GB2585162A - A hydroponic crop growing system - Google Patents

Abstract

A hydroponic crop growing system 1, using nutrient film technology, comprises a suspension assembly 8; a relatively rigid gutter 7 suspended by the suspension assembly; a relatively flexible gully (21, figure 3) supported by the gutter and extending in a length direction of the gutter; multiple inlets 26 at which a nutrient solution is introduced into the gully at first positions along the gutter; multiple drains 27 where nutrient is drained from the gully at second positions along the gutter, with a plurality of runs (29, figure 6) along the gutter defined between adjacent first and second positions, wherein the gradient of each run is between 1.27 and 1.35 percent, with the gutter comprising at least four runs, providing the gutter with a W-shape when viewed in side elevation. This system is particularly, but not exclusively, suitable for growing tomatoes in glass houses. Also disclosed is a method of growing tomatoes in the system as claimed and tomatoes grown by the system as claimed.

Description

A Hydroponic Crop Growing System The present invention relates to a hydroponic crop growing system that is particularly, but not exclusively, applicable to the growing of tomatoes in glasshouses.

Traditionally, tomatoes were grown in glasshouses in peat, but in the 1980s large commercial growers started to use irrigation techniques using RockwoolTM avoiding the use of peat.

Subsequently, nutrient film technology was tried, whereby a solution of nutrients would run along troughs in which the tomato plants were growing, but this did not prove particularly popular for tomato growing, partly because of the requirement for the ground to be well graded to achieve a sufficient and uniform slope, which in turn effectively restricted the potential growing area. Because of this, most growers have reverted to irrigation techniques growing commercial crops with a substrate such as RockwoolTM, Coir, etc, enabling growers to buy well tested and what are essentially off the shelf irrigation systems.

It is an object of the present invention to provide a system which employs an improved nutrient film technique, which may offer advantages over the above described irrigation type systems.

According to a first aspect of the present invention there is provided a hydroponic crop growing system using nutrient film technology for growing crops, the system comprising: a suspension assembly; a relatively rigid gutter suspended by the suspension assembly; a relatively flexible gully supported by the gutter and extending in a length direction of the gutter; multiple inlets at which a nutrient solution is introduced into the gully at a plurality of first positions along the gutter; and multiple drains where nutrient is drained from the gully at a plurality of second positions along the gutter, wherein: a plurality of runs are defined along the gutter between respective adjacent pairs of first and second positions; the gradient of each run is between 1.27 and 1.35 percent; the gutter comprises at least four runs providing the gutter with a W-shape when viewed in side elevation; and wherein the system further comprises a nutrient reservoir for receiving nutrient solution from the multiple drains and a dispensing system for dispensing nutrient solution from the reservoir to the multiple inlets.

An advantage of a hydroponic crop growing system in accordance with the present invention is that it permits a crop to be grown directly in a nutrient film without the requirement for a substrate. such as Rockwool TM. This has the advantage that, where properly regulated, each plant may be supplied with a uniform and constant level of nutrients set at levels for the optimum growth of the plant and for maximising the value of the crop.

A system in accordance with the present invention avoids the need to grade the ground within a glasshouse for the gradient of the gully may be set by controlling the gradient of the gutter on which the gully is supported, by making adjustments to the suspension assembly from which that gutter is suspended, when initially setting up the system.

A particular advantage of the present invention, in having a gutter which, when viewed in side elevation, is W-shaped is that particularly long runs of gutter may be formed such that each row, defined by a gutter, may be in excess of 100 meters. However, the W-shaped profile maintains the gutter along its length at a generally uniform height convenient for both working at and to ensure good ventilation below and around the gutter, to assist in healthy growth of plants by maintaining a uniform temperature and humidity.

A gradient for each run of between 1.27 and 1.35 percent has, by trial and error, been found to be the optimum gradient of a run, permitting sufficient nutrient flow to ensure the plants along the length of a run obtain generally uniform nutrition, with the gradient of each run preferably being uniform along the length of each run.

