Trickle irrigation system

[57] ABSTRACT

A system for irrigating a crop by a method commonly known as the trickle irrigation method or “drip” irrigation. The device has a primary duct to which irrigating water is supplied and at least one secondary duct either extending alongside in parallel relationship with the primary duct, or extending away from the primary duct. When the secondary ducts are situated to extend alongside the primary duct they are internally partitioned into a number of chambers. Each chamber is in fluid communication with the primary duct via at least one flow restricting transfer passage and is also provided with a plurality of flow restricting outlet passages. The number of outlet passages exceeds the number of transfer passages for a particular chamber. When the secondary ducts extend away from the primary duct the flow restricting transfer passage is provided in its connection to the primary duct and the secondary duct has a plurality of outlet passages. With the above systems the pressure of the irrigating water supplied is reduced by both the transfer and outlet passages and by being progressively sub-divided into a plurality of streams and thus the irrigating water issues from the system in the form of a plurality of low pressure trickles or drips. Lengths of small bore tubing may be placed in the outlet passages to allow further pressure reduction while the heights of the outlets of the small bore tubes may be adjustable above the secondary duct to enable more precise adjustment of the output from the system.

Claims, 18 Drawing Figures

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PATENTED JOH 2 7 is??

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PATENTED JUN 2 7 1972

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PATENTED JUN 2 7 1972

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TRICKLE IRRIGATION SYSTEM

This invention relates to a system for irrigating crops by a method commonly known as the trickle irrigation method or “drip” irrigation.

It has been recognized for many years that spray or flood irrigating is not suitable for many crops particularly in areas where efficient utilization of available water resources is required.

In order to achieve efficient irrigation the trickle method of irrigation has been developed. This form of irrigation involves controlled application of water to the root zone of individual plants in a crop.

Trickle irrigation may be defined as the daily maintenance of an adequate section of the root zone of a plant at, or close to, field capacity for the duration of the growing season. Evidence shows that crops give better yields with the more even water regime afforded by this system of irrigation.

There are two basic methods presently being utilized for applying water by the trickle method.

One method uses very narrow bore micro tubing (sometimes called “plastic string,” “spaghetti” or “capillary” tubing). These tubes are inserted into polythene lateral pipes and the high friction losses in them are used to control pressure and hence flow.

While the micro tube itself is cheap the problem of inserting it into the laterals quickly is still to be overcome.

The second method commonly known as the Blass method differs from the pipe and micro tube method mainly in the equipment used. The device essentially allows small quantities of water to be released from a pressurized line through relative large outlets.

The Blass system consists of three main components which may be varied to meet specific requirements. The first of the components is a control head consisting basically of a riser from a supply source, a valve, pressure gauge, water meter and filter. To this may be added a fertilizer dispenser which bypasses a certain percentage of the following water through a fertilizer tank on a differential pressure basis. The control head may be further refined for automatic or semi-automatic control.

The second component is a reticulation system to which water is passed from the control head, and comprises a system of lateral pipes to the crop area.

The third component is a multiplicity of dripper hoses made from a special grade of polythene. The drippers are in practice at 18 inch or 3 foot centers while the pipes are spaced between rows ranging, for example, from 4 to 6 feet apart.

Attempts have been made to bury the system to take full advantage of the controlled evaporation from the soil surface where moisture performs no useful purpose. However, it was found that blockages of the drippers occurred and that such a dripper failure was difficult to detect.

Trickle irrigation has many advantages including increased yields, and with young trees accelerated growth. The root zones remain moist at all times especially at critical growth stages. The plant is not subject to continuous cycles of soil saturation to wilting point and the consequent set-backs to its growth.

The ability to water and fertilize concurrently by virtue of the addition of nutrients dissolved in the irrigation water is also advantageous.

Significant water savings are obtained and the spaces between rows remain firm and dry so assisting spraying and harvesting operations. The method has also been found to be particularly useful on undulating ground and hillsides.

However, present systems have some disadvantages including the need for very efficient and consisting filtration due to the very small bore outlet, a problem which is further increased when solid nutrients are added.

Also some known systems involve great expense due to the requirements for elaborate nozzles, and further difficulties have been encountered in obtaining accurate and controlled pressure drops through the systems.

It is an object of the present invention to overcome the above mentioned disadvantages in known systems.

The basis of the system according to the present invention resides in a system in which a single high pressure stream of irrigating water is progressively sub-divided into a plurality of smaller streams at a lower pressure or pressures.

