(A) hole tray seedling production conditions

1. Facilities and equipment

(1) greenhouse Due to the seedling production of light, temperature, water and other environmental requirements are high, it is generally appropriate to use the medium and high-grade glass or double film greenhouse, and requires internal heating, cooling, shade, humidification and other ancillary equipment, as well as mobile seedbeds and so on.

(2) mixing and filling equipment Producers can be based on the scale of production and the main specifications of the seedling tray, and other factors, consider choosing different types of mixing and filling equipment.

(3) seeding machine Mechanized seeding machine is the necessary machinery and equipment for the production of hole tray seedlings. Five common types namely: vacuum template type; compound joint vacuum type; electric eye type; vacuum roller type; vacuum cone type.

Manually operated vacuum template type seeder is the operator will be manually sown to the template with holes, in the vacuum adsorption in each hole adsorption of a seed, the excess seed will be poured out. When all the holes have been sucked up with seed, the vacuum disk is placed on a tube model (or directly on the hole tray). After manually cutting off the source of vacuum air, the seeds drop through the lower seed tube (or directly) into the hole holes, thus completing the sowing of the whole disk at once. Of course, the vacuum template type seeding also has a very high degree of mechanization of the model, which applies to a wide range of seeds, seeding speed is also faster.

Compound joint vacuum type seeder is a compound seeding head will be sucked out of the seed into the lower seed tube. This type of seeding head is usually a row of suction nozzles or suction needles, and the seeds are adsorbed to the suction nozzles by vacuum. Each time the seed is sown down one row, the cavity tray moves forward one grid and then another row is sown. Depending on the size of the seeds, the compound joints of the sowing needles used need to be replaced.

The electric eye seeder (also known as a counting seeder) utilizes electronic eye technology to sort and feed seeds into the hole tray in a counting manner. That is, by the electronic seed counter will identify the seeds, and then these seeds are transferred to a row and the hole of the hole tray corresponding to the arrangement of the lower seed tube, the lower seed tube of the door file in the vacuum operation automatically open, the seeds then fall into the hole. This type of planter can sow seeds of different sizes and shapes without changing the seeding template, compound seeding joints or rollers, but its seeding speed is slow.

Vacuum drum type seeders use a perforated cylinder or drum for seeding. Its working principle is to use vacuum to suck the seed from the seed hopper, and then turn off the vacuum air source, the seed drop into the hole tray. All such seeders have high speed accuracy. However, different drums or cylinders are suitable for sowing different sizes of seeds and hole trays.

Vacuum cone type is operated by utilizing a cone template and a vacuum device. When the cone template is tilted under the action of the vacuum, the seed is naturally poured into the cone. At this point, the burrow tray delivery system located below pushes the burrow tray just below the conical barrel. The cone then opens under vacuum and the seed drops down into the burrow hole.

The above types of seeding machines have their own characteristics, in the choice of type, seedling producers should consider the following aspects, and then make a decision: ① the scale of production and the use of the amount of hole tray. ② Sowing seed type and quantity. ③Technical strength in the hole tray seedling production.

(4) germination room germination room is best to use the insulation of color steel wall and roof, not only easy to keep warm, but also conducive to cleaning, disinfection. Germination room should be equipped with automatic spray humidification device, lighting equipment, air conditioning, mobile germination frame and the corresponding automatic control devices, sterilization devices.

(5) other equipment, mainly perforator, mulching machine, spraying system, seedling transplantation machine, transplantation operating platform, conveyor belt, etc., can be equipped as needed.

2. hole tray nursery substrate and hole tray

(1) substrate for hole tray nursery substrate, requirements: loose structure, light texture, larger particles, lower soluble salt content, pH should be between 5.5 to 6.5. If possible, the substrate should be tested for particle size, cation exchange capacity (EC), overall stomatal volume size and water holding capacity. A good germination substrate should have 50% solids, 25% water and 25% air, and the general density of the dry substrate should be between 0.4 and 0.6 g/cm3. Commonly used substrates include peat, vermiculite, perlite, rockwool, etc., which are mixed according to the seeds, and humidifying agents and nutrient starters are added. Humidifier is used to eliminate the tension knot on the surface of the substrate and improve the waterability to ensure the germination rate of seeds and the neatness of growth.

(2) hole tray The hole tray is mostly made of plastic with square or round holes. Specifications are diverse, commonly used from 6 to 512 holes, and more suitable for woody plant nursery 6 holes, 12 holes, 15 holes, 35 holes, 60 holes, 150 holes, etc., the depth from 40 mm to 200 mm. Generally, the hole tray is required to be thicker and taller for the production of woody seedlings. The length and width of the hole tray is generally 540 mm × 280 mm. In addition, there are thicker, higher type of hole tray dedicated to the cultivation of woody seedlings.

(B) hole tray seedling production and seedling management

1. substrate selection and filling

Selected according to the different seed types and mixed with a good substrate or choose to nursery commercial substrate, and then humidify the substrate with water to the hand after grabbing the ball, but do not squeeze out the water as appropriate. Substrate humidification can make it not easy to leak out of the hole from the hole tray drainage, but not too dry to make the filler after sinking, resulting in a decrease in air permeability. After humidification substrate through the packing machine packing. Filling should be made so that each hole filled with the same amount, and sweep away the residual material, otherwise there will be uneven wet and dry holes in the seedling period.