The W-shape gutter permits the total length of each run to be significant in terms of commercial growing, normally in excess of 130 metres. This enables large scale production techniques to be applied, for example by using rails between adjacent rows to permit equipment to easily pass along the rows to assist in planting, harvesting or subsequent clearing. However, at the same time, the W-shape limits the length of each run and ideally the length of each run is less than 32 meters. This is desirable because it has been found that with a run in excess of 32 meters there begins to be significant differences in the levels of nutrients received by the plants at respective ends of such a run. Thus the W-shape may permit a row to be, for example, 125 meters long, desirable for commercial growing in large glasshouses, but may permit the length of each run to be approximately 30 meters long, with the inlets for nutrients in the gullies positioned at each end of the gully and at a midpoint and with drains located at approximately 30 meters and 90 meters along the gully, or gutter.

The W-shape gutter can be extended to be a VW-shaped gutter or a WW-shaped gutter, or any other such multiple.

The provision of a reservoir for receiving the nutrient solution from the multiple drains permits the nutrient solution to be pumped into the inlets at a rate far greater than the rate at which the nutrient solution will be consumed by the plants in an associated run, this ensuring that the nutrient solution is evenly distributed along the run and that substantially the same quantity of nutrients are available to the plants towards the drain as they are to the plants towards the inlet.

Preferably, each gutter, in cross-section, has a substantially planar upper surface with a depression in a central region of less than 10mm deep, with the width of each gutter preferably being more than 300mm wide.

An advantage of such a system is that it permits the gutter to act merely as a support for the gully, which gully may preferably be formed from a polythene sheet or similar, with the gutter then defining a substantially flat base of the gully where the sheet forming the gully will follow the profile of the gutter. The depression in the central region of the gutter has the advantage of both providing a reinforcing spine for the gutter, reducing the number of points at which the gutter needs to be suspended and also defining a central channel to concentrate flow along the centre of the gutter, to ensure the flow along the gutter doesn't by-pass the blocks of the plants when they are initially placed in a gully and before the roots start to more fully develop.

A width in excess of 300mm enables two rows of tomato plants to be accommodated in a single gully, while providing sufficient space for the roots to spread without unduly restricting flow along the gully, although as the root mass increases the depth of the nutrient solution in the gully will tend to increase.

Each gutter may be formed from multiple lengths of metal sheet joined, or at least overlaid, end to end to provide a continuous gutter of the desired length and the joins between the lengths may be used to accommodate the W-shaped side profile of the gutter, but because the gradients are relatively slight this will normally be accommodated by distortion of the sections of the gutter. Preferably, each suspension assembly comprises two wires running parallel to the associated gutter, with the two wires supporting respective sides of respective gullies. In this way, very little additional structure or mass is required in order to form the gullies from a relatively cheap length of polythene or similar flexible material. The advantage of forming the gully of a relatively inexpensive polythene sheet means that a gutter may be formed and suspended and left in place as a permanent structure, with a gully then being laid out and formed on the gutter, which gully can then be replaced after each crop, whilst leaving the correctly inclined gutter in place for the growing of subsequent crops.

Preferably, the reservoir comprises a tank with at least one return pipe entering the tank at a tank inlet, for returning nutrient solution to the tank from one or more drains, the return pipe entering the tank at a level above the level of nutrient solution in the tank, the system comprising control means to control the level of nutrient solution in the tank, to maintain the level in the tank at a predetermined level below the tank inlet.

An advantage of the above mentioned arrangement is that a certain level of splash may be provided by the returning nutrient solution, acting to aerate the nutrient solution in the tank, for an aerated solution assists in healthy plant devopment.

Preferably, the above mentioned tank is a first tank and the reservoir comprises a second tank for receiving overflow nutrient solution from the first tank. This permits the first tank to be maintained at a constant level with surplus nutrient solution being stored in the second tank, helping to assist in maintaining a constant splash in the first tank from the returning nutrient solution. However, to help further improve aeration a mixing pump may be used to aerate the nutrient solution in the first tank.

