GB2276525A - Method of and apparatus for preparing pre-germinated seed - Google Patents

Abstract

Seed such as grass seed is pre-germinated in a cylindrical container (12) by soaking in a soak solution under the thermostatic control of an extractor fan (26) mounted in the lid (24) of the container. After draining off the soak solution, the seed is aerated or oxygenated by making air passages through the seed with the aid of spears (54), and then supplying compressed air or oxygen to the drain outlet (18). The pre-germinated seed is passed to a drying installation (100) and tumbles down in a zig-zag path through four drying drums (106, 108, 110, 112). The unit (100) is air-tight and contains an oxygen-free atmosphere of 80% nitrogen with 20% argon. Far-red light at 720 nm is shone into the drums, and the combined effect of the simultaneous dehumidification, light, and oxygen-free atmosphere induces secondary dormancy in the seed so that it can be stored. Storage is in opaque bags (132), also filled with an oxygen-free atmosphere. <IMAGE>

Description

METHOD OF AND APPARATUS FOR PREPARING PRE-GERMINATED SEED Background of the Invention This invention relates to a method of and apparatus for preparing or processing pre-germinated seed, and more particularly a method and apparatus for use with pre-germinated grass seed.

When grass seed is sown in soil in a conventional manner the seeds absorb moisture from the soil or from rainwater or irrigation water. It is well known that the germination period (which is typically between 14 and 21 days when seed is sown conventionally) can be reduced by initially soaking the seed for a limited period before it is sown. When the seed has taken up water in this way it is known as imbibed seed.

It is known to provide so-called pre-germination systems for use with turf grasses. These systems are intended to speed up germination of grass seed and one such system described in European Patent Application EP-A-0 418 741 comprises a drum with a drain valve connected to its base, a vented lid and an aeration insert.

The insert consists of a platform which is supported at a position spaced from the base of the drum, and several upstanding perforated tubes. The insert is designed so that air may flow through the platform, up into the tubes and then radially out of the tubes and through seed located in the drum.

When this system is used the aeration insert is located within the drum and the drum is filled with seed. The seed is then present around but not within the perforated tubes which form part of the aeration insert. The drain valve is of course closed. The drum is filled with water and the seed is soaked for a period of between three and four hours. The drain valve is then opened and the water is drained from the drum. The seed then heats up and air is drawn through the drum via the drain valve and up through the aeration tubes by convention, thereby aerating the seed so that it is left moist but not wet. The seed can then be sown. This system therefore provides a method of treating the seed which comprises soaking, draining and aerating the seed in order to reduce the germination period.

Other systems have been proposed for oxygenation or aeration of seed to assist germination, examples of which are described in European Patent Application EP-A-0 030 575, and French Patent Specifications FR-A-2 462 085 and FR-A-2 599 210. The latter has a drain outlet which can be removed to feed in compressed air. In other proposals a closed or controlled atmosphere has been proposed to assist germination, such as described in United States Patent US-A-4 926 598, which describes the use of an atmosphere enriched with carbon dioxide and ethylene while germinating mung beans, and French Patent Specification FR-A-2 411 567 which describes refrigeration of anemone rhizones in a closed chamber. It has been proposed in European Patent Application EP-A-0 254 569 and United States Patent US-A-4 821 455 to use a rotating horizontal drum in the hydration operation of the germination apparatus.

US-A 4 821 455 proposes also the use of hot air through the drum to dry the seed.

The present inventor has however appreciated that there is a problem with all such pre-germination systems, in that the seed produced has to be used within a relatively short period of time, otherwise it deteriorates rapidly. Typically the seed is only viable for two to five days. This means that the pre-germination equipment must be near to the point of use of the seed, and may need to be constructed so that it is transportable. The seed must be produced as it is required, and cannot be stored for future use.

It is also impracticable to try to sell this seed in small quantities or for the domestic market, as it cannot be delivered and sold sufficiently quickly or consistently.

