The invention is related to a cultivation floor system on which plants are placeable, e.g. plants in plant containers or in soil blocks.

The invention is further related to a greenhouse provided with a cultivation floor system according to the invention and to a method for using a cultivation floor system according to the invention for growing plants, e.g. in plant containers, placed on the cultivation floor system. The invention is further related to a method for installing a cultivation floor system according to the invention and to a method for transporting plants, e.g. in plant containers, on the cultivation floor system.

EP2955996 discloses a cultivation floor system with a cultivation floor on which plant containers are placed, which cultivation floor system comprises a watertight basin, a water permeable structure in the basin and a watering installation. The water permeable structure comprises a top cloth which forms the top side of the floor and one or more water-retaining layers, for example of granular material.

Wheeled trolleys, e.g. Danish trolleys, see e.g. EP3421322, are used in greenhouses to transport objects, such as plant containers, to and from a cultivation floor. A fully loaded Danish trolley can weigh up to 450kg, which weight is distributed over the four wheels of the Danish trolley. These wheels are rather small, with a diameter of 125 mm and a width of 36 mm. When a Danish trolley is used on the cultivation floor of the known cultivation floor system the wheels may perturb the cultivation floor causing unevenness in the top side of the cultivation floor, e.g. by displacing the water-permeable structure, e.g. by displacing/locally compacting the granular material. Such unevenness may be small, e.g. some millimeters in depth, yet they may lead to uneven distribution of water to plant containers on the cultivation floor which in turn may lead to uneven plant growth.

A known solution to allow Danish trolleys onto the known cultivation floor system is to provide temporary trolley tracks on top of the cultivation floor, e.g. profile metal plates that are placed end-to-end on the top fabric and have a gutter in which the wheels of the trolley roll. The Danish trolley may be pushed over the trolley tracks and the weight of the (loaded) Danish trolley is carried and distributed by the trolley tracks. For example, the trolley tracks may be oriented in a longitudinal direction of an elongated cultivation floor. A downside of the known solution is that the trolley tracks need to be applied time and again as a temporary measure.

The invention provides an improved cultivation floor system which allows wheeled carts, e.g. a wheeled trolley, e.g. a Danish trolley, to be handled over the cultivation floor without causing unevenness in the top side of the cultivation floor system.

The invention provides a cultivation floor system according to claim 1.

The cultivation floor system on which plants, e.g. in plant containers or soil blocks, are placeable, comprises: a watertight basin comprising a bottom and a perimeter; a water permeable structure comprising at least a layer of a granular material, e.g. lava granules, filled in the basin; a water permeable top fabric which forms a top side of the cultivation floor system on which the plants, e.g. in containers or soil blocks, are placeable; an ebb/flood watering installation, which is configured to supply water so that water is available for the plants in the plant containers and comprises one or more irrigation lines embedded in the water- permeable structure,

The cultivation floor system further comprises a cultivation floor indentation resisting layer that is formed by adjoining and interconnecting perforated panels that are arranged between the permeable top fabric and the water-permeable structure. Herein the perforated panels are each provided with distributed perforations that allow water supplied via the irrigation lines to pass from the water-permeable structure through the perforated panels and through the permeable top fabric to plants, e.g. in containers or soil blocks, placed - in use - on the top fabric. Each panel has a solid cross section, a substantially flat upper side, and a substantially flat lower side, wherein the upper side and the lower side are substantially parallel. The perforations of the panels cover between 5% and 35% of the surface area of the upper side of the perforated panels.

The cultivation floor system - in use - serves for the cultivation of plants in plant containers or soil blocks that are placed on the permeable top fabric. Water is provided by the ebb/flood watering installation through the one or more irrigation lines embedded in the water- permeable structure. The water permeable structure allows for even distribution of the water to the cultivation floor. The permeable top fabric provides a top side for placing plants, e.g. in plant containers or grown on soil blocks, thereon and protects the water-permeable structure. The cultivation floor system allows for precise plant growth by controlling the amount of water each plant, e.g. in a plant container or soil block, on the cultivation floor receives.