A system in accordance with the invention may further comprise a drip pipe suspended above the length of the gully by the suspension assembly. This may permit young plants to initially be fed by a drip until the roots develop to an extent where it is preferable to pump nutrient solution along the gullies. The drip pipe may also be used at different stages through the growth cycle if this should be desired.

Preferably, the system described above comprises overhead high pressure sodium lighting with intermediate level LED lighting at a level intermediate the height of the crop, such that as the plants develop the overhead lighting may be supplemented by LED lighting at lower levels where the overhead lighting penetrates to a lesser degree. This supplemental lower level lighting has been found to enable crops to be grown in the UK all year round.

Preferably, the system further comprises means for monitoring the nutrient levels in the nutrient solution, the monitoring means monitoring the conductivity of the nutrient solution and controlling the dispensing of concentrated nutrients into the solution in dependence thereon.

According to a second aspect of the present invention there is provided a method of growing tomatoes, the method comprising assembling a system as described above and placing tomato plants in the gullies. Preferably, the method further comprises drip irrigating the tomato plants until they reach a particular stage and then commencing the dispensing of nutrient solution into the gullies at the multiple inlets and more preferably, once commenced, the nutrient solution is dispensed continuously until a crop is substantially ready to be harvested.

One embodiment of the present invention will now be described, by way of example only, with reference to the accompanying figures, of which: Figure 1 is a side elevation of a section of a hydroponic crop growing system in accordance with the present invention; Figure 2 is a section through the crop system of Figure 1 taken along the line of Figure 1; Figure 3 shows to an enlarged scale the components of a suspension assembly of the crop growing system of Figures 1 and 2; Figure 4 shows a further components of the suspension assembly of the crop growing system of Figures 1 and 2; Figure 5 is a side elevation corresponding to Figure 4; Figure 6 schematically illustrates how the gutter of a crop growing system in accordance with the present invention may have a W-shape profile, in side 25 elevation; Figure 7 shows how a gutter of a crop growing system in accordance with the present invention may have a VW-shape when viewed in side elevation; and Figure 8 illustrates the component of a reservoir for use with the crop growing system of Figures 1 and 2.

Referring now to Figure 1, this shows in side elevation a section of a hydroponic crop growing system in accordance with the present invention, indicated generally as 1, and this comprises a trellis, indicated generally as 2, comprising a plurality of uprights 3 which support an upper frame 4. The upper frame 4 can be seen more clearly in Figure 2, a section taken along the line II-II of Figure 1, shown to an enlarged scale.

Mounted to the upper frame 4 are multiple high level high pressure sodium lamps 5.

The growing system comprises a plurality of gutters 7 arranged side by side to define a plurality of rows, which rows will typically run of the length of a glasshouse in which the crop growing system will normally be housed.

Each row may comprise a single gutter 7, possibly extending the length of a glasshouse, or alternatively a row may be made up of two or more gutters 7 arranged end to end with access pathways provided between adjacent gutters 7 of a row.

Each gutter 7 is relatively rigid and may be formed from a pressed metal sheet or as an extrusion, possibly from a plastic material. A gutter 7 may be formed of multiple sections which may either be joined together or overlapped. Each gutter 7 is suspended from the upper frame 4 by a suspension assembly indicted generally as 8.

Each suspension assembly 8 comprises a plurality of primary suspension assemblies, indicated generally as 9, and a plurality of intermediate suspension assemblies, indicated generally as 10.

The primary suspension assemblies 9, can only be seen in Figure 2, for these lie in line with the uprights 3 of the trellis 2, when viewed in from side elevation of Figure 1. Each primary suspension assembly 9 is suspended from a cross member of the upper frame 4. Each primary suspension assembly, shown more clearly in Figure 3, comprises a wire 11 attached to the upper frame 4.

