FIELD OF THE INVENTION

This invention relates to drainage and/or irrigation.

BACKGROUND TO THE INVENTION

It is well known that maximum plant growth will occur when conditions of water supply, air supply, nutrient supply and temperature are ideal for a particular plant but in practice it is very difficult to achieve those ideal conditions.

Where plants are grown in the open air, as distinct from in hot houses or in other protected environments, very little

can be done about temperature control but it is still possible to have an effect upon water supply, air supply and nutrient supply.

Factors affecting nutrient supply include the amount of nutrient supplied and the manner of nutrient supplied.

Factors including air supply, particularly to the roots of a plant, involve that the water supply to the plant should neither be excessive or insufficient and that air is able to penetrate the soil.

It is often the case that where there has been excessive watering, either by rain fall or by irrigation, air access to the plant is reduced and as a consequence, plant growth is severely reduced or even stopped and in an extreme condition of water logging occurring and continuing over a substantial period, decomposition by anaerobic action can result in plant death.

One of the problems with irrigation is that it has a tendency to be applied excessively and this is not considered to be desirable although it is very difficult to control.

Indeed, the applicant has noted that in a region in Northern Victoria, crop production in a year in which total rainfall was only 3.5 megalitres per hectare was superior to other areas in which growers relying on irrigation applied 12 megalitres of water per hectare.

Applicant has observed that most irrigation systems, particularly flooded irrigation, saturate the soil initially and result in a period of slow growth but as the water penetrates the ground and moves downwards, the plant will pass into a period where the water content of the ground becomes ideal or close to ideal while at the same

time air can sufficiently penetrate and good growth will result. As the water is used up and/or penetrates deeper into the ground, the water content of the ground will become insufficient and growth will slow again.

With excessive water use in flood irrigation, most of the applied water passes below the plant root zone and can cause a rise in the natural water table. A rising water table has a subsequent increase in salinity and causes degradation of the land.

Thus, irrigation, while widely used, does have some severe problems associated with it in that it tends to produce a situation of feast or famine.

It is further to be noted that most irrigation is applied from above, either by sprinklers or by flood irrigation, and this tends to encourage surface rooting of plants rather than deep roots and this is not considered to be desirable.

The use of drip irrigation or micro sprinklers in which irrigation water is applied at more regular intervals than is usually done with flood irrigation has caused many improvements but is still highly localised and usually is at substantial cost.

Attempts have been made to irrigate below the surface of the ground. Among the advantages of such practices are the application of water and nutrients in a region where it will be better appreciated by the plants and at the same time keeping the top surface of the ground relatively dry which will reduce problems of weed germination and diseases such as fungi attack and various forms of collar rot.

Subsurface irrigation is an established practice which typically uses tape designed for above ground irrigation

use but buried underground. Such tapes have emitters which are designed to give low flow rates eg between 0.5 to 2 litres per hour. These low flow rates are required so that the water has time to soak into the ground without running off the surface.

One method of subsurface irrigation uses an expensive dripper system but problems can occur in that plant roots may enter into the dripper system and there is a need for an expensive filtration system to avoid clogging of small drippers.

Further, servicing of such subsurface drippers is difficult and expensive.

Applicant has also experimented with the use of agricultural drain pipe as an irrigation system which has larger holes than most drippers but has had difficulty in controlling the flow.

Subsurface irrigation according to the prior art has a number of disadvantages in addition to those discussed above.

Such disadvantages include the following:

1) At the low flow rates the water soaks vertically down into the ground with very little sideways or upwards movements, other than as may be achieved through capillary action, giving a very small irrigated area per dripper. This requires close spacing of the dripper lines and subsequent expense.

2) The soil around the dripper is totally saturated, while away from the emitter the soil is still dry.

3) There is no sign above the ground of the extent of the

irrigation eg whether the soil is wet underneath or not, so in practise excess water tends to be applied with significant loss of water.

The current invention seeks to improve the effectiveness of subsurface irrigation by providing a more effective water distribution, with good water spread and avoiding saturation.

SUMMARY OF THE INVENTION

The present invention provides:-

a method of drainage and/or irrigation comprising

inflating a flexible pipe located beneath the surface of soil to so disturb the soil as to cause a channel or tubular cavity to form in the soil and thus facilitate water passage in the soil in the region of the pipe.