The present inventor has appreciated that these problems could be overcome if it were possible reliably to render the seed into a dormant state in which it did not deteriorate, and could therefore be stored.

The textbook "Physiology and Biochemistry of Seeds in Relation to Germination", by Bewley, J.D. and Black, M., Volume 2, "Viability, Dormancy, and Environmental Control", pub.

Springer-Verlag, 1982, ISBN 0-387-11656-7, describes the germination of seeds in detail and contains numerous references to prior work. The present specification will assume a knowledge of the contents of this textbook, which is referred to hereinafter as "Bewley and Black".

Bewley and Black discusses inter alia secondary dormancy, which is dormancy induced in a mature, imbibed seed. Many factors are thought to affect secondary dormancy. In particular it is known that nfar-redn light can induce secondary dormancy. Far-red light is understood by those skilled in the art to mean red light in the visible spectrum with a wavelength above about 700 nm, typically extending to 800 nm. Such light induces Dphoto-reversion" and has therefore also been referred to as photo-reverted light. The effect of light at different wavelengths is discussed in Bewley and Black, and reference is made particularly to sections 3.2, 6.3 and 6.8.

Other variables have less clear consequences. These include moisture and water stress, temperature, and the surrounding atmosphere. So far as the latter is concerned, Bewley and Black notes, for example, that dormancy in apple seed can be relieved (ended) by an atmosphere of nitrogen (page 271), but following a discussion of widely differing effects resulting from varied concentrations of oxygen and carbon dioxide (Section 6.7, and Section 6.8 on page 311), concludes that while in some instances secondary dormancy has been reported as taking place under anaerobic conditions, more cases have been reported which suggest that secondary dormancy is usually an aerobic process, because it fails to occur in seeds held in a nitrogen atmosphere; hence the processes are "quite obscure" (Section 6.8.1).

Summary of the Invention The invention in its various aspects is defined in the independent claims appended to this description, to which reference should now be made. Advantageous features of the invention are set forth in the appendant claims.

A preferred embodiment of the invention is described in more detail below with reference to the drawings. Briefly, the preferred system comprises two stages, a first stage in which seed is soaked to initiate germination, and a second stage in which the seed is dried and forced into secondary dormancy in such a way that it can then be stored.

In the first stage of the preferred embodiment grass seed is loaded into an upright cylindrical container and soaked in an aqueous soak solution. Thermostatic control is provided by an extractor fan located in a cover to the container. After draining off the soak solution, the seed is aerated or oxygenated by making air passages vertically through the seed with the aid of pins, and then supplying compressed air or oxygen to the drain outlet so that it passes up through the seed. The seed may then be allowed to stand for some hours with intermittent application of compressed air or oxygen.

This stage initiates the metabolic germination process to a point just prior to radicle emergence; we refer to seed in this condition as pre-germinated seed.

When this first stage is completed, the pre-germinated imbibed seed is passed to a drying installation, and tumbles down through four drying drums. The drying installation is air-tight and contains an oxygen-free atmosphere of 80% nitrogen and 20% argon. Far-red light at 720 nm is shone into the drums, and the combined effect of the simultaneous dehumidification, light, and oxygen-free atmosphere induces secondary dormancy in the seed in a way that it can be stored for relatively long periods.

Storage is in opaque bags which are also filled with an oxygen-free atmosphere.

Brief DescriPtion of the Drawings The preferred embodiment of the invention will be described in more detail, by way of example, with reference to the drawings in which: Figure 1 is an exploded view of a soaking apparatus for pre-germination seed; Figure 2 is a similar view of a modification of the soaking apparatus of Figure 1; Figure 3 is a side sectional view through a drying installation for receiving the pre-germinated seed; Figure 4 is an end view of the installation of Figure 3 taken from the right side in Figure 3 with the end cover 164 removed; Figure 5 is an end view of the installation of Figure 3 taken from the left side in Figure 3 with the end cover 166 removed; and Figure 6 is a view taken on the line VI-VI in Figure 3 showing the interior of the drying drums.

