This invention relates to a system for irrigating and draining the soil in which plants are to be grown.

According to the invention, there is provided a soil irrigation and drainage system which comprises, below the soil, a solid layer of a highly absorbent material possessing capillary action and which the roots of plants growing in the soil above said layer cannot penetrate, means for supplying water to the absorbent layer, and means for controlling said supply of water so that the level of saturation of said layer is maintained below the upper surface of said layer supporting the soil.

As will be clear from the later description, the invention is applicable both to open or enclosed areas of ground such as football pitches, golfing greens, grass tennis courts, ground within greenhouses, and the like, as well as to plant container systems whether in the open or in greenhouses.

The system operates to maintain an adequate supply of water to the plants growing in the soil, by upward capillary action through the layer from the saturation level, whilst preventing waterlogging of the soil which is damaging to the plant roots. The more water is drawn by the plants, the greater the upward movement of water by capillary action, and the greater the amount of water drawn by the absorbent layer from the water supply means in order to maintain the saturation level within the layer. Generally, this saturation level may be set higher, but always below the top surface of the absorbent layer, for plants using a larger amount of water, and lower

for plants which require less water. The saturation level may also be adjusted to suit weather conditions when the system is employed in open ground, being set higher in drier and/or hotter conditions.

When the system is used in the open, then under conditions of heavy rainfall drainage of water may be backwards through the water supply means either to an overflow or to storage for later use. Alternatively, surplus water may be taken from the absorbent layer by a drainage means separate from the water supply means.

A preferred material for the absorbent layer is cement containing a blend of moisture absorbent fillers. Most desirably the absorbent cement layer is rigid at all times after initial setting, whether wet or dry, and, in, addition to possessing a strong capillary action, is capable of absorbing water to at least 65 percent of its dry weight.

The absorbent layer may be either pre-cast in blocks to be laid on site, or cast _ n situ, as will be clear from later ^" description.

The irrigation and drainage system in accordance with the invention is exemplified in the following description, making reference to the accompanying drawings, in which:-

Figure 1 shows an absorbent block of cementitious material;

Figure 2 shows a plant container incorporating the block of Figure 1;

Figure 3 again shows a single plant container;

Figure 4 shows the manner in which plant containers can be coupled together;

Figure 5 shows a miniature garden made up of containers in accordance with the invention;

Figure 6 shows a modified plant container system;

Figure 7 is a composite figure illustrating four possible applications of the invention;

Figure 8 is a cross-section through an area of ground irrigated and drained in accordance with the invention;

Figure 9 shows a football pitch irrigated and drained in accordance with the invention;

Figure 10 shows details of the arrangement of Figure 9; and

Figure 11 shows a golfing green irrigated and drained in accordance with the invention.

Referring to Figure 1, there is shown a preformed rigid block 10 cast in a mould from a cementitious material containing a blend of moisture absorbent fillers, whereby the block has a strong capillary action in addition to an ability to absorb water up to at least 65 percent of its dry weight. Perlite may be used as the filler for the cement, but a blend of cellulose fibres may alternatively be employed, amongst other possibilities. The block 10 is cast on the underside with a channel 12 extending from one side of the block to the other. Typically, the block may be about 10 cm deep.

Figure 2 shows a plant container 14 having a bottom part 16 of reduced cross-section in which is received the absorbent

block 10 of Figure 1. A water supply pipe 18 releaεably connects to a pipe stub 20 which extends in substantially sealed manner through the side wall of the container 14 to communicate with the channel 12 in the block 10.

The supply of water through the pipe 18 is controlled to maintain saturation of the block 10 up to the level 22.

Above the block 10, the container 14 is filled with soil 24 which, in general, will be constituted by a growing medium suited to the plant or plants to be grown in the container.

In use, the roots 26 of a plant 28 in the container 14 draw water from the soil 24, the moisture content of which is maintained as the soil in turn draws water from the block 10 by upward capillary movement of water from the saturation level 22. The block 10, in its turn, draws water from the water inlet pipe 18 to maintain the saturation level 22.