The present invention also provides a method of preparing soil for drainage and/or irrigation which comprises laying a flexible pipe capable of being inflated in the soil.

PREFERRED ASPECTS OF THE INVENTION

The pipe may be inflated with air or water or a combination of the two.

In some circumstances the pipe may be inflated by air on some instances and with water in other instances.

Due to the relative incompressibility of water as compared to air, water will generally be the preferred inflating medium.

It is preferred that the flow rate of water from the pipe

is chosen to be substantially higher than the natural infiltration rate of the surrounding soil so that the water is forced upwards and outwards under pressure, as well as downwards.

It is also preferred that the inflation of the pipe by water is carried out in a series of pulses of predetermined duration.

The channel or tubular cavity can be used to receive a flow of water, possibly with nutrients, for the purpose of watering plants.

The channel or tubular cavity can also be used for drainage.

The channel or tubular cavity can also be used to allow air to gain access to plant roots. Further, the flexible pipe can be used to introduce air in repeated expansion and collapsing.

Total collapsibility of the flexible pipe is not essential.

In general it is thought that the collapsibility of the flexible pipe will be sufficient if the cross-sectional area of the flexible pipe in the inflated and deflated condition is in a ratio of 2:1 or, more preferably, 9:1.

To obtain adequate drainage, it may be necessary to inflate the flexible pipe a number of times to achieve the desired channel or tubular cavity.

In one particular mode of operation in irrigation, the flexible pipe is laid on a slope or is otherwise provided with a means for providing water under pressure which may be a header tank or a pump.

It is preferred to supply water to the upper end of the flexible pipe so that water flow receives the assistance of gravity.

It is also possible to supply water to the lower end of the flexible pipe by pumping and to take water from the upper end of the pipe to a header tank or other water reservoir.

The header tank reservoir or pump can be used to ensure that there is a head of water, which in its own right, will assist in pressurising the flexible pipe.

After the pipe has been inflated by water it will be usual to release water pressure from within the flexible pipe and this may be done by simply turning off a pump or by disconnecting so as to allow water to flow back out of the pipe and, as this occurs or if the water is actually pumped out of the interior of the flexible pipe, the flexible pipe will tend to collapse.

Water from the upper header tank reservoir or pump as the case may be can then be caused to flow into the channel or tubular cavity so formed and in one instance, where a particularly flexible pipe is used, the pipe will lay flat at the bottom of the channel or tubular cavity and thereby reduce water loss through the bottom of the channel or tubular cavity when water is flowed into the channel or tubular cavity from the upper header tank or reservoir.

In use, of the method of this invention on flat ground, it may be necessary to provide positive pumping or a sufficiently and appropriately catered reservoir or header tank to generate the pressure required.

A preferred method of irrigation comprises a periodic cycle of a phase of pulse injection of water followed by a relaxation phase in which drainage can take place.

Several of the flexible pipes might be used and it may be convenient that they could be joined together at ends which are adjacent one another so that a single pump or header tank or reservoir might be used.

Further, when two pipes are used, they might be sequentially inflated so that water coming from a free end of one of the pipes could enter into the channel or tubular cavity formed by the other one of the pipes when it is in deflated condition.

The pipes will probably be laid parallel to one another but are not necessarily laid side by side and may be separated from one another by distance which will generally have regard to the plants that are to be grown.

The flexible pipe may have holes, which are preferably triangular and not more than 7mm, or emitters to allow water to flow to soil. The pipe has holes or emitters in the pipe spaced at regular intervals (preferably 650mm).

The preferred emitter comprises three slits emanating from a single point in a tri-star configuration in a size range of 2.4 - 5.5mm and is referred to as a flapper valve. In addition a multi-slitted flapper valve comprising more than three slits may also be used. The flapper valve has the characteristics that the valve is normally closed, however under pressure the valve will open giving a high flow rate.

An additional advantage of the flapper valve is that in its open state, it has an orifice which is large enough to allow particular matter of small to moderate size to pass therethrough. Thus, it is suitable for the passage of animal wastes into the soil.