Detailed DescriPtion of a Preferred Embodiment of the Invention The example illustrated in the drawings involves preparing the seed in two stages. The first stage is the soaking and pre-germination stage, where imbibed seed is produced and allowed to commence the metabolic germination process. When germination has started, and at a point prior to radicle emergence, the seed is then transferred to a drying stage. Two alternative forms of soaking apparatus are shown in Figures 1 and 2 of the drawings. The preferred drying apparatus is illustrated in Figures 3 and 6.

I. Soaking Stage The soaking apparatus 10 shown in Figure 1 of the drawings is used in the initial stages of the treatment of grass seed in order to reduce the germination period thereof and comprises an open-top drum-like container 12 having a base 14 which defines an aperture 16 where a manually operable valve 18 is designed to be connected to the base. The drum has a first lid 20 with apertures 22 for ventilating purposes. The drum also has a second lid 24 which is of a domed construction and which includes a thermostatically-controlled extractor fan 26. The thermostatic sensor may be half way down on the inside of the container 12.

Both of the lids 20, 24 are, of course, designed to be mounted upon the upper edges of the wall of the drum in order to extend across the open top thereof.

A mesh platform 28 is supported upon the upper edge of a cylinder 30 which is designed to be slidingly received within the drum-like container 12 so that the mesh 28 is supported horizontally at a position above the level of the base 14.

An oxygenation insert 32 is composed of a domed lid 34 with a hose or the like 36 extending away from the centre of the top of the lid for connection to a source of compressed air. The underside of the dome is closed off by a plate which-carries a plurality of hollow depending fingers 38. Each finger 38 is open at its top end where it is connected to the plate which extends across the lower part of the domed lid. At its free end each finger is closed. Over its length each finger 38 defines a plurality of small apertures 40, such that compressed air supplied through the hose 36 may pass into the domed lid 34 and then into each of the fingers 38 and radially outwardly through the apertures 40.

When using the apparatus of Figure 1 in order to treat grass seed, the valve 18 is initially connected to the aperture 16 in the base 14 of the container 12 and is set to the closed position. The mesh platform 28 is inserted into the container and the container is then filled with seed to a level 15 cm from the top of the container. An appropriate batch card is made out in order to keep a record of the treatment of the seed with the card containing details of the particular type of seed being treated. The container is then filled with a soak solution at a temperature of approximately 24 C. The temperature of the soak solution may vary within the range 20"C to 25cm.

The soak solution is an aqueous solution containing 0.58 of 66.5% W/W propamocarb hydrochloride, 1% of 0.0005% cobalt chloride and 1% of 0.0005% sodium molybdate. When the container has been filled with soak solution the lid 20 is positioned on the open top of the container and the soak commencement time is marked on the batch card.

The seed is left to stand in the soak solution for approximately three and a quarter hours. After the required period of soaking the soak solution is released from the container 12 by opening the valve 18. Once the soak solution has been drained from the container the lid 20 is removed and, with the valve 18 left in the open position, the seed is oxygenated. This is effected by inserting the oxygenation insert 32 into the seed via the open top of the container so that the fingers 38 are pushed into the seed and the domed lid 34 is positioned adjacent the top of the container.

Compressed air is then supplied to the oxygenation insert as indicated by the arrow 42. The air is, of course, forced to pass through the seed. Typically the duration of oxygenation is approximately ten seconds although this may, of course, vary according to the particular specie of grass seed which is being treated.

When oxygenation has been completed the oxygenation insert is removed and the second lid 24 is positioned on the open top of the container 12. The thermostat which serves to activate the extractor fan 26 is set to the required temperature and the unit is switched on. The seed is then left to stand until a period of twelve hours has elapsed from the soak commencement time. During this standing period the seed will heat up and, by convection, warm air rises, causing more air to be drawn into the container via the open valve 18. The temperature-controlled extractor fan 26 maintains the temperature in the container within the range 20"C to 24 cm, being switched on and off appropriately by the setting of the thermostat. It will be appreciated that pre-germination therefore takes place under controlled environmental conditions.