Although as the plant grows the roots 26 may reach down to the top of the block 10, they are unable to penetrate into it, and therefore cannot grow downwards into water-saturated ^' conditions devoid of oxygen and which are liable to cause root rotting. Moreover, although as it grows the plant 28 may use an increasing amount of water, the saturation level 22 is always maintained. Furthermore, if the container 14 is full of plants of a kind using large amounts of water, then if desired the water supply controller can be adjusted to raise the saturation level 22. However, this level 22 is always kept below the level of the top of the block 10.

If in use the container is stood in the open, so as to receive rainfall, the system also acts to drain away surplus water which would otherwise saturate the block 10 above the

saturation level 22. In this case, water flows backwards through the inlet pipe 18, either to an overflow or into storage ready for later use.

In the simple form of planter shown in Figure 3, a single container 14 is equipped with an upright water inlet pipe 30 for manual watering and incorporating a float level indicator 32. Regular watering through the inlet pipe 30 is carried out to maintain the float within minimum and maximum levels. Although in this simple case some variation in the saturation level within the absorbent block 10 in the container 14 takes place, this is not of major significance provided that the maximum float level is not exceeded.

More usually, two or more containers 14 will be coupled together, as indicated in Figure 4 by coupling pipe 34, so that water can flow from the channel in one block into the channel in the next block, whereby all the blocks become saturated to the same controlled level. This saturation level may be controlled by a valve, such as a float valve, operative in the water supply means.

Figure 5 shows a series of containers 14A, 14B.... 14H abutted to one another in front of a wall 36 and inter- connected by coupling pipes 34A. The water supply means, connected to one container of the series, say the end container 14A, is not shown. The drawing also shows that the exposed side faces of the containers may be decoratively covered, as indicated at 38. Plants grown in the containers may include plants 40 trained to grow up the wall.

An alternative arrangement of container system in accordance with the invention is shown in Figure 6, wherein the absorbent blocks 42 at the bottom of the containers 44 are

moulded with through-holes instead of open channels. Pipes 46 containing apertures 48 pass through the through- holes, and coupling pipes 50 interconnect the containers, which in this instance are spaced apart instead of being abutted against one another. A water supply means connects to one end of the system and water is supplied to the absorbent blocks 42, to maintain a required saturation level therein, through the apertures 48 in the pipes extending through the blocks 42.

Systems such as those shown in Figures 5 and 6 may in practice be embodied as a miniature garden, in which a large decorative outer container or frame carries a plurality of interconnected plant containers as hitherto described, together with a reservoir tank from which the plant containers are supplied with water via a chamber containing a float valve for controlling the saturation level in the absorbent blocks. The plant containers need not be connected in a straight line; it is only necessary that all the containers be interconnected to receive water from the water supply means. Moreover, the frame may have more than one tier, with plant containers on more -'than one level, the reservoir being provided at the highest level and each level having a water supply controller in the form of a float valve.

For convenience, four possible systems in accordance with the invention are all illustrated in Figure 7, although no relationship between the systems is intended to be implied by this composite figure.

Figure 7(a) shows a system comprising five plant containers 52 individually fed with water from a feed pipe 54. The feed pipe 54 itself receives water from a reservoir 58 via

a float valve 58 in a chamber 60, thereby to control the saturation level in the absorbent blocks provided, as hitherto described, in the containers 52. An overflow 62 is provided in the form of an upwardly open elbow piece at the end of the feed pipe 54.

Figure 7(b) shows a larger system in the form of a matrix of containers 64 containing absorbent blocks and inter¬ connected with one another, as by channels moulded into said absorbent blocks, so that all the containers receive water from a feed pipe 66 under the control of a float valve 68 in chamber 70. An overflow 72 from the system is provided adjacent the chamber 70.