The cyclic expansion and contraction of the pipe and the use of flapper valves which remain closed ensure that roots

do not penetrate the emitter of the pipe system.

Controller means which might include a moisture sensing device and level switches or timers might be provided to make operation at least substantially automatic.

It is not desirable that the channel or tubular cavity should collapse and thus in initial installation of the flexible pipe, the inflation should desirably be applied for a sufficient period of time or sufficiently often to compact the soil to firm up the channel or tubular cavity. It is also to be noted that plant roots will also give stability to the channel or tubular cavity and to the soil thereabouts.

In this last respect, some plants will have root systems more suitable for the above purpose than others and thus companion planting should be considered.

For instance, a vineyard might comprise a number of rows of vines which are spaced apart and a crop such as grass, oats, alfalfa, peas or beans or other legumaceous plants might be grown in between the rows of vines and should stabilise the soil and in the case of legumaceous plants, provide nitrogen.

The top layer of the soil is naturally more porous partly because it is dry and partly because of natural organic material in the soil. Part of the process may include one or more steps to modify the natural permeability of the soil by a combination of cross working the soil eg scarifying or harrowing perpendicular to the pipe line and the addition of organic material such as the use of green manure and the use of additives such as fish oil, animal wastes, clay breakers, nutrients or other conventional soil conditioners directly to the water.

During the relaxation or drainage cycle the water will experience difficulty in permeating downwards due to the compacted wet soil below the pipe but find it easy to move in a horizontal manner.

Reservoirs or header tanks may contain nutrients as desired or may have vegetable matter included therein which will mulch down and rot and form a natural form of fertiliser.

Animal manures may be similarly used in the header tanks or reservoirs.

The diameter of the flexible pipe is not critical, applicant prefers that the pipe has a diameter, when inflated, which falls substantially within the range of 20 - 35mm. For particular circumstances, however, smaller or larger pipes may be used. For example, when a long flow run is required, a larger diameter pipe is used. Applicant has used pipes of 65mm diameter and 200mm diameter.

Several lengths of the flexible pipe may be joined end to end in any convenient manner.

One convenient manner is to use a rigid joiner piece. However, under some circumstances, internal pressure may provide a sufficiency of the seal between two pipes.

A seal may be provided at one end of the flexible pipe and such a seal is preferably openable when desired although in certain circumstances it may not be desirable to open the seal.

The flexible pipe may be laid in the ground by forming a trench and feeding the pipe through a tube having a end located in the trench.

The present invention will be further illustrated with the

aid of the accompanying drawings which relate to non- limiting examples.

BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWINGS

Figure 1 shows a schematic arrangement for irrigation.

Figure 2 is a detail of part of the arrangement shown in Figure 1,

Figure 3 shows a cross-section of a collapsed flexible pipe during a relaxation cycle of an irrigation process.

Figure 4 shows a cross-section of a flexible pipe during pulse injection of water.

Figure 5A shows a perspective view of an emitter in the form of a flapper valve in its closed position,

Figure 5B shows a perspective view of the flapper valve of Figure 5A in its open position, and

Figure 6 shows a schematic arrangement as an alternative to the arrangement shown in Figure 1 involving a series of irrigation pipes leading from a manifold pipe line.

In the figures, the solid arrows show the direction of water flow along the pipe.

INTEGER LIST

1. Sloping ground

2. Top reservoir

3. Bottom reservoir 4. Flexible pipe

6. Trench

7. Pump

8. Channel or tubular cavity

9. Flapper Valve

10. Manifold line

DETAILED DESCRIPTION WITH RESPECT TO THE DRAWINGS

Generally, a tractor is used to construct a trench as an initial operation and thereafter the or another tractor provided with flexible pipe laying apparatus is used to lay a flexible pipe 4.

In essence, the pipe laying apparatus comprises a tube which feeds the flexible pipe 4 to a desired distance below the ground and forms a preliminary hole in the ground to accept the flexible pipe 4.

The flexible pipe 4 comprises polyethylene thin walled tube of about 200mm in diameter when inflated.

In Figure 1 is shown sloping ground 1 at the top of which is a reservoir 2 and at the bottom of which is a reservoir 3.