According to one preferred form of the invention water at a relatively high pressure is passed into a primary duct which extends from one end of the crop area to the other alongside the rows of plants constituting the crop. The water is tapped through a few relatively large fluid restricting transfer passages provided in a wall dividing the primary duct from a secondary duct placed alongside to extend with the primary duct. These transfer passages from one duct to the other are widely spaced along the length of the dividing wall. The secondary duct contains a larger number of fluid restricting outlet passages through which water trickles to the root zone of adjacent plants.

Over relatively short distances no significant pressure drop will occur over the length of the primary duct, however, once larger distances are traversed significant pressure drop occurs.

Preferably this is overcome with the present invention by increasing the diameter of the transfer passages proportionally to the pressure drop experienced.

The secondary duct is internally partitioned into separate chambers into each of which water is supplied by one of the passages provided in the dividing wall. This construction enables interference of the pressure head caused by undulating ground to be substantially obviated.

Each separate chamber in the secondary duct is provided with a plurality of outlet passages and the spacings between these outlet passages is determined by the particular spacings of the plants in the crop to be irrigated. The outlet passages are once again larger relative to those used in known systems.

The water at high pressure in the primary duct will be reduced to a lower pressure upon transfer into the secondary duct from which by virtue of the fluid restricting transfer passages and the further division among a plurality of outlet passages, and issues from the secondary duct in a plurality of low pressure trickles.

More than two ducts may be provided with each duct supplying water to the next duct with the plurality of holes increasing in number from duct to duct. With a plurality of ducts the number of streams progressively increases as the water transfers from duct to duct thus causing a progressive reduction in pressure throughout the system.

The system may preferably be further refined when circumstances require extra accuracy, or slower application of water, by inserting lengths of small bore tubing into the outlet passage. The small bore tubing is not meant to embrace tubing with bore sizes as small as that of micro tubing. The further friction losses encountered in the small bore tubing causes a further pressure drop thus resulting in drips rather than a continuous issuance of water.

But even more importantly where small bore tubes are used they may be supported at any required height to balance precisely the output of each outlet. This adjustment is only small and is quite practical due to the low pressure head in the secondary duct, and in fact the actual size of the small bore tubing is of least importance, in that the major factor influencing adjustment of the output is the positioning of the height of the outlet from the small bore tubing.

According to another preferred form of the invention, the same sub-division to produce a low pressure trickle may be accomplished by a modified system wherein instead of a single secondary duct partitioned into a plurality of chambers and extending alongside the primary duct with each chamber being in fluid communication with the primary duct, a plurality of secondary ducts are used, each duct constituting a single chamber. Each duct is in fluid communication with the primary duct through a fluid restricting transfer passage. These secondary ducts do not necessarily extend alongside the primary duct, but may in fact diverge from the primary duct.

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4

With this modified system the primary duct may extend alongside the field of the crop being irrigated, while each secondary duct extends along the rows of the crop and delivers trickles of water to the root zone of each individual plant.

This modified system still performs the basic method of the 5 invention in that the single high pressure stream of irrigating water is progressively sub-divided into a plurality of smaller streams at lower pressure or pressures.

This modified system may be extended to the three or more duct system contemplated above, but instead of the ducts ex- 10 tending alongside each other in parallel relationship, each extra duct diverges from its associated supply duct. For example, with the three duct system a plurality of third ducts are provided, one for each outlet from the secondary duct. With such a system the secondary ducts may be spaced at a distance 15 embracing a number of rows of the crop with the third duct extending adjacent each plant in the crop to supply irrigating water.

With the above systems a filter if desired would only need to be a simple coarse filter in order to prevent any unduly large solids entering the ducts and small bore tubing.

The invention therefore envisages a system for irrigating a crop by the trickle or drip method, including a primary duct into which irrigating water from a supply is passed, one or more secondary ducts attached to, or formed integrally with, the primary duct, at least one flow restricting transfer passage between said ducts allowing transfer of water from said primary duct to a secondary duct with an accompanying drop in pressure, said secondary duct, or ducts, including a plurality of flow restricting outlet passages allowing transfer of water from the secondary duct, or ducts, to the crop with an accompanying further drop in pressure, with the number of said outlet passages exceeding the number of said transfer passages for each Secondary duct, whereby the irrigating water will issue from said secondary duct, or ducts, onto the crop in a plurality of low pressure trickles or drips.