When twelve hours have elapsed from the soak commencement time the seed is rinsed by closing the valve 18, removing the lid 24 and filling the container with water at a temperature of approximately 24"C so that the seed is covered. The valve 18 is then opened again in order to drain the water from the container.

The seed is then oxygenated again by introducing the oxygenation insert 32 into the container and supplying compressed air for a period of approximately ten seconds in the same manner as described above. Once the second period of oxygenation has been completed the oxygenation insert 32 is removed and the lid 24 is replaced on the top of the container with the thermostat again being set in order to maintain a temperature within the range 20"C ro 24"C in the container.

The seed is now left to stand for a period of time which is dependent upon the particular specie of grass seed being treated and the intended final use of the seed. However, the period for which the seed is allowed to stand will typically be within the range 24 to 48 hours although it could be longer. Thus, for perennial ryegrass (lolium perenne) the period is approximately 24 hours, for fescues (festuca rubra, festuca commutata and festuca longifolia) the period is approximately 36 to 48 hours, whilst for kentucky bluegrass (poa partensis) the period is within the range of 72 to 96 hours. During this standing period the seed is examined microscopically from time to time and the period for which the seed is allowed to stand will depend upon the results of these periodic examinations. Examination will involve studying the seed under microscope to assess when the desired stage of pre-germination has been reached. This will generally be just prior to radicle emergence. When this point is reached the seed is removed from the container 12 and is transferred into a drying machine such as is shown in Figures 3 to 6 of the drawings.

The size of the container 12 may vary and it is envisaged that containers having a capacity of 60 - 70 litres, 250 litres or 800 litres, can be provided. The largest container may be designed to have two valves 18 fitted to its base.

Figure 2 is a similar view of a modified soaking apparatus 50 based on that of Figure 1, and in which corresponding parts are given the same reference numbers.

The apparatus 50 differs from the apparatus 10 of Figure 1 in that the drain valve 18 is located at the bottom part of the side of the container, and more particularly in that the oxygenation insert 32 is not used. Instead a disc 52 carries depending parallel spears 54 such that, after steeping the seed in water and then draining the water off, the pins or spears can be lowered into the wet seed in the container. The spears reach substantially to the level of the mesh platform 28. The disc 52 and spears 54 are then removed, leaving vertically-extending air passages formed in the seed.

Air or oxygen is then introduced through the drain valve 18 into the bottom of the container. The air passes up through the mesh platform 28 and into the seed. The air passages made by the spears allow the air or oxygen to pass up through the seed, which would otherwise form too solid a block for the air or oxygen to effectively penetrate through the seed. By using the valve 18 bidirectionally, so as to drain water out and also admit air or oxygen, the structure is simplified.

Preferably the spears 54 take the form of hollow tubes with an inlet at the top and an outlet at the very bottom. When the spears are fully inserted in the drum with the lowermost ends of the spears on or just above the mesh 28, a blast of air or oxygen is forced down the spears. This clears away the seed at the bottom of the spears allowing air to move from below the mesh 28 into the passages formed by the spears more easily.

As with the apparatus of Figure 1, the seed is placed in the container 12 and allowed to soak. The water is drained off, and compressed air (or oxygen) blown in through the valve 18.

Preferably an oxygen-enriched air mixture could be used. The air is blown in intermittently, for a few seconds every hour or so.

Germination then takes place encouraged by the oxygen in the air.

This typically takes 24 to 36 hours.

From the time when the seed is put into the soaking drum 12, it is denied exposure to red light in the wavelength range 520 nm to 700 nm. This is assisted by making the drum 12 and covers blue in colour, and by transporting the seed to the drying stage in darkness. This may be done using opaque bags, or in a larger installation by use of an enclosed conveyor.