Attached to the lower end of the wire 4 is intermediate member 12, having a primary cradle 13 attached to a lower end. The primary cradle 13 is formed out of a piece of metel rod bent to have a substantially triangular shaped main portion 14 and an extension portion 15 for attaching to the intermediate member 12. The extension portion 15 has a support bracket 16 for supporting a grow pipe 17. The grow pipe 17 is a relatively rigid metal pipe which is supported by multiple primary suspension assemblies and runs the length of gutter 7.

The triangular shaped main portion of the cradle 13 is arranged to open at point 18, such that each cradle 13 may be clipped over a length of gutter 7 so that the gutter 7 is accommodated within the primary cradles 13.

As can be most clearly seen from Figure 3, the gutter 7 has a substantially n-shaped profile with an extensive, substantially flat upper surface having a slight depression 22 in that upper surface.

In the embodiment shown, the gutter is 350mm wide with 4.4mm deep depression extending across the central 150mm of the upper surface of the gutter 7.

Two wires 19 and 20 are also attached to the primary cradle 13 at the position shown. These are used to support respective sides of a strip of polythene sheet running the length of a gutter 7, the opposite edges of the polythene sheet being draped over respective wires 19 and 20 and clipped in place, such that the polythene sheet forms a gully 21. Because the polythene sheet is relatively flexible the gully 21 on its lower face adopts the profile of the top surface of the gutter 7.

In the embodiment depicted, the gully 21 is arranged to accommodate two rows of tomato plants and the depression 22 in the top surface of the gutter 7 ensures that nutrient solution passing along the gully does not bypass the blocks of the plants before the roots start to develop.

As described below, the hydroponic crop growing system 1 is arranged so that a thin film of nutrient solution flows along each gully 21 with, as can be seen from Figure 3, the grow pipe 17 used to distribute the nutrient fluid to various points along the gutter, where it is fed via hoses 26 into the gully 21.

As can been seen from Figure 1, each gutter 7 is also supported from the grow pipe 17 at a number of intermediary locations by the intermediate suspension assemblies 10. One of the intermediate suspension assemblies 10 is shown in front elevation in Figure 4 and in side elevation in Figure 5. From Figures 4 and 5 it can be seen that each intermediate suspension assemblies 10 is very similar to and function in a similar manner to the primary suspension assemblies 9 of Figure 3. One notable exception is that instead of having a support bracket 16 to support the grow pipe 17, as per the primary suspension assembly 9 of Figure 3, the intermediate suspension assembly of Figure 10 instead has a hook 23 for engaging over the grow pipe 17 such that the grow pipe 17 supports intermediate suspension assembly 10 and thus the gutter 7. Thus the grow pipe 9, necessary for the distribution of nutrient solution, also functions as a support for the gutter and thus considerably reduces the number of components that would otherwise be required to form the upper frame 4.

Referring now again to Figures 1 and 2, these additionally show arrays of LED lighting units 24 arranged end to end and suspended by wires 25. These provide intermediate lighting within the canopy of the fully developed plants, which supplements the lighting from the high-pressure sodium lamps 5 at lower levels within the canopy where the light from the sodium lamps 5 may not fully penetrate.

The gully 21, fabricated from the polythene sheet is not shown in Figure 1, but from a comparison with Figure 3, for example, and from the above discussion, it will be apparent that the two hoses 26 seen in Figure will convey nutrient solution from the grow pipe 17 into the gully 21.

In Figure 1, only a section of the gutter 7 is seen and this section is V shaped in the side profile shown. The gutter 7 has a low point towards the middle of the section of the gutter as shown in Figure 1 and here there is located a drain 27 for receiving nutrients from a hole in the polythene sheet forming the gully 21.

The length of each section of the gutter 7, between a hose 26 supplying nutrient solution and the drain 27, defines a run and the gutter is arranged such that each run has a slope of between 1.27 and 1.35 percent, with each run having a length of 30 meters or less. This combination of slope of the run and length of the run has been found to provide ideal conditions, providing an adequate supply of nutrients to the plant roots along the entire length of each run, while avoiding waterlogging, particularly as the root mass increases. Because nutrients are supplied relatively uniformly to plants along the length of each run, the nutrient solution received at the drain 27 is still rich in nutrients and this is returned along an underground drainage line 28 to a reservoir for replenishment and recirculation, the reservoir being described below with reference to Figure 8.

