The invention relates to a plant growing device and a method to grow plants by applying the same.

Almost all known devices for use in agricultural systems comprise for irrigation the since long used system of drainage in an open space. The well-known hydroponic system and especially the Nutrient Film Technique (NFT) has various disadvantages as a high chance on the spread of diseases, especially of the roots and the high maintaining costs of the drainage system. Furthermore, upon using such a system it is not possible to regulate fertilization.

An example of a non-circulating hydroponic drainage plant-growing system has been disclosed in US patent 5,533,299 solving some but not all of these problems. In US patent 8,448,379 a totally concealed clean room vegetable factory but also the use of an overflow drain system has been disclosed.

Furthermore, by applying a drainage system the use of a 100 % organic nutrient solution is generally not possible. Once the water returns via the drainage system to the water tank several problems arise with the control of the electrical conductivity (EC) and the pH.

- Relating to the disorder of the EC: an EC meter just records the mineral part of the solution. The NFT will supply water with nutrient to the plants in accordance with the EC as measured. However, a part of the organic nutrient will not be broken down into inorganic matter. This means that the computer will give a signal to inject more water with nutrient than beneficial and a great volume of organic matter not yet mineralized will be accumulated. As a consequence, at the end an EC disorder will appear in the nutrient solution.

- Concerning the pH: all water recycled in horticulture returns with a high value of pH of above 7.5. To bring this parameter back to the optimal value of 5.8 an extremely high amount of the weak organic acid source will have to be used to achieve this pH value.

Furthermore, when we use organic nutrients in a recycling system, water has to be aerated continuously, otherwise organic matter is broken down by anaerobic bacteria instead of by aerobic bacteria. In that case unwanted microorganisms will be reproduced and plants roots will be susceptible to get sick caused as for instance by the plant parasite Pythium.

It is an object of the present invention to provide a plant growing device allowing the possibility to make use of organic feed without the high costs of maintenance of the drainage system and without the drawbacks as mentioned related to disorder of the EC, the high pH and the susceptibility to plant sicknesses. It is a further object of the present invention to provide a method to grow plants using said system.

The present invention provides a device of the type stated in the preamble comprising:

a container for feed in water for the plants (2), a container for fertilizer (2a), a container for water (2b), a container for acid (2c) and optionally a mixer;

one or more growing trays (3) for one or more plants in a substrate;

a tube (6) from said container for feed in water for the plants (2) to the one or more growing trays (3) for the transport of said feed to the plants;

means (7) to condensate the water vapour leading to

a tube (8) to lead back the condensed water to the container for water (2b).

Preferably, the one or more growing trays (3) comprise(s) one or more water permeable separate holders (5) for one or more of the plants and passageways (4) along the holders (5). The trays may be placed above and under as well as besides each other. Tube (6) for the transport of the feed in water may be divided in more for instance lateral tubes leading to more trays. More preferably, one or more of the plants are in a pot, generally with substrate. Especially, the means (7) to condensate essentially consists of a tube at a temperature of about 20 - 22°C, more preferably about 21°C. Means common for the growing of plants like a pump suitable to pump the water and lamps to provide artificial light and heat will generally be present as well. The bottom of the holders (5) will preferably be open with one or several holes which will facilitate the water uptake from the tray (3) and by the substrate in the pot of the plants by capillarity.

Furthermore, the present invention provides a method to grow plants by:

applying a plant growing device (1) according to the present invention by

filling the container for fertilizer (2a) with fertilizer, the container for water (2b) with water, the container for acid (2c) with acid, and the container for feed in water for the plants (2) filling with water, fertilizer and optionally acid from the respective containers, optionally with mixing; pumping the feed in water through tube (6) to the one or more growing trays (3) optionally by an inlet water pipe and for instance through a passageway (4), so that the plants suck the water by capillary force;

allowing the water transpired and evaporated to condensate on means (7) and using optionally artificial light, especially by lamps.

If holders (5) are present the feed in water will generally not only flow along the holders (5) through the passageways (4) but under the holders as well. The plants will preferably 100% artificially be illuminated by lamps, more preferably about 60 - 70% in the night and about 30 - 40% during the day, mainly to avoid peak energy consumption. The water transpired and evaporated originates from its different sides: water uptake by plants which is released by transpiration; water evaporated from substrate in case it is wet and the small water film between the growing trays which remain after the irrigation. The water will especially evaporate due to the heat released by the lamps.