Various forms of systems, and modifications thereof, incorporating the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a plan view of part of an irrigating system according to one preferred form of the invention;

FIG. 2 is a more detailed view of part of the system of FIG. 1 showing the duct construction in greater detail;

FIG. 3 is a section view taken along line 3—3 of FIG. 1;

FIG. 4 is a plan view of part of an irrigating system according to a second preferred form of the invention;

FIG. S is a section view taken along line 5—5 of FIG. 4;

FIG. 6 is a cross-section of a duct construction according to a third preferred form of the invention;

FIG. 7 is a cross-section of a duct construction according to a fourth preferred form of the invention;

FIG. 8 is a general view of a duct construction according to a fifth preferred form of the invention;

FIG. 9 is a general view of one of a pair of forming rollers for producing ducting of the construction shown in FIG. 8;

FIG. 10 is a plan view of part of an irrigating system layout according to a sixth form of the invention;

FIG. 11 is a plan view of part of an irrigating system layout according to a seventh form of the invention;

FIG. 12 is a more detailed view of the duct interconnections of FIG. 11;

FIG. 13 is a diagrammatic view of a preferred way of achieving adjustment of flow through the transfer passage interconnecting the primary high pressure and secondary low pressure 65 ducts in a twin parallel duct system;

FIG. 14 is an illustration of the utilization of an irrigating system according to the invention as particularly adapted to the irrigation of potted plants in hot houses;

FIG. 15 is an illustration of an irrigating system according to 70 the invention adapted for use in irrigating crops on undulating or sloping land;

FIG. 16 is a section taken along line 15—15 of FIG. 15;

FIG. 17 is an illustration of an irrigating system according to the invention adapted for the irrigation of young trees; 75

FIG. 18 is an illustration of an irrigation system according to the invention adapted for the irrigation of mature trees.

Referring particularly to FIGS. 1, 2 and 3, the irrigating system, generally indicated as 1, comprises a main supply duct 2, which supplies irrigating water to a distribution duct system 3 (only one of which is shown), via a connecting passage 4, and a flanged connector 5.

The duct system 3, comprises a primary duct 6 of approximately three-fourths inch in diameter made from polythene piping to which irrigating water at a relatively high pressure is supplied from the supply duct 2. Integral with or attached such as to form a water-tight connection with the primary duct 6, is a secondary duct 7 of approximately one-half inch in diameter, with the adjacent walls of the two ducts containing a number of flow restricting transfer passages 8, (only one of which is shown in FIG. 2), enabling transfer of water from the primary duct 6 to the secondary duct 7. The transfer of water to the secondary duct will be accomplished by a drop in pressure. The transfer passages 8 by way of example, are about one-sixteenth inch in diameter, although as previously mentioned where large distances are to be traversed the diameter of the passages are progressively increased to compensate for the pressure drop.

The secondary duct 7 is partitioned, by means of seals 9, into a plurality of chambers 10, with a transfer passage 8 supplying each chamber. The wall of the secondary duct is provided with a plurality of flow restricting outlet passages 11. Preferably each chamber of the secondary duct contains ten outlet passages 11. Preferably the outlet passages 11 are also one-sixteenth inch in diameter.

In order to obtain a drip supply lengths of small bore tubing 12 are inserted into each outlet passage 11. The bore of the small bore tubing is preferably in the range of one-sixteenth to one-eighth inch.

For a particular application the transfer passages are provided at 10 foot spacings for 100 feet. The secondary duct is the same length as the primary duct and the outlet passages are provided at 1 foot intervals for. 100 feet. This gives a preferred transfer passage to outlet passage ratio of 1 to 10.

FIGS. 4 and 5, show a modification of the embodiment shown in FIGS. 1 to 3, wherein the distributing duct system 13 includes a further secondary duct 7α, also integral with or attached to the primary duct 6, and supplied through transfer passage 8α. Irrigation water is supplied to the crop through outlet passages Ila and lengths of small bore tubing 12α. This allows distribution to rows of the crop extending adjacent each side of the distributing duct system.

Although the above described preferred embodiment utilizes a one stage pressure reduction between the ducts, the inventive principle may be extended to use with any number of ducts, for example, by providing a third duct 14, see FIG. 7, with the outlet passages 11 from the secondary duct 7 forming part of a transfer passage to the third duct 14, thus providing further pressure reduction stage. In this case the water eventually issues from outlet passages 15 and small bore tubes 16 in the third duct 14. The third duct would be partitioned similarly to the secondary duct with the ratio between the number of transfer passages to the third duct and the number of outlet passages from the third duct being once again preferably 1 to 10.