II. Drvincr Staae The point at which the seed needs to be removed from the container 12 and transferred to the drying stage depends on the type of seed, and is best found by simple experiment. In general, it is likely to be the point at which no change to the seed is apparent to the naked eye, but where the commencement of germination is apparent under a microscope; that is to say just prior to emergence of the radicle.

The seed is then transferred to the drying apparatus 100 shown in Figures 3 to 6. The apparatus 100 comprises a frame 102 supporting a generally rectangular housing 104 containing four cylindrical drying cylinders or drums, 106, 108, 110, 112. The housing may be about 2 to 2.5 metres high, and the drums about 1.5 to 2 metres long and about 0.4 m in diameter. The housing 104 forms an air-tight surround. An input hopper 114 is mounted on the top of the housing 104 with a valve 116, driven by a motor 118 and a drive belt 120, regulating the flow of seed out of the bottom of the hopper. The valve 116 comprises four chambers formed as quadrants about an axle, rotation of which causes seed to flow through the valve while restricting the flow of air out through the valve.

Such valves are of known type.

From the valve 116, the seed falls into a fixed chute 122 which leads into the open end of the first drum 106. The drums are mounted, as described below, so as to be at a slight slope to the horizontal, and are rotated. Thus the seed gradually tumbles from one end of the drum to the other. When it reaches the further end of the drum, it falls from the drum 106 through a chute 124 into the second drum 108. It traverses the length of the second drum and is directed by a similar chute 126 into the third drum 110. From the distant end of the third drum it passes through a chute 128 to the final drum 112, and from here to an outlet hopper 130. The seed thus follows a zig-zag path down through the drums, each of which is lower than the preceding one. The seed collects in the hopper 130, which is sealed at the bottom by a sliding plate (not shown), until the hopper is sufficiently full, when the sliding plate is opened and the seed falls into a black plastic sack 132.

The construction of the drums will now be described. As shown in Figure 6, each drum has a number of internal paddles or vanes 134 extending along its length, so that as the drum rotates the seed falls over the vanes in a waterfall effect and is fully exposed to the surrounding drying atmosphere. There are three vanes 134 on each of the drums 108, 110 and 112, and a larger number, shown as five, on the first drum 106. Each drum is mounted on an exle 136 by means of an X-shaped cross-piece 138 at each end of the drum, and the axle 136 extends between two end plates 140 which are closely spaced from the associated ends of the housing 104.

Reverting to Figure 3, one end of each axle 136 is journalled in the end plate 140 and carries one or two pulleys 142.

The pulleys are linked by drive belts 144 (Figures 3 and 4) such that drive from the lowest drum 112 is transferred upwardly by the belts 144 to each of the other three drums in turn. The first drum is driven by an electric motor 146, mounted on one side of the housing 104, by a gearbox 148 and a further belt 150.

As shown in Figures 3 and 5, the other end of each axle 136 is not journalled in the end plate 140 but rather passes through a vertical slot or large hole in the end plate and is received in a bush formed in the lower end of a strut 152. This end of each of the four drums is mounted in an adjustable manner so that the slope of the drums can be varied. As the slope is altered there is a slight longitudinal displacement of the end of the axle, consequent upon the end of the drum swinging in a small arc, which displacement is taken up by movement of the strut 152. Each strut 152 is coupled to an adjustment linkage which includes a horizontal arm 154, to the centre of which the upper end of the strut 152 is connected. The horizontal arm has one end pivoted on the outer side of the end plate 140, and its other end pivoted to a vertical strut 156, the further end of which is pivoted on a block 158 which is threaded onto a long vertical screwthreaded rod 160. As shown in Figure 5 the drums are coupled in pairs to two rods 160, because as that end of the first and third drums 106, 110 goes up, the same end of the second and fourth drums 108, 112 should go down, and vice versa. The threaded rods 160 are extended downwardly below the housing 104 so that they can be turned by an operator to adjust the drum tilt. Rotation of the rods 160 causes the blocks 158 to travel vertically on the rods, thus adjusting the vertical height of the end of the associated drum through the strut 156, arm 154 and strut 152. Adjustment of the tilt varies the speed at which seed passes through the apparatus.