Preferably the method to grow plants according to the invention comprises filling the container for fertilizer (2a) with fertilizer, the container for water (2b) with water and optionally a container for acid (2c) with acid, and the container for feed in water for the plants (2) with water, fertilizer and optionally acid from the respective containers. Furthermore, the nutrient solution will preferably be added to the irrigation system based on the electrical conductivity (EC) value of the substrate to avoid a salinization. The EC measurement generally takes place two times a week. The organic feed will preferably be diluted until the optimal EC substrate at 20 °C of 0,4 - 0,8 dSm during the first 10 days, and from 0,8 - 1,4 dSm during the next 10 days of maturity has been reached. This means that if the EC value is too high only solution without feed may be applied.

In a special embodiment container (2a) used to fill the container for feed in water (2) comprises organic fertilizer, more preferably worm manure. In a special embodiment part of said organic fertilizer, especially worm manure is diluted as a compost tea or compost brewery aerated in an aerobic condition for more than 24 hours as described in US patent 6,649,405. The other part of said organic fertilizer especially worm manure is applied as such. The pH of the solution as supplied will generally be maintained at a pH of about 5,8 - 6 using an organic acid source. Especially, container (2b) used to fill the container for feed in water (2) comprises an organic acid as citric acid or acetic acid.

In fact, contrary to the plant growing devices from the prior art this device according to the invention does not contain a drainage system. This gives a lot of advantages like:

it makes the application of fertilizer which is 100 % organic on a large scale possible as for instance the best and cheap organic manure like worm manure costs savings related to the pipe installation: a drainage system has a complex structure with a filter installation and disinfecting equipment what may be avoided

the consumption of water is extremely low when a drainage system may be avoided

the harvesting cycle is generally shorter if a device is used according to the invention compared to said cycle upon using a drainage system

no chance on contamination with fecal bacteria because first of all the water will be supplied by capillarity and not by foliar spraying and secondly because the washing process in the prior art drainage system is the moment that the plants may be infected.

The water used during the irrigation system originates from:

- water sucked up by the plants and released by transpiration,

- water evaporated from substrate present in the pots,

- between growing holders there will be a small water film which remains after the irrigation; this water will be evaporated as well due to the heat released by the lamps.

In other words: the irrigation system of the water is a recycling process. The volume of water is collected as vapour by the cooling panel of a tube, at a temperature of about 20 - 22 °C; the water source comprises the water evaporation of the plant, the humidity of the substrate saturated after the irrigation and the water film residue of the bed which supports the growing holder.

After the seedling process preferably the tray (3) and (from there) the holders (5) must be irrigated from the seedling machine, in order to initiate the water transport possible by capillarity due to the cohesion tension of water molecules. The process will help the capillarity water movement through the porosity of the substrate. Water with the feed solution will be supplied to the growing tray (3) by flood irrigation. The amount and frequency will be calculated based on a hydric necessity and water holding capacity of the substrate. As substrate any kind of growing media for horticulture like for instance Cocos fibre or peat may be used. As indicated, a substrate may be used in a pot but a feed bed like BioStrate ^® Felt from Grow-Tech LLC may be applied as well.

The plant growing device according to the invention may especially solve the problems with the hydroponic device applied to baby salad, but may advantageously be applied to for instance tomato, pepper, beans, melon and so on as well.

Throughout this patent right the words 'feed' and 'nutrient' have

interchangeably been used.

The present invention is further elucidated on the basis of the following drawings of a preferred embodiment with plants in a pot:

Figure 1 : Schematic front view of the plant growing device (1) with an oblique top view of the growing tray (3):

a container for feed in water for the plants (2), a container for fertilizer (2a), a container for water (2b) and a container for acid (2c); a growing tray (3) for plants; a tube (6) for the transport of the feed to the plants via the tray (3); condensation means (7) and a tube (8) to lead back the water to the container with water (2b).

Figure 2: Schematic oblique top view of a growing tray (3):

holders (5) hold each plant in a pot leaving passageways (4) for the feed in water for the plants.

The figures are predominantly schematic and not drawn to scale. Corresponding parts are designated in the figures with the same reference numerals.

The holders (5) will usually be made of biodegradable material with holes (not shown in the figures) making them water permeable so that the plants may suck up the water by capillary force.

Although the invention has been elucidated above with reference to an embodiment and application, it will be apparent that the invention is by no means limited thereto. On the contrary, many other variations are possible within the scope of the invention for the person with ordinary skill in the art.