The cultivation floor system of the invention is provided with an indentation resisting layer which is provided between the permeable top fabric and the water-permeable structure. By providing the indentation resisting layer above the water-permeable structure the water- permeable structure, e.g. the granular material, is not perturbed by carts, e.g. wheeled trolleys, e.g. Danish trolleys, that are handled on the cultivation floor. As a result the cultivation floor is less likely to, or will not, develop unevenness as a result of handling carts thereon. The panels of the indentation resisting layer have a panel shape having parallel upper and lower sides. The perforations cover between 5% and 35% of the surface area of the upper side of the panel. Thus the panels allow water to pass through, while simultaneously providing support for carts placed thereon.

The perforated panels are suitable to carry the weight of Danish trolleys handled on the cultivation floor system. The perforated panels are further suitable to allow sufficient water to pass between the water permeable structure and the permeable top cloth through the perforations therein. However, an increase in perforations in the perforated panel, measured as a fraction of surface area of the perforated panel, may weaken the perforated panel, and thus reduce the ability of the perforated panel to carry the weight of carts thereon. It is found that a suitable amount of water may pass through the perforated panels, while simultaneously the perforated panels may carry the weight of e.g. Danish trolleys thereon, when the perforations in the perforated panels cover between 5% and 35% of the surface area.

The top side of the permeable top fabric is configured for placing plant containers thereon. By placing the indentation resisting layer below the permeable top fabric, the top side of the cultivation floor is not, e.g. partially, covered by the indentation resisting layer. By placing the indentation resisting layer below the permeable top fabric the surface area suitable for placing plant containers thereon is not reduced.

Placing the indentation resisting layer below the permeable top fabric also allows portions of the cultivation floor to be provided with the indentation resisting layer, and other portions of the cultivation floor to not be provided with the indentation resisting layer. This may reduce monetary and building costs of constructing the cultivation floor as fewer perforated panels may have to be provided. An advantage of the invention over the use of, e.g., trolley tracks is that the portion of the cultivation floor that may be used for placing plant containers is increased and the invention increases the efficiency of the cultivation floor system for growing plants

A further advantage of the invention is that the cart, e.g. the Danish trolley, is not forced to move along trolley tracks, which increases the freedom of movement of the cart on the cultivation floor system.

The indentation resisting layer is formed by adjoining and interconnecting perforated panels, wherein each panel is provided with distributed perforations that allow water to pass through the indentation resisting layer between the permeable top fabric and the water-permeable structure. The distributed perforations may be provided on the panels in a variety of patterns.

In practical embodiments, each perforation has a maximum dimension in the upper side of the panel that is at most 30 mm, preferably at most 20 mm. This dimensioning of the perforations in the panels assures that the (hard tire) cart wheels do not sink into the perforations when driving over the top fabric. This may avoid undue stress on the fabric along the edge of the perforation when driving a cart over the floor and may avoid locally indenting the fabric into the perforations in the panel.

As preferred, the panels make up a path or walkway, effectively under the top fabric, over which carts may travel without the wheels of the carts locally indenting the floor. The top fabric is at the same height throughout the floor, so not locally elevated or recessed where the panels form the walkway.

For example, the panels form a path or walkway that makes up at most 20% of the surface of the floor. In practice, this allows for a path that is sufficient wide to be driven over by a cart, or two carts passing each other, whilst leaving the majority of the floor without the provision of panels. The location of the walkway may be made visible by colored lines or the like in/on the top fabric and/or by other walkway indicia, e.g. indicators at the side of the floor where the walkway starts.

Preferably, each perforated panel has a density higher than 1000 kg/m ³ such that the perforated panel does not float, e.g. the perforated panels do not float when the cultivation floor is flooded by the ebb/flood watering system. In embodiments the perforated panels may have a density that is slightly lower than that of water. In these embodiments, preferably, the perforated panels and/or the top fabric are anchored such that the perforated panels do not float on water provide by the watering installation.

In an embodiment the perforated panels are placed directly on top of a granular layer filled in the basin, so with granular material in direct contact with the perforated panels.

In an embodiment, a water permeable protective film is placed between the water permeable structure and the cultivation floor indentation resisting layer. This protective film prevents the granular material from entering into the perforations of the perforated panels and thus prevents the perforations from becoming blocked by the granular material.

In an embodiment, a water distribution cloth may be provided between the water permeable structure and the top fabric to better distribute water over the cultivation floor system.

Preferably, the perforated panels are constructed from a material that does not unduly expand nor shrink due to temperature changes in a temperature range wherein the cultivation floor system is used, e.g. in a temperature range between 0 °C and 50 °C. For example, the panels are made of ABS or a fibre-reinforced plastic, e.g. fibre-reinforced PE or PP.

