Description

The present invention relates to a seedling box having openings for the drainage of surplus irrigation water on at least one side wall of the box. The invention further relates to the use of such a seedling box for growing young plants, especially young rice plants, and to a method for growing young plants, especially young rice plants, which method comprises sowing seeds, specifically rice seeds, into or onto a growth medium contained in such a seedling box and growing the plants in this box until they reach a predetermined size.

Sowing rice seeds and growing seedlings in seedling boxes (also called nursery boxes) is a common rice cultivation practice, especially in Japan. The seedling boxes are gen- erally placed in a greenhouse or in a protected place until the seedlings reach a specific height. Then the young plants are transplanted, for instance into a paddy.

Common rice seedling boxes are rectangular containers or trays of some centimetres of height and with an open upper side. Generally, the bottom side is punched, i.e. it has several openings for the drainage of surplus irrigation water. The box contains a growth medium (generally soil) wherein the rice seeds are sown and grow.

During the last years it has become common practice to provide the box with a layer containing agrochemicals or to treat the growth medium or the seeds with agrochemi- cals, especially pesticides such as insecticides and fungicides.

As the common seedling boxes are punched at the bottom side, surplus irrigation water is drained through the bottom openings and entrains a part of the agrochemicals present on or in the growth medium. As a consequence, the soil beneath the seedling box becomes contaminated with the rinsed-out agrochemicals. This is problematic for farmers who, after transplanting the young rice plants, are desirous to plant instantly other crops on the place where the seedling boxes were placed beforehand: As many pesticides are only approved for rice, the farmers are not allowed to plant other crops in the contaminated place. The farmers are recommended in this case to wait for some time until the degradation of the agrochemicals, which, however, is of course associated with economic disadvantages.

Another problem is that soil-borne diseases, such as soil-borne fungi or bacteria, emerging in the soil on which the seedling boxes are placed can migrate via the bottom openings into the seedling box and infect the growth medium and/or the seeds or young plants.

Moreover, due to leakage, agrochemicals are wasted.

Thus it was an object of the present invention to provide a seedling box which does not present the disadvantages of the seedling boxes of the prior art. In particular, the seedling box should avoid or at least reduce the contamination of the soil beneath the seedling box with agrochemicals present in it. Moreover the seedling box should also re- duce the consumption of irrigation water and to reduce the quantity of required agrochemicals. Furthermore, the infection with soil-borne diseases should be avoided or at least reduced.

The object is achieved by a seedling box having openings for the drainage of surplus irrigation water on at least one side wall of the box. Specifically, the seedling box is a rice seedling box, but of course it can be used for other plants, too.

The plants may for example be cereals or ornamental plants. Cereals are the cultivated forms of grasses (Poaceae) and include for example wheat (inclusive spelt, einkorn, emmer, kamut, durum and triticale), rye, barley, rice, wild rice, maize (corn), millet, sorghum, teff and oats. Preferably the plant is rice.

Preferably, the box has no openings on the bottom.

Opening" means hole or perforation in the wall.

The relative terms "side walls", "upper side" (also termed "top") and "bottom" (of the seedling box) are to be understood as follows: A side wall is a wall essentially parallel to the main growing direction of the plant. "Essentially parallel" means that the devia- tion from the perfectly parallel direction is less than 45°, more preferably less than 30°, even more preferably less than 20° and in particular less than 10°. The bottom is that part of the box on which this is placed and on which it rests on the soil (and is perpendicular to the main growing direction of the plant). The upper side of the box is opposite the bottom and is perpendicular to the main growing direction of the plant. Generally, the upper side is open, but can be covered if desired, for instance with a rigid coverage or with a flexible sheet, e.g. a plastic film.

The box can have any suitable shape. For example it can have a polygonal, e.g. triangular, rectangular, square, pentagonal, hexagonal or octagonal, especially square or rectangular, a circular, oval or irregular bottom shape ("bottom shape" is to be understood as the plan view of the bottom). However, for place-saving reasons and also for production reasons, it has preferably either a square or rectangular and more preferably a rectangular bottom shape.

The box has a height of preferably from 1 to 50 cm, more preferably from 2 to 20 cm, even more preferably from 2 to 10 cm, in particular from 2 to 5 cm and specifically 3 cm to 4 cm.

If the bottom is square-shaped, the edge length is preferably of from 10 to 100 cm, more preferably from 20 to 80 cm and in particular from 30 to 60 cm.