The aforesaid overlows 62 or 72 will become operative if there is a failure of the valve control in the water supply means or, more usually, if the containers are situated on an open site receiving rainfall, the containers receive excess water which would cause the absorbent blocks to become saturated above a chosen level below the top surfaces of the blocks. This chosen level for saturation is variable by means of an adjustment facility provided at the float valves 60 or 68.

Typically, the saturation level will be set between 2.5 and 7.5 cm below the top surfaces of the absorbent blocks. The higher the permitted saturation level, the faster is the capillary action to the top of the blocks and thus into the growing medium.

In the afore-described applications of the invention, the absorbent blocks are pre-cast and of appropriate size and shape and laid within respective plant containers. However, the blocks could less desirably be cast in situ within the

containers under some circumstances, for example if the internal apertured pipes 46 of the system of Figure 6 are fitted within the containers first, prior to pouring in the appropriate amount of absorbent cementitious material and allowing it to set to form a rigid block around the pipe in each container.

This possibility conveniently leads to a further aspect of the invention, for irrigating and draining substantial areas of ground such as lawns, golfing greens, grass tennis courts, and even football pitches or the like.

Thus, referring to Figure 7(c) there is diagrammatically shown an area of ground 74 which has been excavated to a depth of about 25 cm, a polythene layer laid in the bottom and up over shuttering all round the perimeter of the area, apertured pipes 76 fed from a feed pipe 78 laid on or just above the polythene layer, a layer of absorbent cement having capillary action cast over the entire area between and around the apertured pipes 76 to a depth of about 10 cm, and, after the cementitious material has set, the soil replaced to a depth of about 15 cm above the absorbent layer. The feed pipe 78 is fed from a reservoir via a float valve 80 in a chamber 82 outside the area of ground being treated. An overflow pipe 84 is also provided.

The system of Figure 7(c) is later described in more detail, although a simple cross-section is shown in Figure 8, wherein the polythene layer is referenced 86, the shuttering 88, the absorbent cement layer 90 and the overlying soil 92. The cross-section also shows one of the apertured pipes 76 passing through the absorbent layer 90.

Referring to Figure 7(d), this figure shows that an area of

ground 74A to be treated may alternatively be irrigated and drained by laying a matrix of abutting pre-cast absorbent blocks 94 over the polythene layer, the blocks having channels or apertured pipes, as previously described, which interconnect so that all the blocks receive water from a feed pipe 96 itself fed from a reservoir via a float valve 98 in a chamber 100. An overflow is indicated at 102.

Figure 9 shows in more detail the manner in which a football pitch may be irrigated and drained. Figure 9(a) shows the treated football pitch diagrammatically, the turf layer being referenced 104, the absorbent cement layer 106, and the series of apertured pipes passing through the absorbent layer being referenced 108.

First, as indicated in Figure 9(b), the area of the pitch is excavated to a depth of about 30 cm. The excavated area is then levelled and covered with a 5 cm layer of sand which is rolled and levelled. A polythene membrane is then laid over the sand, and the apertured pipes 108 are laid in position over the polythene membrane, transversely across the pitch, between three main feed and drainage pipes 110 of larger diameter which extend longitudinally of the pitch. Subsequently, the absorbent cement layer is cast n situ over the entire area, to a depth of about 10 cm, thus completely covering the apertured pipes, although the tops of the main feed and drainage pipes may be exposed. Soil and turf to a depth of 15 cm is then replaced over the absorbent cement layer, after said cement layer has set.

Figure 9(c) shows an edge detail of the system in somewhat diagrammatic manner. It can be seen that the main pipes 110 serve for the dual purpose of water supply and water drainage. Thus, the apertured pipes 108 connect to the

lower part of a main pipe 110, this lower part being fed from a water supply pipe 112. The upper part of the main pipe 110 connects to a drainage pipe 114. The saturation level 115 for the absorbent cement layer 106 is set below the level of the top of this absorbent layer, which generally corresponds to the level of the bottom of the drainage pipe 114, so that water is only drained when, due to rainfall, saturation would tend to occur above the preset level for saturation. The saturation level is set by a controller, such as a float valve, in the water supply to the pipe 112. Water is fed to the supply pipe 112, via the saturation level controller, from a reservoir or sump which is connected to the mains water supply, but which also serves as a reservoir for water drained from the pitch through the drainage pipe 114. For completeness, in Figure 9(c), reference 116 denotes the sand layer, reference 118 the polythene membrane, and reference 120 the shuttering which is installed around the edge of the pitch and over which the polythene membrane is extended.