Preferably, the perforated panels do not chemically react with fertilizers, plant protection products, cleaning products or other products which are commonly used in the cultivation of plants. For example, the panels are made of ABS or fibre-reinforced plastic, e.g. fibre- reinforced PE or PP.

For example, the perforated panels have a thickness between 2 mm and 8 mm, for example between 3 mm and 5 mm. Due to the fairly limited thickness, the panels, even when made of plastic as preferred, will not unduly absorb heat which could lead to an undesirable impact on the temperature just above the top fabric, which might affect plant growth and/or formation of algae and/or cause an undesirable variation compared to plants growing on the same floor yet not above the perforated panels.

For example, the perforated panels are made of polypropylene with a fiber, e.g. a fiber glass, reinforcement or from a polyethylene reinforced with a fibre. Preferably herein, the panel has a density higher than 1000 kg/m3 such that the perforated panel does not float. For example, the thickness is between 2 mm and 8 mm, for example between 3 mm and 5 mm. For example, a distance between adjacent perforations in a panel may be between 3 and 5 cm, for example 4 cm.

For example, the perforated panels may have dimensions of 25 cm by 25 cm or larger, e.g. at most 40 cm by 40 cm, e.g. when the panel is to be injection molded.

The indentation resisting layer allows carts, e.g. Danish trolleys, to be handled over a portion of the cultivation floor where the perforated panels are provided. The weight of the cart is distributed by the perforated panels over a greater surface area of the cultivation floor system such that the water-permeable layer, e.g. the granular material, is not perturbed, e.g. indented, by the cart, which may cause unevenness in the top side of the permeable top fabric.

The indentation resisting layer further still allows the ebb/flood watering system to provide water to the top side of the cultivation floor system and to remove water from the top side of the cultivation floor system by allowing water to pass through the perforations of the panels.

In embodiments, the perforated panels may have a density that is higher than 1000 kg/m3, e.g. higher than the density of water, such that the perforated panels do not float on water, e.g. they do not float on water provided by the ebb/flood watering installation. An advantage of this is that the perforated panels are less likely to move during operation of the ebb/flood watering installation.

The cultivation floor system of the invention may be used in any situation wherein a cultivation floor may be used. For example, the cultivation floor system may be used in a greenhouse. For example, the cultivation floor system may be used in an outdoor cultivation area for growing plants, e.g. in plant containers.

In an embodiment, the cultivation floor system also comprises one or more wheeled carts, e.g. trolleys, configured to transport plants, e.g. in plant containers or soil blocks, onto or from the floor, wherein - in use - the wheels ride over the top fabric.

The inventive cultivation floor system may also temporarily be used for other activities than horticultural cultivation of plants, e.g. for the temporal use of storage of equipment/goods. The indentation resistant panels allow for such increased functionality of the floor. In an embodiment, the cultivation floor system further comprises a perforated film placed under the permeable top fabric, e.g. between the permeable top fabric and the cultivation floor indentation resisting layer or between the cultivation floor indentation resisting layer and the water-permeable structure, which perforated film is made of an impermeable film material which is provided with distributed perforations. The distributed perforations of the perforated film may be aligned with the perforations of the perforated panels, as is preferred. In using the cultivation floor system, water may remain in the water permeable structure, e.g. in the granular material, even when the water has been drained by the watering installation. The remaining water may evaporate increasing humidity above the cultivation floor, undesirably changing the growth conditions of plants, e.g. in plant containers, on the cultivation floor. Additionally, the evaporated water may cause the permeable top fabric to remain moist, which may lead to the growth of algae thereon. The evaporation of remaining water may be reduced by the presence of the perforated film, thus alleviating the described problems.

In an embodiment, each perforated panel has a solid cross section, a substantially flat upper side, and a substantially flat bottom side, wherein the upper side and the bottom side are substantially parallel.

In an embodiment, the upper side of the perforated panels are roughened and/or grooves are provided on the bottom side of the perforated panels e.g. grooves adjoining the perforations so as to allow air to escape from underneath the panels when water level rises within the permeable structure. By providing a roughened upper side of the perforated panel, the permeable top fabric provided thereon is less likely to move as a result of an increased friction between the perforated panels and the permeable top fabric.