Figure 1 shows only a section of a gutter 7 and the whole gutter instead of being V-shaped, as shown in Figure 1, is instead W-shaped shaped as shown schematically in Figure 6, with the gutter 7 forming four runs 29, each with an associated nutrient solution feed in the form of a respective hose, represented by arrows 26 and with respective pairs of runs 29 sharing a common drain, represented by the arrows 27 shown. Such a gutter 7 will extend in excess of 100 meters and the advantage of making the gutter W-shaped, with the four shorter runs of less than 30 meters, as opposed to a longer run of over 100 meters or two shorter runs of over 50 meters, is that the roots are supported at a fairly uniform height above ground level in the glasshouse. This ensures that all the plants along a run are exposed to substantially identical environmental conditions, for they are substantially at the same level, noting that humidity and temperature will vary significantly at different levels within a glasshouse. Furthermore, it ensures the plants are uniformly spaced from the floor at a minimum height, which is preferably greater than 700mm and more preferably greater than a meter, which provides both a safe working height and reduces the likelihood of stagnant and damp air being present below the plant roots which may encourage disease. Depending on the length of a glasshouse and the desired length of gutter within that glasshouse, the W-shaped gutter of Figure 6 may be extended to be a VW-shaped gutter as shown in Figure 7, or may be extended further to be a WW-shaped gutter or \A/VW-shaped gutter, etc. Referring now to Figure 8, this shows a reservoir indicated generally as 29 of the system. The reservoir 29 comprises a main tank 30 and an overflow tank 31.

The main tank 30 has three inlets 32, each connected to a respective drain for receiving nutrient solution returned from the gullies 21. A level monitor 33 indicates when the level of nutrient solution 34 within the main tank 30 reaches a maximum desired level at which point a controller 35 commences operation of a pump 36 between the main tank 30 and the overflow tank 31, to ensure the desired level in the main tank is not exceeded. At the desired level, the inlets 32 are at least 1 meter above the level of nutrient solution 34 within the tank, with the inlets 32 arranged such that the return nutrient solution freefalls into the tank making a splash which acts to aerate the nutrient solution. Additionally, a mixing pump 36 is provided to provide additional aeration to the nutrient solution 34 within the tank 1, should this be required. The tank also has a sensor 37 for detecting the conductivity of the nutrient solution and a signal from the sensor 37 is used by the controller 35 to determine if the concentration of nutrients in the nutrient solution is sufficient. If it is not, then the controller 35 causes a nutrient supply unit 38 to dispense concentrated nutrients into the tank 30. The controller 35 can also open an inlet valve 39 to introduce additional water into the system as required, noting that the controller 35 may also operate the pump 36 in a reverse direction in order to reintroduce nutrients solution in the overflow tank 31 back into the main tank 30.

Although not shown, the above described system may also incorporate drip irrigation, in the form of an irrigation pipe carried by the grow pipe 17, to permit drip irrigation along the entire length of the gullies 21. When plants are initially laid out in the gullies it may be desirable to initially use drip irrigation to water and feed those plants, with return nutrients again being returned through the drains 27 to the reservoir 29. However, when the plants reach a certain stage of maturity a pump 40 of Figure 8 is actuated, taking nutrient solution 34 from the main tank 30 and suppling this to the grow pipes 17 at a desired rate to provide a steady flow of nutrient solution along each gully 21. The pump 40 will then normally be operated continually for the entire season.

A hydroponic crop growing system as described above has been found to be capable of growing tomatoes in the UK throughout the whole year and it has not been found necessary to sterilise the irrigation water supplied to the system, in contrast to the situation when substrate growing.

