate of water to pass through. It may be constructed of porous plastic, stainless steel or like material. A further drawing of the embodiment shown diagrammatically in Figure 1 is shown in Figure 4. The lysimeter is shown with side walls (2) and a base plate (1), lying in an insertion box (7) prior to insertion into the soil. In a further embodiment of the lysimeter a cavity is shown (4) through which suction may be applied. A porous wick (6) may be inserted into the cavity (4) to provide the suction.

The width, length, and side wall height of the "H" channel is determined according to the soil type. For soil with lower friction between the soil and the H channel a larger width and length can be selected. For soil with larger friction a channel with smaller width and length is more desirable. The wall height is a critical design parameter, with higher walls in soils with greater near saturated hydraulic conductivity. The lysimeter shown in Figure 3 is 2.8 m long, 0.425 m wide, and 0.4 m high side walls above the base plate (total height 0.5 m).

Central to the invention is the inserting machine (7), constructed of a solid steel frame with a sufficient capacity (example. 50,000 kg) double acting hydraulic rams (8) fixed at one end to push the "H" channel into the soil as shown conceptually in Figures 7-9 and in Figure 4. The prototype insertion machine is also shown in figures 11, 12, and 19. The guide members of the machine are constructed in such a way that the "H" channel cannot buckle under the maximum applied force. The H channel moves within the guide frame along low friction runners.

A trench or pit is dug, adjacent to the target soil, using a digger or similar machine to the width and length of the inserting machine, and of a sufficient working depth to allow the H channel lysimeter to be inserted at the soil depth of interest. This is shown in Figure 6 and 7. The insertion pit is on a sufficient slope to allow installation of the lysimeter with sufficient slope to enable drainage water to move under gravity down the lysimeter length to the drainage collection chamber. An example of the complete installation is shown in Figure 19.

If required the insertion machine can be held against the bottom surface of the pit by the digger bucket to make it more stable during the insertion of the "H" channel into the soil. Alternatively, the machine is held in place by bracing against concrete blocks (Figure 19), or bracing to a frame which may be used to support the walls of the insertion trench and prevent trench collapse.

Once the machine is well placed and stabilised and the "H" channel is in correct position the hydraulic rams (8) are activated to push the "H" section into the soil as shown in Figures 7-9. The hydraulic rams (8) can be driven by a commonly available farm tractor with a hydraulic motor.

The entire "H" channel is pushed into the soil in segments of lengths equal to the maximum travel of the hydraulic cylinder(s) or ram(s) as shown in Figures 7- 9. After inserting one segment length of the H channel a spacer block (9) with sufficient strength is placed in between the bearing plate and the "H" channel as shown in Figures 8 and 9 and the procedure is repeated. This is shown in Figure 12.

Alternatively, the hydraulic rams may be telescopic rather than single flight rams, and the channel can be inserted without the spacer blocks. Alternatively, a sufficient number of short lengths of "H" channels can be driven as segments using a short trench rather than digging a long trench, and joined (welded, bolted) in situ. Figures 3, 11 and 19 show photographs of an "H" section channel sitting in the installation guide frame.

Improvements to method of driving channel into porous media.

Driving the "H" channel collection means into gravelly or stony soils can be improved by applying vibration to the channel with sufficient frequency and amplitude to the driven "H" channel using a pneumatic vibrator driven by a tractor or air compressor.

After many test installations of the channel lysimeter, a naval driving method which is called in this specification "stress & strain relaxation" has been invented. This is quite different to the current sheet pile driving method used in civil engineering construction work which is based on directional vibration only. The new method is shown most clearly in Figure 16 (and in Figure 19 of the prototype). In this Figure, the lysimeter is shown at (10) and the insertion machine at (11). A linker (12) is used between the lysimeter (10) and the ramming means (13). The linker is also shown in Figure 3. The method involves uni-directional vibration (14) under static stress exerted by the telescopic ram and cyclic relaxation of both stress and strain (15). .

The principle is shown in Figure 17. This allows large grains (gravels) to resettle around the channel lysimeter wall preventing ground heave on the ground surface. This drives the channel lysimeter in gravelly soil without creating massive disturbance to the subsoil.

Once the "H" section is inserted to one side of the pit, the inserting machine can be lifted from the pit, turned 180° and then returned to an identical depth in the pit with a new "H" channel in its chamber. The same procedure is followed to insert another "H" section into this other vertical face of the pit. Therefore, two lysimeters are installed using a single pit. Multiple lysimeter channels may be installed in "STAR" configuration, using two trench's that cross in the centre.

Another alternative installation configuration is where one or more lysimeter channels can be installed out of one side of a pit (for example a fan type configuration). In all instances the inserted channels may connect back to their own drainage collector (16), as shown in Figure 10, or multiple channels may drain to a single shared collector. The drainage collector may contain instruments to allow drainage rate and volume to be measured by sensors connected to a communications medium which may engender remote data access.

Other sensors may also be installed, including an automatic sample collector to enable known aliquot samples to be collected at regular time periods, or an automatic drain valve which may allow emptying of the drainage collector when required.

Figures 13, 14 and 15 show the installed lysimeter and indicate the degree of disturbance to the gravels around the lysimeter after installation. Figure 14 shows the front end of the lysimeter, and Figures 13 and 15 the solid rear end,, with drainage slot to allow the drainage water to move to the collection chamber. It can be seen that the soil above the inserted lysimeter is

substantially undisturbed.

Table A shows a comparison of analysis methods used to sample water as it drains through soil. The table compares known suction cap methods with known barrel lysimeter methods with the presently described invention, termed in Table A "channel lysimeter". It will be appreciated from Table A that the channel lysimeter method provides numerous advantages over known methods in terms of cost of installation, coverage and operating costs. A key advantage of the present invention is that the soil through which water drains prior to entering the lysimeter for sampling has not been disturbed or removed and re-introduced from its original position prior to or during the insertion and positioning of the lysimeter into its sampling position. Table A

Industrial Applicability

The invention relates to a lysimeter which is adapted to be inserted into soils to collect drainage water for future analysis. The lysimeter is of such a design that it can be inserted into soil without substantially disturbing the soil through which the water which is to be analysed flows prior to being collected in the lysimeter. The lysimeter hence provides a good spatial soil representation to allow analysis of water which drains through a certain area of soil. This is useful to farmers to monitor drainage both in turns of water levels in the soil and in terms of analysing chemical content of water drainage through soils. The invention also provides a method of inserting the lysimeter without

substantially disturbing the soil through which water to be monitored drains.