The bottom side of the perforated panels may be provided with grooves, e.g. parallel grooves, e.g. grooves that extend from or between the perforations in the perforated panels. The grooves may allow air to escape easier towards the perforations when water is supplied to the basin for flooding of the floor. This, for example, reduces the risk of bulging and/or movement of the panels due to an accumulation air under the perforated panels.

In embodiment, the perforated panels are made from a plastic material, e.g. the perforated panels are made from ABS (Acrylonitrile butadiene styrene) or (glass) fibre-reinforced PE (polyethylene) or PP (polypropylene).

In embodiments, e.g. of plastic, the panels each have a density higher than 1000 kg/m3.

Plastic materials, may have desired characteristics such as having a density higher than that of water, while simultaneously being easy and cheap to manufacture to be used in the indentation resisting layer. This density can, for example, be achieved through the use of or (glass) fibre-reinforced PE (polyethylene) or PP (polypropylene), e.g. when injection molding the panels.

In embodiments, the panels have a density less than 1000 kg/m3, e.g. between 950 and 1000 kg/m3. Floating of such panels may be countered by the top fabric being secured, e.g. at the perimeter of the basin, so that the panels are held by the fabric. Other anchoring means may also be provided to counter floating of the panels, e.g. anchoring means embedded in the granular layer.

ABS as material for the panels has the advantage that ABS allows for transport of heat and/or cold between the water permeable and the plants due to material properties thereof. The perforated panels may be manufactured from new or recycled ABS.

When the panels are made of (glass) fibre-reinforced PE (polyethylene) or PP (polypropylene), the polymer may be a recycled polymer.

In an embodiment, the perforated panels extend under only a portion of the surface area of the permeable top fabric, for example at most 20% of the surface area. By covering sufficient surface area of the top side of the permeable top fabric, the perforated panels allow the use of carts on a sufficiently large portion of the surface area. Simultaneously construction cost may be reduced by covering a smaller surface area of the cultivation floor. It is found that by covering at most 20% of the surface area of the cultivation floor carts can be used to sufficiently reach the whole cultivation floor area. For example, the indentation resisting layer may be provided in a strip or walkway in a longitudinal direction of the cultivation floor, e.g. wherein the walkway is 2 meters wide, e.g. wherein the strip extends the full length of the cultivation floor.

In an embodiment, the perforated panels are injection molded and each have a length between 20 cm and 40 cm and/or a width between 20 cm and 40 cm and/or a thickness between 2 mm and 8 mm, e.g. about 3 - 5 mm. It was found that perforated panels of these dimensions allow for an advantageous embodiment of the cultivation floor system. The panels are sufficiently thick to carry the weight of the carts, while not being so thick that the water does not pass through the perforations. Perforated panels having these dimensions are easy to manufacture and handle, e.g. during installation of the cultivation floor system. In an embodiment, the perforations of the perforated panels are circular and have a diameter between 2 mm and 30 mm, for example between 10 mm and 20 mm, e.g. about 15 mm. It is found that perforations of these diameters allow sufficient water to pass through the perforated panels, while not reducing the functionality of the panels.

For example, with a diameter of at most 30 mm, preferably at most 20 mm, the trolley wheels of a loaded trolley will ride over a perforation without sinking into it. The preferred range of diameters, may also be beneficial in view of the general structural strength of the perforated panels, e.g. made of plastic. Generally, too large and/or too many perforation may weaken the panel, so that the wheel load is not effectively distributed, and the perforated panels may not support a cart effectively. Perforations of differing diameters may be provided in a single perforated panel.

In another embodiment, the perforations of the perforated panels are non-circular, e.g. have an elliptical, rectangular, square, (arched) slit shapes, or irregular shape. It is found that circular perforations allow a membrane of water to form over the perforation thus reducing the effectiveness of the perforation in allow water to pass. This may result in areas of the top fabric that are directly above the perforations being wetter. The membrane of water is less likely to form when the perforations are not circular, thus resulting in a better functioning system. For example, a typical dimension of the non-circular perforations lies between 2 mm and 30mm, for example between 10 mm and 20 mm, e.g. about 15 mm.

For example, wherein the perforations of the perforated panels are non-circular in shape, e.g. square or rectangular, and each have a surface of between 4 mm ² and 700 mm ² , e.g. between 70 mm ² and 300 mm ² , e.g. about 175 mm ² .