Although the above described embodiment utilizes the aforementioned ratios between the number of transfer passages and outlet passages these are merely only preferred values and alternative ratios may be selected dependent upon the particular pressure reduction desired and/or the length of the rows and the spacings between individual plants. Also the size of the various components are preferments only and other suitable sized components may be employed.

In a further modification of the above distribution duct system construction the secondary duct 17, see FIG. 6, is formed or fixed inside the primary duct 18. This twin duct version may comprise a ½ inch pipe inside a % inch pipe, with a part of the outside wall of the inner pipe being jointed to a part of the inside wall of the outside pipe. The transfer passages 19

3,672,571 are provided in the wall of the inner duct whilst the outlet passages 20 are provided through the jointed wall portions of inner and outer ducts 17 and 18. Lengths of small bore 21 may be inserted into the outlet passages 20.

As a further alternative to joining the primary and secondary ducts, or integrally forming or extruding them, the twin duct construction may be produced by taking a relatively large tubular pipe placing it between a pair of suitable shaped forming rollers to produce a duct as shown in FIG. 8.

The rollers are so shaped as to press and seal, by heat or a strong adhesive applied to the interior of the pipe, two opposed portions of the interior surface of the pipe together, to form a primary duct 22 separated from a secondary duct 23 by a web 24. At spaced intervals along the interconnecting web 24 pressure is relieved such as not to allow the inner portions of the pipe to be united. The relieved areas 25 produce the transfer passages 26 between the primary duct 22 and the secondary duct 23. Outlet passages 27 are also provided in the secondary duct. These outlet passages may be produced in the pipe before formation or may be produced after formation of the secondary duct. FIG. 9 shows one of a pair of rollers suitable for producing the ducting of FIG. 8. The roller, generally indicated as 33, is supported for rotation on a support shaft 28, and has formed into its surface a circumferentially extending groove 29 of substantially semi-circular cross-section for shaping the primary duct 22, and a smaller circumferentially extending groove 30 also of semi-circular cross-section for shaping the secondary duct 23. Between the two grooves a substantially flat surface 31 is provided which together with the corresponding surface on the other of the pair of forming rollers presses certain portions of the piping supplied to the rollers together and unites them to form the web 24. At least one notch 32, extending parallel to the axis of rotation of the roller 33, is provided, which will allow relief or pressure at certain portions along the web to prevent the pipe being united at these portions and to allow the production of transfer passages 26. If it is desired to produce transfer passages at more frequent intervals in the web, two or more notches may be provided around the circumference of the surface 31.

FIG. 10 shows a departure from the parallel distributing duct system of FIGS. 1 to 9, wherein the secondary duct 34 instead of extending alongside the primary duct 35 and attached thereto in fluid communication with the primary duct, diverges away therefrom, and in fact in FIG. 10 it extends away at right angles to the primary duct. The primary duct 35 is connected to the main supply duct 36 by a connecting passage 37 and flanged connections 38, in a similar manner to that shown in FIGS. 1 and 4.

With the embodiment of FIG. 10, the primary ducts 35 extend along the ends of a number of rows of plants making up the crop to be irrigated, whilst the secondary ducts connected to the primary duct, extend along between the rows. Irrigating water issues from the secondary duct to each individual plant through small bore tubes 39.

FIG. 11 shows a modification of the embodiment of FIG. 10, wherein the distributing duct system comprises a three duct construction, providing a further pressure reduction stage. In this modified form a plurality of third ducts 40 are provided, attached to, and in fluid communication with, the outlets from the secondary ducts, and diverge away from the secondary ducts. In particular as shown in FIG. 11 the third ducts 40 extend away at right angles to the secondary ducts. The third ducts 40 are provided with outlet passages into which small bore tubes 41 are inserted to allow distribution of irrigating water to the root zones of the plants of the crop.

FIG. 12, shows a portion of the system of FIG. 11 in more detail, and particularly shows the connection between the three ducts 35, 34 and 40 making up the distribution duct system. The construction includes a flow restricting passage 42 between the first and second ducts 35 and 34, and a further flow restricting passage 43 between the second and third ducts 34 and 41.

FIG. 13 shows a simple regulating device which may be used in a parallel duct system similar to that shown in FIGS. 1 to 5, wherein a tapered screw 47 is screwed into the ducting transversely through a secondary low pressure duct 43, such that its end lies within and axially aligned with the transfer passage 45 from a primary high pressure duct 44. By screwing the tapered screw 47 inwardly or outwardly the cross-sectional area of the transfer passage 45 is reduced or increased.