Each of the end plates 140 carries a number of holes 162.

Several holes are arranged within the circumference of the associated drum about the position of the axle 136. Over the end plates and forming part of the housing 104 are end covers 164, 166, which serve to seal the housing 104. In this way two chambers 168 are formed, one at each end of the housing.

A conventional dehumidifier unit 170 is located within the base 102. The unit 170 is provided with four flexible ducts. Two of these ducts 172 connect the output of the dehumidifier to the chamber 168 at one end of the housing and the other two of these ducts 174 connect the inlet of the dehumidifier to the chamber 168 at the other end of the housing. The dehumidifier unit 170 includes a drier and a fan, and causes dry air to flow outwardly through the ducts 172 into the chamber 168 between the end cover 164 and the adjacent end plate 140. Thence the air flows through the holes 162 into the drums and passes along the length of the drums, out through the holes 162 at the other end, and into the chamber 168 between the end cover 166 and the other end plate 140. The ducts 174 then convey the air back to the dehumidifier 170.

The ducts 172 are spaced sufficiently widely, as shown in Figure 4, for the operator to get between them to remove the sack 132.

Also in the space between the end plates 140 and the end covers 164, 166 are lights 180. The lights are preferably mounted on the end plates 140 but may be mounted on the end covers, as shown, in either event such that light passes through the holes 162 into the drums. The lights provide far-red light in the wavelength 700 nm to 800 nm and do not provide any substantial light in the range 520 nm to 700 nm. The preferred wavelength is centred on about 720 nm, but it may vary with the specie of seed being treated.

In operation, the drying apparatus is first sterilized to remove any traces from previous use. Then the gas circuit comprising the housing 104, ducts 172, 174 and dehumidifier 170'are filled with an anaerobic gas or gas mixture. A suitable mixture comprises 80% nitrogen and 20% argon though a suitable range for the argon content might be 10% to 40%. Nitrogen alone is lighter than air and tends to float away, so argon, which is heavier, is included. Other gases, such as carbon dioxide or a mixture of gasses, could be used. In any event the oxygen content is substantially eliminated.

The lights 180 are illuminated and pre-germinated imbibed seed from the apparatus of Figure 1 or Figure 2 is introduced into the hopper, the electric motors are started, and a steady flow of seed is passed through the drums as they are rotated. The tumbling action causes the seed to be well exposed to the dry gas flow, and the seed gradually dries as it passes through the drying apparatus.

As the seed passes through the drums, it is simultaneously subjected to three influences: (i) drying due to the action of the dehumidifier, which may include a heater or temperature control; (ii) irradiation with far-red light, which passes into the drums through the ends; and (iii) exposure to an oxygen-free atmosphere.

We have found that the immediate simultaneous application of these three factors can be sufficient to render the seed dormant in a way which will allow it to be stored for a substantial period of time, say up to one year.

To hold it in this condition, the seed is removed in sealed bags which are opaque so as not to let in light and which do not contain oxygen. The bags 132 are collapsed when placed below the outlet hopper 130, and not only fill with seed from the hopper but also receive the same gas atmosphere as exists in the hopper. The bags are sealed closed in this position. Thus the seed is stored in an oxygen free or at least substantially reduced atmosphere in the bags. The nitrogen and argon used in this example are conveniently introduced into the apparatus at the outlet hopper 130.

The bags used may be black polyethylene bags of 1000 gram/sq. metre weight and may be sealed by heat sealing.

Alternatively the bagging-off chamber below hopper 130 could be split into two sections, with nitrogen and argon being introduced into the bottom of the chamber to be filled. When one section of the bagging-off chamber is full, the seed flow is diverted to the other unfilled part. Nitrogen is pumped under pressure into the chamber until there is only 1 to 5% oxygen. The seed is then released into the bags.