In an embodiment, the perforations of the perforated panels are provided in the perforated panels by punching. The perforated panels may be manufactured, e.g. by injection molding, or bought without perforations and the perforations may be provided by punching. The material that is removed from the panel by punching may be reused in the construction of additional panels.

In an embodiment, the perforated panels are manufactured by injection molding, e.g. the perforations being formed in the injection molding process. The panels may be manufactured with the perforations directly during injection molding or the perforations may be provided at a later stage, e.g. by punching. In an embodiment, the perforations in the perforated panels taper from the smallest diameter in the top surface of the panel to the largest diameter in the bottom surface of the panel.

In an embodiment, the perforated panels are connected via panel connection means, e.g. which panel connections means are integrated with side edges of the panels. The panel connection means allow adjoining perforated panels to be connected to each other increasing strength of the indentation resisting layer. For example, the panel connection means may prevent adjoining panels from moving relative to each other when a cart is handled on the cultivation floor. The panel connection means may comprise male and female parts, wherein, for example, the male parts are provided on one perforated panel and the female parts are provided on an adjoining panel.

In an embodiment, the irrigation lines have openings along their length, and the watering installation is configured for water to flow from the one or more irrigation lines to flood the basin to a level above the permeable top fabric and to relief the water from the basin.

The invention further relates to a greenhouse provided with a cultivation floor system according to the invention. The cultivation floor system is advantageously used in a greenhouse, wherein one or more cultivation floors and one or more cultivation floor systems may be provided.

In an embodiment of the method plants or plant containers are transported onto and/or from the floor by means of a cart, e.g. a wheeled trolley, having wheels engaging the top fabric, the cultivation floor indentation resisting layer formed by the adjoining and interconnected perforated panels avoiding indentation due to the wheels of the trolley.

The invention further relates to a method for growing plants, e.g. in plant containers, preferably in a greenhouse, wherein use is made of a cultivation floor system according to the invention. The cultivation floor system may be used to grow and cultivate plants, e.g. in plant containers placed on the cultivation floor by watering the plants and by performing other acts related to the growth and cultivation of plants, e.g. fertilizing the plants in the plant containers.

The invention further relates to a method for installing a cultivation floor system comprising a cultivation floor configured for placing plants, e.g. in plant containers or soil blocks, thereon, which method comprises:

- providing a watertight basin having a bottom and a perimeter with a top edge; - placing one or more irrigation lines in the basin, which irrigation lines preferably, each have a multitude of openings along their length for passage of water through said openings,

- connecting an ebb/flood watering installation, e.g. an ebb/flood water supply and discharge system including a water pump, to the one or more irrigation lines;

- filling into the basin one or more layers of loose granular material, e.g. lava granules;

- possibly, compacting the one or more layers of loose granular material so as to provide permeable granular material structure in the basin, wherein the one or more irrigation lines are embedded in the granular material structure,

- providing a substantially horizontal top surface of the compacted permeable granular material at a level at or, preferably, below the top edge of the perimeter of the watertight basin,

- covering a portion of the top surface of the compacted permeable granular material by an indentation resisting layer with adjoining and connecting perforated panels that are each provided with distributed perforations that allow water to pass from the water-permeable structure through the perforated panels to the permeable top fabric, wherein each panel has a solid cross section, a substantially flat upper side and a substantially flat lower side, wherein the upper side and the lower side are substantially parallel, and wherein the perforations in the perforated panels cover between 5% and 35% of the surface area of the upper side of the perforated panels,

- arranging a water-permeable top fabric, e.g. a (woven) fabric or a mat, over the indentation resisting layer and any remaining portion of the top surface of the compacted permeable granular material that is not covered by the indentation resisting layer.

The invention also relates to the use of carts, e.g. trolleys, in combination with a floor system as described herein, wherein the carts ride over the top fabric and are used for conveyance of plants to and/or from the floor, e.g. in plant containers or soil blocks.

The invention will be explained below with reference to the drawing in which:

Fig. 1 shows a cultivation floor system on which plant containers are placed having the indentation resisting layer;

Fig. 2 shows a cross section of a cultivation floor system having the indentation resisting layer; and

Fig. 3 schematically shows a perforated panel for use in a cultivation floor system.