A flexible polythene pipe 4 has been laid in a trench 6 and the top end of the pipe 4 empties into the top reservoir 2 and the bottom end of the flexible pipe 4 is connected via a pump 7 to the bottom reservoir 3.

The flexible polythene pipe 4 is provided with emitters in the form of flapper valves 9 (as shown in Figure 5) which are regularly spaced along the pipe 4 at intervals of approximately 650mm.

In use, water is pumped up the flexible pipe 4 from the bottom reservoir 3 and in so doing will cause the pipe 4 to expand thereby forming a channel or tubular cavity in the ground 1. In addition, the water entering the pipe 4

causes the flapper valves 9 to open and force water under pressure into the soil.

Alternatively, the water may be pumped downhill to make use of the assistance provided by gravity. In this case pumping can be by reverse cycle of the pump 7 at the foot of the slope or by another pump (not shown) at the top of the slope.

The flow rate of water from the flapper valve 9 emitters is chosen to be higher than the natural infiltration rate of the soil (eg 4 to 20 litres per hour per emitter) so that the water is forced upwards and outwards under pressure, as well as downwards. This is schematically illustrated in Figure 4 with the arrows and contours showing the direction and pattern of moisture flow.

Inflation of the flexible pipe 4 is done a number of times in the form of pulses of water flow to carefully form the channel or tubular cavity 8 and distribute water into the soil.

The time of water flow is relatively short, for example between 5 minutes to 1 hour. The timing of flow is selected so that water is not wasted by allowing it to penetrate below the plant root zone or to reach the surface of the soil.

When the pump pressure is released at the end of a pulse, the water will tend to flow down the sloping ground 1 back to the bottom reservoir 3 and in consequence the flexible pipe 4 will tend to collapse (as shown in Figure 2 and also shown in Figure 3) so that the channel or tubular cavity 8 will be available for water to be flowed within it for the purposes of irrigation and/or for drainage of excess water from the soil.

Figure 3 illustrates the relaxation phase of the process after a pulse of water and shows the direction and pattern of moisture flow.

Not shown in the Figures is one or more soil moisture sensors buried in the ground, typically midway between adjacent flexible pipes 4.

The sensors are adapted to operate the pump 7 to control the pulse cycles. The pulses occur on a regular basis according to a timer but the total number of pulses is determined by the soil moisture sensor such that when the moisture reaches a predetermined valve no more water is applied. Similarly, when the soil moisture falls to a second predetermined value, the pump 7 will be reactivated and the pulsing will begin again.

The use in this process of the lay flat flexible pipe 4 which collapses when unpressurised allows a drainage channel or tubular cavity 8 to be formed in the ground 1 for either redistributing irrigation water or to remove excess water from rainfall. This drainage tends to draw air back into the soil and hence can aid in aeration of the soil.

As an adjunct to the process, air pressure can be used to maintain the flexible pipe 4 open during periods of non- irrigation and to provide a drainage channel during wet periods such as winter.

In cases where pressure drops along the pipe cause a variation in the quantity of water exiting from each of the flapper valves, an arrangement as shown in Figure 6 can be used.

In this arrangement, a high pressure manifold line 10 is employed. A series of individual flexible pipes 4 is laid

in the ground and connected to the manifold line 10 as shown. Water is pumped into each pipe 4 at a relatively high pressure and as it passes the bottom of the U of the pipe, the pressure has dropped to a medium level and as the pipe 4 returns to near the manifold line 10, the pressure has dropped to a low level. The direction of water flow is shown by the arrows in Figure 6. With this arrangement, the average water distribution into the soil between the arms of each pipe 4 is constant because the sum of the flow rates from the adjacent arms of the U will be substantially uniform at all points along the pipe 4.

Experiments conducted by the applicant show that the flexible pipe can be expanded to create numerous small fissures or cracks in the soil and this will be effective in drainage and in irrigation and will also help in aeration of the soil.

The claims, illustrations and drawings form part of the disclosure of this specification as does the description, claims, illustrations, photographs and drawings of the associated provisional specification, all of which are imported hereinto as part of the record hereof.

Finally it is to be understood that various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements or parts without departing from the spirit and ambit of the invention.