Filling should leave some space in the holes for sowing and mulching, especially for large seeds.

2. Sowing and covering

Filling the hole tray should be sown in time. Sowing can be based on the seed category to choose the appropriate seeding machine and its internal accessories, such as seeding templates, compound seeding joints or rollers and other ancillary facilities, such as perforators, mulching machines, conveyor systems. Maintain light and ventilation conditions in the sowing environment during sowing, so that the operator can easily check the sowing accuracy. At the same time to maintain low air humidity, so as to avoid small seeds sticking to the machine or sticking to each other.

Most kinds of seeds need to be covered with sowing substrate or other mulch after sowing to meet the environmental conditions needed for seed germination and to ensure their normal sprouting and emergence. Because woody plant seeds are large, adequate moisture needs to be ensured around the seed after sowing in order for it to germinate. And some kinds of seeds can only germinate in dark conditions, in order to meet this characteristic, improve the seed germination rate, to achieve the purpose of shading to promote germination, it is necessary to carry out seed covering. Seed mulching helps to promote the growth of seedling root system. Especially some tree seedling root system is sensitive to light, in light conditions, will make the young roots can not be successfully down into the seedling substrate, thus affecting its later growth.

Mulch should pay attention to the thickness of the mulch, such as covering too little to lose due role; cover too much, the seed will be buried too deep, will make the seed rot increase. Generally speaking, large seeds should be thick mulch. In addition, the mulch should be uniform, such as thick and thin is not equal to make the seedling is not neat, different sizes, not conducive to seedling management, but also affect the quality of the whole batch of seedlings. Covering can be manually operated, but if there are conditions, it is best to use specialized mulching equipment to the hole tray mulching. Now there are more mid-range and high-grade planter have mulching function.

Choosing the right mulching material is also very important, generally the most commonly used mulching materials in addition to seeding substrate, vermiculite, sand and so on. Especially coarse vermiculite, because of its light texture, moisture retention, air permeability is also good, the application is more.

3. Germination room germination

Sowed seeds, watered and placed on the germination frame into the germination room, depending on the type of different, choose to add light or no light, and adjust the appropriate temperature. Different species or varieties of germination time is different. Therefore, when the seed germ root begins to grow out every 1 to 2 days to observe, when there are about 70% of the seedling germ begins to top out of the substrate but the cotyledons have not yet unfolded, it should be removed from the germination room. If it is too late, it may lead to the seedling's futility. In addition, the germination chamber should be cleaned regularly, and if possible, it can be sterilized regularly using ultraviolet lamps or drugs to prevent pests and diseases from occurring in the germination chamber.

4. Management of seedlings

Seedlings removed from the germination room enter the nursery. Because the seedlings just moved out of the germination room are weak and poorly adapted, management should be strengthened and attention should be paid to adjusting the light, humidity, temperature and ventilation.

Temperature: due to the different types of trees, there are often large differences in temperature, the general seed germination and seedling growth in the appropriate temperature of about 18 to 28 ℃. In the appropriate temperature range, the higher the average daily temperature, the faster the growth. The effect of night temperature on seedling growth should not be ignored, especially too low night temperature will inhibit seedling growth. Moderate control of temperature is conducive to robust seedling growth, and too high a temperature is easy to grow.

Humidity: Generally speaking, pre-germination and seedling growth in the early stages of higher humidity is conducive to germination and seedling growth, but the nursery substrate and air humidity is too high is easy to make the plant grow too fast, but also is not conducive to the growth of the root system. At the same time, high humidity is easy to make plants weak and susceptible to pathogen infection. Therefore, moderate humidity control in the nursery can promote rooting and reduce the occurrence of diseases. General air humidity should be about 75% to 85%.

Light: hole tray seedlings, stronger light when seedlings are not easy to grow, short internodes, good branching, strong growth. But if the light is too strong, it will reduce the plant's assimilation and affect growth, and easy to cause leaf burn. And if the light is weak, the seedling grows in vain, the growth is thin and weak, and the tiller is reduced. General hole tray seedlings to 25,000 ~ 35,000 lux is more appropriate, depending on the season, seedling age and tree species.

Fertilizer: hole tray each cell volume is small, the substrate used less, and more for the soilless substrate, fertilizer retention is poor, the external buffer capacity is weak. Therefore, the hole tray seedling fertilization should grasp the "thin fertilizer diligently", "from thin to thick" principle, more liquid fertilizer for foliar spraying. General fertilization can be divided into two stages: one is not applied to seedlings or applied 25 to 50 mg / liter of fully nutritious foliar fertilizer, and the second is the large seedling period to 100 to 200 mg / liter of fully nutritious foliar fertilizer spraying. Throughout the seedling period should be regularly tested plant development, nutritional status, and timely adjustment of the fertilization program. Seedlings can be chased after the appropriate amount of potassium and calcium fertilizer before planting, in order to promote root growth and improve seedling transplantation survival rate.