Figure 10 shows in cross-section certain relevant details of the arrangement of Figure 9, and employs the same reference numerals as Figure 9. Thus, Figure 10(a) shows a detail of the installation of the main water feed and drainage pipe 110 at the perimeter of the football pitch, whilst Figure

10(b) shows a corresponding detail at the centre of the pitch. Figure 10(c) shows a waterproofing flange employed at the water supply inlet and drainage outlet, whilst Figure 10(d) shows a detail of the shuttering 120.

Figure 11 shows, in analogous manner to Figure 9, the manner in which a golfing green, which has a non-level contour, may be treated. In Figures 11(a) and 11(b), the following reference numerals are used to denote the various parts of

•li¬

the system.

Reference 122 denotes the sand layer, reference 124 the polythene membrane and reference 126 the perimeter shuttering. A main water feed and drainage pipe is referenced 128, dividing outside the perimeter into a water supply pipe 130 and a water drainage pipe 132. Reference 134 denotes the apertured pipes within the cast cementitious absorbent layer 136, and reference 138 the turf and soil layer on top of the absorbent layer. Reference 139 denotes the water saturation level, which is below the top surface of the absorbent layer 136.

The system of Figure 11 will be generally clear by analogy with the description of Figure 9, but attention is drawn to the manner in which the changing levels of the golfing green are dealt with. Thus, in Figure 11(a), five distinct sections 140, 142, 144, 146 and 148 of the irrigation and drainage system can be seen. Section 148 is located beneath a hummock, which as viewed is further distant than the flatter part of the green in front of it, where section 146 is provided. Each section of the system which is on a different level has its own main water feed and drainage pipe supplied with water through a water level controller, in order to impart the correct saturation level in the absorbent cement layer in that section. Additionally, however, within individual sections, as for example indicated in sections 142 and 144, the thickness of the absorbent cement layer may be graded to match the slope of the golfing green. Figure 11(b) also shows how the changing levels of the golfing green are dealt with, including the shuttering 150, 152 provided between the different sections of the system.

In the foregoing description, frequent reference is made to

the soil layer above the absorbent cement layer. Especially in the case of a plant container system, the soil may be constituted by any growing medium appropriate to the plants to be grown and the term "soil" is to be interpreted accordingly.

Again, while reference is made to supplying water, it is also to be appreciated, again especially in the case of a plant container system, that soluble nutrients for assisting plant growth may be added to the water in the reservoir.

The water level controller may be constituted by any one of a variety of devices instead of a float valve. For example, when the system is used to irrigate and drain substantial areas of ground, a moisture sensor may be located in the treated ground,to feed back a signal to an electronic water supply controller which controls the saturation level. In this way the saturation level can be automatically adjusted to suit the prevailing moisture content of the ground.

Again, especially when the system is used in dry and hot climates, the plants grown in the containers or in the ^~ treated ground may be planted through a polythene film covering the soil, thereby to conserve water by reducing evaporation. Also in connection with possible use in hot and dry climates, it should be mentioned that preliminary experiments have shown that the system may, at least to a limited extent, be fed with salt water.

More particularly in the case where substantial areas of ground are being treated, the supply and drainage of water may be effected by means of pumps (using a vacuum pump for drainage), which transfer water between the irrigation and drainage system and an adjacent sump or reservoir, which may

then be located underground. The pumps can be automatically controlled to maintain a desired saturation level of the absorbent cement layer, for example under the supervision of one or more moisture sensors which detect the moisture content of the treated area of ground.

Various other modifications of the above-described and illustrated arrangement are possible within the scope of the invention defined in the appended claims.