One embodiment of the present invention has been described above by way of example only, but it will be appreciated that many modifications may be made which fall within the scope of the invention as defined by the following claims.

Claims (22)

1. Claims 1. A hydroponic crop growing system using nutrient film technology for growing crops, the system comprising: a suspension assembly; a relatively rigid gutter suspended by the suspension assembly; a relatively flexible gully supported by the gutter and extending in a length direction of the gutter; multiple inlets at which a nutrient solution is introduced into the gully at a plurality of first positions along the gutter; and multiple drains where nutrient is drained from the gully at a plurality of second positions along the gutter, wherein: a plurality of runs are defined along the gutter between respective adjacent pairs of first and second position; the gradient of each run is between 1.27 and 1.35 percent; the gutter comprises at least four runs providing the gutter with a W-shape when viewed in side elevation; and wherein the system further comprises a nutrient reservoir for receiving nutrient solution from the multiple drains and a dispensing system for dispensing nutrient solution from the reservoir to the multiple inlets.
2. 2. A system as claimed in Claim 1, wherein the gradient of each run is uniform along the length of each run.
3. 3. A system as claimed in Claim 1 or 2, wherein the gutter, in cross section, has a substantially planar upper surface with a shallow depression in a central region.
4. 4. A system as claimed in Claim 3 wherein the shallow depression is less then 10mm deep.
5. 5. A system as claimed in any preceding claim, wherein the gutter is formed from multiple lengths of metal sheet.
6. 6. A system as claimed in any preceding claim, wherein the length of the gutter is over 100 meters.
7. 7. A system as claimed in any preceding claim, wherein the length of each run is less than 32 meters.
8. 8. A system as claimed in any preceding claim, wherein the gully is formed from polythene sheet.
9. 9. A system as claimed in any preceding claim, wherein the suspension assembly comprises two wires running parallel to the associated gutter, the two wires supporting respective sides of a gully.
10. 10. A system as claimed in any preceding claim, wherein the width of the gutter is over 300mm wide.
11. 11. A system as claimed in any preceding claim, wherein the reservoir comprises a tank with at least one return pipe entering the tank at a tank inlet, for returning nutrient solution to the tank from one or more drains, the return pipe entering the tank at a level above the level of nutrient solution in the tank, the system comprising control means to control the level of nutrient solution in the tank to maintain the level in the tank at or below a predetermined level below the tank inlet.
12. 12. A system as claimed in Claim 11, wherein the said tank is a first tank and the reservoir comprises a second tank for receiving overflow nutrient solution from the first tank.
13. 13. A system as claimed in Claim 11 or 12, further comprising a mixing pump to aerate the nutrient solution in a tank.
14. 14. A system as claimed in any preceding claim, wherein the gutter is 5 suspended above the ground by at least 700mm.
15. 15. A system as claimed in any preceding claim, further comprising a drip pipe suspended above the length of the gully by the suspension assembly.
16. 16. A system as claimed in any preceding claim, further comprising overhead high pressure sodium lighting and low level LED lighting arranged to be at a level intermediate the height of a crop.
17. 17. A system as claimed in any preceding claim, further comprising means for monitoring the nutrient levels in the nutrient solution, the monitoring means monitoring the conductivity of the nutrient solution and controlling the dispensing of concentrated nutrients into the nutrient solution in dependence thereon.
18. 18. A method of growing tomatoes comprising assembling a system as claimed in any preceding claim, placing tomato plants in the gullies and dispensing nutrients into the gullies.
19. 19. A method as claimed in Claim 18, further comprising drip irrigating the tomato plants until they reach a particular stage and then commencing the dispensing of the nutrient solution into the gullies at the multiple inlets.
20. 20. A method as claimed in Claim 19 wherein, once commenced, the nutrient solution is dispensed continuously until a crop is substantially ready to be harvested.
21. 21. A system as claimed in any one of claims 1 to 17 for growing tomatoes.
22. 22. Tomatoes grown by a system as claimed in any one of claims 1 to 17