If the bottom is rectangular-shaped, its length is preferably of from 20 to 100 cm, more preferably from 30 to 80 cm and in particular from 50 to 70 cm. Its width is preferably of from 10 to 80 cm, more preferably from 10 to 50 cm and in particular from 20 to 40 cm. Naturally the width corresponds to the shorter edge of the rectangle.

If the bottom has a circular shape, the diameter of the bottom is preferably of from 10 to 80 cm, more preferably from 20 to 60 cm and in particular from 30 to 50 cm.

The thickness of the box walls does of course depend on the size or the internal volume of the box and is typically in the range of from 0.5 to 15 mm, more preferably from 1 to 10 mm, even more preferably from 2 to 8 mm and in particular from 3 to 5 mm (of course except the openings). The bottom part may have a higher thickness, e.g. up to 20 mm or even up to 30 mm or 40 mm.

If the bottom has a polygonal shape, the seedling box has as many side walls as the number of edges forming the polygon. The box has preferably openings on at least 50% of the number of side walls, more preferably on at least 75% of the number of the side walls and in particular on all side walls. Alternatively, the box has preferably openings on at least two side walls, more preferably on at least three side walls and in particular on all side walls. For instance, if the bottom is rectangular or square, the seedling box has preferably openings on at least two side walls, more preferably on at least three side walls and in particular on all four side walls.

If the cross section of the bottom is circular or oval, the openings are preferably distributed in an area corresponding to 20 to 100% of the circumference of the side wall at the respective height and more preferably around the whole circumference of the side wall. The material of the box can be any suitable and commonly used material for this purpose, such as ceramics (e.g. potter's clay), concrete, metal (e.g. aluminium) or preferably suitable plastics, such as polyethylene (PE), especially high density polyethylene (HDPE), polypropylene (PP), including syndiotactic, atactic and isotactic PP, ethylene/propylene copolymers, polyethyleneterephthalate (PET), polyamide, coextrudates of polyethylene or polypropylene with polyamides, coextrudates of polyethylene or polypropylene with ethylene copolymers, such as ethylene vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, coextrudates of polyethylene or polypropylene with polyethylene terephthalate, polyacrylonitrile (PAN), styrene-acrylonitrile, polystyrene (PS) or resinous materials, such as phenol resins, e.g. formaldehyde-phenol resins, polyester resins and the like.

The shape of the openings is not critical and can take any suitable regular or irregular form. Since the openings will generally be produced industrially, they will take a rather regular geometric form, for instance a circular, oval or polygonal, e.g. triangular, rectangular, square, pentagonal, hexagonal, heptagonal or octagonal, form. The dimension of the longest axis in the opening (in case of a circular shape the diameter, in the case of an oval form the major axis, in the case of a triangle the longest edge, in the case of a rectangle or square the diagonal, in the case of higher polygons the longest diagonal) is preferably in the range of from 1 mm to 50 mm, more preferably from 2 mm to 40 mm, even more preferably from 2 mm to 30 mm, particularly from 2 mm to 20 mm, more particularly from 2 mm to 15 mm, specifically from 2 mm to 10 mm and more specifically from 2 to 5 mm.

The number of openings depends on their surface and is preferably chosen so as to permit a sufficient drainage of excessive irrigation water and at the same time not to jeopardize the stability of the box.

The openings may be covered with a grid or mesh in order to avoid the rinsing-out of solid material.

For avoiding or reducing the contamination of the soil beneath the box with agrochemi- cals, the openings are preferably placed above the (imaginary or planned) upper limit of the (highest) medium containing agrochemicals. As already said, this medium can be a separate agrochemical layer, for instance in the form of agrochemicals-containing granules, or the medium can be the growth medium of the plants, specifically soil, containing the agrochemicals. "Highest" means that in case there is more than one layer containing agrochemicals, the openings are positioned above the highest of these lay- ers, i.e. the layer most remote from the bottom of the box, and to be more precise above the highest peak of this highest layer. At least a part of the openings is placed close enough to the upper limit of the (highest) medium containing agrochemicals so as to permit drainage of excessive irrigation water. "Close enough" means at most 3 cm, preferably at most 2 cm above the upper limit of the (highest) medium containing agro- chemicals, e.g. 0 to 3 cm, preferably 0.2 to 2 cm, more preferably 0.5 to 2 cm and in particular 0.5 to 1 cm above the upper limit of the (highest) medium containing agro- chemicals. The openings can be in a certain distance from the upper limit of the (highest) medium containing agrochemicals because the rice plants can also be grown in water.