With all the embodiments so far described with reference to FIGS. 1 to 13 a trickle of irrigating water is produced merely by progressive division of flow as per the parallel duct system or the diverging duct system wherein the irrigating water by virtue of progressive sub-division and reduction in pressure trickles directly from the secondary duct or ducts through small bore tubes, or if further stages are used, directly from the last lowest pressure duct through small bore tubes and onto the root zone of the plants in the crop.

This production of trickle purely by division is particularly applicable where a relatively high rate of discharge is acceptable.

As previously mentioned the trickle may be further controlled more accurately and at a low discharge rate by using an overflow principle through the small bore outlet tubes. By supporting the outlet from the small bore tubes above the low pressure duct to which they are communicated, low discharge rate can be achieved to such an extent that the discharge is in the form of drips.

This application uses reduction in pressure by division of flow, followed by further reduction in pressure by using small bore tubes the outlets of which are raised above the level of the duct to which they are attached. This system has particular use in greenhouses or outdoors on level or near level ground and is ideally suited for container grown crops.

FIG. 14, shows application of the invention where the crop consists of plants grown in containers such as pots. A wire crotch 48 may be inserted into the earth in a pot 49 to support the outlet end 50 of the small bore outlet tube 51 above the secondary low pressure duct 52 from which it is being supplied.

FIG. 14, shows a parallel duct situation where secondary duct 52 is supplied by primary high pressure duct 53.

Where outlet tubes are used to produce minimal pressures the highest point of rise of the tube should be adjacent the outlet of the tube or excess pressure will be required at the beginning of each irrigation in order to initiate flow.

The outlets of the tubes are preferably shaped to prevent water from running back down the outside of the tube.

One further particular form of the invention which has been found to be particularly applicable to sloping or undulating crop areas and market gardens, is the “quick more rigid” system as shown in FIGS. 15 and 16, wherein sections 54 of the ducting system are rigidly supported at a set level. The sections for example, may be 10 or 20 feet long. All outlets 55 for a particular rigid section will therefore be at the same level and supply from these outlets will be approximately at the same rate.

The duct sections 54 may be made from rigid materials with spikes 56 attached to rigid support channels 57 to be driven into the ground to a chosen distance to hold the duct substantially horizontal. One rigid section may be connected to another at a lower level by a fluid conducting communicating duct 58.

The rigid sections may be used singly, in parallel and/or series, with or without small bore tubes to give drips or trickles.

To facilitate setting the height of the outlet points in all small bore outlet tube applications (except in the “quick more rigid” system) it is preferable to temporarily connect a float valve tank to provide a fixed head of supply. Using a screw down valve the adjustment of one outlet affects flow rate from the others.

Although it is considered a disadvantage to locate the outlets above ground level, on the credit side it will be recognized that the virtue of an instant visual check is of marked im3,672,571 portance. Although the possibility of blockage is unlikely with this system, a ruptured pipe or other interference even though remote is an ever present danger. With the system mounted above ground level, failure of supply at any point will be detected before death of the plant occurs. Also any system that delivers water at or below ground level is susceptible to invasion of its outlet orifice by thirsty roots.

Where the crop consists of young trees the small bore outlet tubes may be supported by stakes driven into the ground adjacent the base of the tree. In a particular application, as shown in FIG. 17, the stake 59 is made from hollow pipe with the pipe being in fluid communication with the low pressure duct 60, and an outlet 61 from the pipe provided further up the pipe into which an outlet tube 62 is inserted. The stake 59 may be attached to the trunk of the tree 63 by a loosely fitting noose 64 such as to slide relative to the tree during growth. When a hollow pipe is used as a stake, outlets may be provided at several levels so as to enable adjustment of the rate of flow from the pipe by selecting a particular outlet, and inserting a small bore tube into that outlet whilst the remaining outlets are plugged.

For more mature trees, where the root zone is more widely spread, a number of arms 65 may be provided on the hollow stake 67, as shown in FIG. 18, which stake is in fluid communication with a secondary duct 68. The arms have outlets 66 disposed away from the trunk of the tree thus delivering irrigating water to the areas to which the roots of the tree extend. In such an application the arms 65 may be of various lengths to facilitate irrigation at various distances away from the base of the tree.

With both the embodiments of FIGS. 17 and 18, the ducts 60 and 68 may be primary high pressure ducts while the stakes themselves form the secondary low pressure ducts.

The above described embodiments utilize ducting systems provided by polythene piping but pipes made from other types of materials may be utilized.