The bags may contain 10 kg of seed in an atmosphere of less than 5% oxygen, at atmospheric pressure.

The degree of drying may depend on the specie of seed but will typically lead to a moisture content in the range 10 to 15%.

The seed is sampled in the drums and the rate of drying adjusted accordingly.

The seed is exposed to far-red light for a period of time which typically varies between 10 mintues and 1 hour, depending again on the specie of seed and the inherent seed coat thickness.

While the seed is in the final drum, nutrients, fungicide or other products can be applied by means of an atomizer or a powder applicator.

The seed prepared using the apparatus illustrated has storage properties which are vastly superior to presently-available pre-germinated seed. Hitherto it has not been possible to produce seed that can be stored in the packed condition without rapid deterioration. It is believed that the effectiveness of the present method resides in the prompt and simultaneous application of the exposure to far-red light and elimination of normal red-light on the one hand, and the oxygen-free or inert atmosphere on the other as soon as the drying operation starts. These dormancy-inducing influences operate as the drying takes place to set the seed into secondary dormancy as it dries.

It is likely that seed prepared by this method will be superior to presently-available pre-germinated seed in the speed at which it grows once it is sown, and is subjected again to moisture, white light, and oxygen. Speed of growth when plant

Many modifications may be made to the apparatus described and in particular it may prove that all three influences of drying, irradiation and oxygen reduced or free atmosphere are not necessary for certain types of seed. It is also known that while far-red light is the most effective at reducing secondary dormancy, blue light of wavelengths below about 520 nm can also produce the same effect, even though longer exposure may be necessary, see Bewley and Black, Section 3.2.1. However, light in the range 520 nm to 700 nm is excluded. To reduce the danger of stray light inhibiting the intended effect of the light, the interior of the drying installation is preferably painted blue.

While described in relation to grass seed, the method described may also be used to initiate the metabolic germination process with other seed, particularly with cereals, though it may be usable with a wide variety of seed such as turnips or parsnips, for example. The precise optimum operational parameters for different seeds can only be found empirically.

Claims (31)

1. A method of preparing pre-germinated seed, comprising the steps of: (a) receiving imbibed seed; (b) drying the seed; (c) exposing the seed to light of a wavelength that tends to induce secondary dormancy; and (d) exposing the seed to an oxygen-free or substantially oxygen-reduced atmosphere; the steps (b), (c) and (d) being conducted simultaneously.

2. A method according to claim 1, in which the light to which the seed is exposed has a substantially zero component in the wavelengths 520 nm to 700 nm.

3. A method according to claim 1, in which the light to which the seed is exposed consists of light with wavelength greater than 700 nm.

4. A method according to claim 1, 2 or 3, in which the step of exposing the seed to an oxygen-reduced atmosphere comprises exposing the seed to an atmosphere containing less than 5% oxygen.

5. A method according to claim 4, in which the seed is exposed to an atmosphere comprising nitrogen, argon or carbon dioxide, or a mixture thereof.

6. A method according to claim 5, in which the seed is exposed to an atmosphere comprising 10% to 40% argon, with the balance being nitrogen.

7. A method according to any preceding claim, in which the seed is dried to a moisture content of from 10% to 15%.

8. A method according to any preceding claim, in which after completion of the steps (b), (c) and (d) the seed is packed in sealed, opaque containers under an oxygen-free or substantially oxygen-reduced atmosphere.

9. A method according to claim 8, in which the atmosphere in the bags is the same as the atmosphere in step (d).

10. A method according to any preceding claim, in which during step (b), nutrients and/or fungicides are added to the seed and the seed is agitated.

11. A method according to any preceding claim, in which the seed is grass seed.

12. A method according to any of claims 1 to 10, in which the seed is cereal seed.

13. A method of preparing pre-germinated seed, comprising the steps of: (a) receiving pre-soaked seed; (b) subjecting the seed to a drying gas flow; and (c) exposing the seed to light not substantially including wavelengths in the range 520 nm to 700 nm; the steps (b) and (c) taking place at the same time.