Figure 1 shows a cultivation floor system 1 on which plant containers 2 are placed. The cultivation floor system comprises a watertight basin 3. In the basin 3, a water-permeable structure 5 and a permeable top fabric 4 are present. Plant containers 2 are placed on the top side of the permeable top fabric 4.

The water permeable structure 5 comprises a layer of granular material. The granular material may be, for example, of lava granules.

The granular material may also be composed of, or contain, crushed stone, (natural) gravel, etc. Crushed stone often has an angular and jagged edge that occurs during the crushing process. Naturally formed gravel, typically has a smooth texture and surface because of being exposed to the effects of running water. If it is crushed, natural gravel loses its smooth rounded texture and becomes crushed stone. It is noted that crushed stone is often referred to as gravel.

Furthermore, an ebb/flood watering installation is provided which is configured for supplying water, so that water is available to the plants in the plant containers 2. The watering installation comprises one or more irrigation lines 6 in the basin 3, which irrigation lines 6 have several outflow openings along their length which make it possible for water to flow out of the one or more irrigation lines 6, wherein the one or more irrigation lines 6 are embedded in the water-permeable structure 5.

In this embodiment, the ebb/flood watering installation further comprises a water storage 7, for example a storage pond or an underground water storage, from which water can be pumped by means of a pump 8 in order to supply water to the basin 3, for example until a water level above the permeable top fabric 4 is achieved. Once this “flood situation” has lasted sufficiently long, the water is allowed to flow away to the storage 7. A valve assembly 9 may be provided in order to control the desired supply of water to the basin and discharge from the basin 3. In a possible variant, the water storage 7 is above the level of the cultivation floor, so that the difference in height in fact supplies the pump action for the water supply to the cultivation floor and no separate pump is necessary in the supply to the cultivation floor. Optionally, a pump is provided, e.g. in the return flow to the water storage.

The top fabric 4 is water-permeable, e.g. having a relatively high porosity and small pores.

Preferably, the top fabric 4 is constructed from a (woven) material that does not unduly expand nor shrink due to temperature changes in a temperature range wherein the cultivation floor system 1 is used, e.g. in a temperature range between 0 °C and 50 °C. Preferably, the top fabric 4 does not chemically react with fertilizers, plant protection products, cleaning products or other products which are commonly used in the cultivation of plants.

Preferably, the top fabric 4 is woven, for example from suitable synthetic yarn(s).

In embodiments, the pores between the yarns of the top fabric 4 are relatively small.

The top fabric 4 preferably is, preferably, UV-resistant, and also wear-resistant, for example so that it is suitable to be driven over by trolleys, e.g. Danish trolleys.

The cultivation floor system 1 further comprises an indentation resistant layer 10, which is provided below the permeable top fabric 4, here directly between the top fabric and granular material filled in the basin.

The indentation resisting layer 10 is formed by adjoining and interconnecting perforated panels 11 , wherein the perforated panels 11 are each provided with distributed perforations 12 that allow water supplied via the irrigation lines 6 to pass from the water- permeable structure 5 through the perforated panel 11 to the permeable top fabric 4. The water rises through the fabric 4 and so reaches the plants 2 that are placed in containers ort soil blocks on the fabric. When the plants have been watered sufficiently, the ebb-phase is triggered by relieving water from the basin, commonly via the same lines 6.

Each perforated panel 4 has a solid cross section, a substantially flat upper side, and a substantially flat bottom side, wherein the upper side and the bottom side are substantially parallel.

In this embodiment the perforated panels 11 each have a density higher than 1000 kg/m ³ .

The perforated panels 11 are not individually shown in figure 1.

As can be seen in figure 1 the indentation resistant layer 10 in this embodiment is not provided over the whole surface area of the cultivation floor. As preferred, the panels 11 make up a path or walkway, effectively under the top fabric 4, over which carts may travel without the wheels of the carts locally indenting the floor. The top fabric 4 is at the same height throughout the floor, so not locally elevated where the panels 11 form the walkway. For example, the panels 11 form a path or walkway that makes up at most 20% of the surface of the floor. In practice, this allows for a path that is sufficient wide to be driven over by a cart, or two carts passing each other, whilst leaving the majority of the floor without the provision of panels. The location of the walkway may be made visible by colored lines or the like in/on the top fabric and/or by other walkway indicia, e.g. indicators at the side of the floor where the walkway starts.