The upper limit of the highest medium containing agrochemicals or of the growth medium is predetermined by the sort of plant to be grown in the seedling box (different plants have different root forms and require different depths of growth medium) and by the predetermined size up to which the plant is left to grow before transplantation. During the growth of the plants the growth medium may expand due to the growing roots and thus the upper limit may move upward. However this expansion is generally very limited and thus may be ignored.

As seedling boxes are generally filled with the growth medium and the agrochemicals up to a height of from 1 cm to 5 cm, preferably of from 2 to 4 cm, the openings are preferably placed of from 1.5 to 6 cm, more preferably from 2 to 5 cm and in particular from 3 to 4 cm above the bottom of the seedling box.

Agrochemicals can be any sort of chemicals commonly used in agriculture, such as pesticides, e.g. fungicides, insecticides, herbicides, nematicides, bactericides etc., fertilizers, growth regulators and the like. Preferably, they are pesticides and in particular insecticides or fungicides.

"Growth medium" can be soil or an artificial solid growth medium. Preferably it is soil.

In a specific embodiment, the seedling box further comprises openings which can be opened and closed and which are positioned on at least one side wall. The opening and closing is preferably realized by a sliding or flapping mechanism. Preferably these open/close openings are positioned at the level where the growth medium is placed or is to be placed. More preferably, these open/close openings are positioned close to the bottom. These open/close holes are for following process: When the seedling boxes are prepared for planting, they are provided with growing medium, which is then irrigated extensively. The large surplus of water is discharged via these openings be- fore the agrochemicals are applied and the openings are closed and stay closed during the growing of the plants. Moreover, they allow an easy rinsing of the seedling box after transplantation. Closing is effected by any suitable means, e.g. by a board, flap, hatch, sheet, slide, sliding gate, etc.

In a particular embodiment, the invention relates to a seedling box as defined above, containing a growth medium layer, preferably soil, and at least one agrochemical, preferably in the form of a layer comprising granules placed above the growth medium layer.

The invention further relates to the use of the seedling box as defined above for growing plants. Preferably, the box is used for growing young plants until they reach a predetermined size. More preferably, the box is used for growing young rice plants until they reach a predetermined size. The predetermined size is generally the size at which the respective plants are usually transplanted into open land. This depends on several factors, such as plant species and variety, climate of the area where the plant is to be transplanted thereinafter, the size of the box and the density of the plants in the box, etc. and is known to the skilled person.

The invention also relates to a method for growing plants, which method comprises growing the plants in a seedling box as defined above. Preferably, the method serves for growing young rice plants. The method comprises the steps of providing the seedling box with a growth medium and optionally at least one agrochemical, planting the propagation material of the plants to be grown, in particular sowing seeds of the plants to be grown, and growing the plants until they reach a predetermined size. The agro- chemicals) can alternatively or additionally be introduced into the box after sowing.

"Propagation material" embraces seeds, grains, fruit, tubers, rhizomes, spores, cuttings, offshoots, meristem tissues, single and multiple plant cells and any other plant tissue from which a complete plant can be obtained. One particular propagule is seed.

The seedling box of the invention avoids or at least reduces the contamination of the soil on which it is placed with agrochemicals rinsed out with excess irrigation water and reduces the amount of required agrochemicals and water. In the preferred embodiment of the box having no openings in the bottom, the infection of the growth medium inside the box and/or of the seeds or plants with soil-borne diseases originating from the soil on which the box is placed is avoided or at least reduced. Moreover, as in the preferred embodiment there are no openings in the bottom of the box, the plants' roots do not pervade through the openings and thus no root cutting is necessary when the plants are removed from the seedling boxes for example for being transplanted into paddies. This means less labour and also more vigorous plants since cutting the roots is always related with a weakening of the plants.

The invention is further illustrated by the non-limiting figure.

The figure shows schematically a rice seedling box having a rectangular bottom shape (plan view), without openings in the bottom, with openings (1 ) on the side walls closely above the upper limit (2) of an imaginary layer containing granular-type agrochemicals or of an imaginary growth medium layer containing agrochemicals, and open/close openings (3) close to the bottom.

The number and place of the openings (1 ) on the side walls is not to be understood as limited to what is shown in the figure. Instead, the openings can be distributed on all four walls. Neither is the shape of the openings to be understood as limited to the shapes shown in the figure, but might take any suitable form.