14. A method of preparing pre-germinated seed, comprising the steps of: (a) receiving pre-soaked seed; and (b) subjecting the seed to a drying gas flow; the drying gas flow comprising an oxygen-free or substantially oxygen-reduced gas composition.

15. A method according to claim 14, further including the step of packing the resultant seed into opaque containers, the containers containing an atmosphere comprising an oxygen-free or substantially oxygen-reduced gas composition.

16. Apparatus for preparing pre-germinated seed, comprising: a substantially sealed housing; at least one rotatable drum inclined to the horizontal, open at both ends, and containing structures extending along the interior thereof to assist aeration of seed in the drum; means for passing a drying gas flow through the housing, such as to pass along the interior of the drum; means for receiving seed input to the apparatus and causing it to enter the upper end of the drum; means for extracting seed from the apparatus after it has passed along the inclined drum; and means for illuminating the seed within the housing with light having substantially zero component in the wavelengths 520 nm to 700 nm.

17. Apparatus according to claim 16, in which there are a plurality of drums and the seed passes sequentially through the drums.

18. Apparatus according to claim 17, in which each successive drum is lower than the preceding drum and the seed follows a zig-zag path through the drums.

19. Apparatus according to claim 16, 17 or 18, in which the said structures in the drum comprise paddles or vanes extending inwardly from the periphery of the drum.

20. Apparatus according to any of claims 16 to 19, in which the inclination of the drum is adjustable.

21. Apparatus according to any of claims 16 to 20, in which the means for extracting seed comprises an outlet over which a bag can be sealingly affixed to receive seed without substantial ingress of external air.

22. Apparatus according to any of claims 16 to 21, in which the illuninating means comprises light sources which illuminate the seed when in the drum.

23. Apparatus according to claim 22, in which the light sources shine into at least one end of the drum.

24. Apparatus for drying seed, comprising: a substantially sealed housing; a plurality of rotatable drums inclined to the horizontal and arranged with each successive drum lower than the preceding drum and inclined in the opposite direction; means for receiving seed input to the apparatus and causing it to end the upper end of the first drum; means at the ends of the drums for passing seed from the lower end of one drum into the upper end of the next drum, such that the seed follows a zig-zag path through the drums; means for extracting seed from the apparatus after it has passed through the last drum; structures extending along the interior of each of the drums to assist aeration of seed in the drum; and means for passing a drying gas flow through the housing such as to pass along the interior of the drums.

25. Seed, particularly pre-germinated seed, packed into opaque bags with an atmosphere in the bag containing less than 5% oxygen.

26. Apparatus for pre-germinating seed, comprising: a container within which the seed can be soaked in a soak solution; a cover for the top of the container, the cover incorporating a thermostatically-controlled extractor fan to maintain the atmosphere in the container within a predetermined temperature range; means at the lower portion of the container for draining the soak solution and for the ingress of air or oxygen.

27. Apparatus for pre-germinating seed, comprising: a container within which the seed can be soaked in a soak solution; means at the lower portion of the container for draining the soak solution and for the ingress of air or oxygen; and spear means which can be forced downwardly from the top of the container to form a plurality of air or oxygen channels upwardly through the seed.

28. Apparatus according to claim 26 or 27, in which the means for draining the soak solution and for the ingress of air or oxygen comprises a single closable aperture to which a source of air or oxygen can be connected.

29. A method of preparing pre-germinated seed, substantially as herein described with reference to Figures 3 to 6 of the drawings.

30. Apparatus for pre-germinating seed, substantially as herein described with reference to and as shown in Figure 1 or Figure 2 of the drawings.

31. Apparatus for preparing pre-germinated seed, substantially as herein described with reference to and as shown in Figures 3 to 6 of the drawings.