Placing the indentation resisting layer 10 below the permeable top fabric 4 allows portions of the cultivation floor to be provided with the indentation resisting layer 10 as in figure 1, and other portions of the cultivation floor to not be provided with the indentation resisting layer 10. Both portions are covered by the fabric 4. This may reduce monetary and building costs of constructing the cultivation floor system 1 as fewer perforated panels 11 may have to be provided. The indentation resisting layer 10 allows carts to be handled over a portion of the cultivation floor where the perforated panels 11 are provided.

By providing the indentation resisting layer 10 above the water-permeable structure 5, directly on top of the granular material, the water-permeable structure 5, here the granular material, is not perturbed by carts, e.g. Danish trolleys, that are handled on the cultivation floor. As a result the cultivation floor is less likely to develop , or will not develop, unevenness as a result of handling carts thereon.

The indentation resisting layer further still allows the ebb/flood watering system to provide water to the top side of the cultivation floor system and to remove water from the top side of the cultivation floor system by allowing water to pass through the perforations 12 of the panels 11.

The perforated panels 11 have a density that is higher than the density of water, thus the perforated panels 11 do not float on water, e.g. they do not float on water provided by the ebb/flood watering installation. An advantage of this is that the perforated panels are less likely to move during operation of the ebb/flood watering installation. In embodiments the perforated panels may have a density that is slightly lower than that of water. In these embodiments, preferably, the perforated panels and/or the top fabric are anchored such that the perforated panels do not float on water provide by the watering installation.

Figure 2 shows a cross section of a cultivation floor system 1 having the indentation resisting layer 10 provided below the permeable top fabric 4 and below an impermeable film 15. The indentation resisting layer 10 or walkway is provided over a portion of the cultivation floor surface area. This makes a portion of the cultivation floor on the left side of the figure suitable for handling of carts and a portion of the cultivation floor on the right side of the figure unsuitable for handling of Danish trolleys.

In this case, the top fabric 4 is situated directly on top of the impermeable film 15, which film 15 containing perforations to allow water to pass through. The distributed perforations in the impermeable film 15 may be provided in such a manner that the film reduces the free evaporation surface of water from the water-retaining layer 5 preferably by at least 50%, more preferably by at least 90%.

The impermeable film 15 is closed as such, and therefore does not allow water or water vapour to pass, except at the location of the perforations in said film 15. In this way, the film 15 forms an, albeit imperfect, barrier to water, as it were, which, due to the (usually heated) climate in the greenhouse (or optionally due to heating in the cultivation floor itself) will want to evaporate and rise up through the permeable structure 5 and the permeable top fabric 4. Water will in particular evaporate in areas of the cultivation floor where the indentation resisting layer 10 is not provided.

The impermeable film 15 significantly reduces the free evaporation surface. As a result thereof, water which has remained behind in the water permeable structure 5 can evaporate much less readily. The size of the perforations in the impermeable film 15 is, preferably, chosen to be such that the perforations do not impede a possible through-flow of water in an ebb/flood watering installation. The or some of the perforations in the impermeable film 15 may be aligned with the perforations 12 provided in the perforated panels 11.

In an embodiment ,the impermeable film 15 may only be provided on portions of the cultivation floor surface area where the indentation resisting layer 10 is not provided.

In another embodiment, the film 15 is absent all together.

An example of a perforated panel 11 for use in the cultivation floor system 1 is schematically shown in figure 3.

The perforated panel 11 shown in this figure may be made from ABS or from (glass) fibre- reinforced plastic, e.g. PE (polyethylene) or PP (polypropylene). The perforations 12 in the perforated panels 11 cover between 5% and 35% of the surface area of the perforated panels 11 .

Figure 3 shows an upper side of the perforated panel 11 which may be roughened to increase friction between the perforated panel 11 and a permeable top fabric 4 which is placed on top of the perforated panel 11 . This prevents the permeable top fabric 4 from sliding over the perforated panel 11 , for example when a Danish trolley is handled thereon.

Figure 3 further shows panel connection means 13, which are embodied as hooks which may connected with holes (not shown) provided in adjoining perforated panels 11. The panel connections means 13 are integrated with side edges of the perforated panels 11 , e.g. during manufacturing of the panel 11.

For example, the panel 1 has outwardly extending hook members along each of its side edges, e.g. elongated hook members with upward and downward directing hook portions so that adjacent panels hook onto one another.