Technology of vegetable transplants production by ebb-and-flow method using UGS-4 installations

Seedling production technology using the sub-irrigation method

The production of vegetable seedlings crops using low-volume hydroponic technology in the Russian Federation is based on seedling and lettuce complexes developed by the production and commercial firm LLC "Agrotype". PKF "Agrotype" is also the developer of the technology for seedling production on UGS-4 systems using organic-mineral and inert substrates.

The complex includes:

• hydroponic racking systems (hereinafter referred to as UGS-4);
• a system of main and distribution pipelines;
• intake and storage tanks;
• pumps, filters, plastic channels for installing pots with plants, and other equipment.

The UGS-4 is the main equipment at seedling complexes. It consists of a stationary frame and a movable platform, equipped with a sealed plastic cultivation tray featuring deep longitudinal and shallow transverse grooves, through which the nutrient solution is distributed evenly across the platform area.

The above-mentioned components of the UGS-4 allow for supplying the nutrient solution to the plants (flow-through hydroponics), performing recirculation, and carrying out retention in the cultivation tray (sub-irrigation method).

Seedling production on UGS-4 is quite specific and involves certain limitations in the use of substrates, containers for seedling cultivation, and mineral fertilizers. The requirements for substrates for seedling production using the sub-irrigation method on UGS-4 are the same as those for seedling production using the tray method.

Container selection and equipment preparation

Containers (reusable trays, pots) are selected depending on the type of crop being grown and the time of year, favoring versatility and technological efficiency in production. They must meet hygienic requirements, and their price must correspond to their quality.

Based on many years of experience, LLC Agrofirma "Bedrensky Sad" recommends four standard sizes of reusable trays for seedling production using the sub-irrigation method:

Figure 9 — Trays No. 64 and No. 54

Pot containers are suitable for almost all crops. The most common and versatile are round soft plastic pots with a diameter of 10.5 cm (volume — 0.52 l) and 12.5 cm (volume — 0.8 l). In the spring-summer period, it is recommended to use terracotta and black pots with a diameter of 9 cm (0.3 l), square ones with dimensions of 7 x 7 x 6.2 cm and 7 x 7 x 8 cm, as well as round molded pots with a volume of 0.25 l.

Preparation of the seedling department for sowing includes:

1. Inspection of equipment readiness.
2. Checking the racking units for horizontality (deviations of even 1-2° are unacceptable).

If trays or pots with organic-mineral mixtures are to be used for growing vegetable seedlings, the tables are covered with non-woven materials such as spunbond, agrotest, or noutrosil of medium density, which perform the additional function of filtering the nutrient solution from mechanical substrate particles. If it is not possible to cover all tables with fabric, you can cover only the supply and drainage points of the solution. Figure 10 — Seedlings of tomato in 0.8 l terracotta pots on a UGS-4

When growing vegetable seedlings crops using inert substrates (mineral wool, expanded clay, etc.), the tables do not need to be covered with fabric; the fabric is also unnecessary if good filters are installed to clean the solution from various impurities. Containers for growing various crops are placed on the prepared racking units. Racks with containers are sub-irrigated 2 days before sowing or pricking out.

Seedling cultivation of vegetable crops on inert substrates can be carried out in two ways.

Method 1. Reusable trays are filled with mineral wool plugs ("fingers"), placed on the rack, and saturated with water or nutrient solution one day before sowing. Sowing is performed on the moist "fingers" and lightly covered on top with vermiculite or sifted agroperlite, after which the sowings are covered with film. When 50-60% of seedlings emerge, the film is removed and artificial supplementary lighting lamps are turned on.

Figure 11 — Trays with "fingers"

Method 2. Reusable trays with mineral wool "fingers" are irrigated with a solution and sown, then they are placed on multi-section carts and moved to a seed germination chamber, where a temperature of 24-25 °C and an relative humidity of 80-85% are maintained">relative humidity of 80-85% are maintained. When 90% of seedlings emerge, the trays are placed on the racks and artificial lighting is turned on.

Three days before pricking out the seedlings, mineral wool cubes are laid out on the hydroponic racking units and washed with a standard solution with a pH of 4.8-5.1 and an EC of 1.0 mS/cm; the solution is allowed to drain for 24 hours. Then, they are saturated with the same standard solution with a pH of 5.0-5.2 and an EC of 2.0-2.5 mS/cm. Plugs with seedlings are pricked into the cubes, covering them with vermiculite or sifted agroperlite. The electric lighting regime and microclimate parameters are traditional, in accordance with the recommendations of the originators of the hybrids being grown.

Mineral nutrition of transplants when grown by the ebb-and-flow method is carried out using a nutrient solution, the composition of which is adjusted taking into account the state of the substrate used (pre-fertilized or non-fertilized).

Figure 12 — Arrangement of mineral wool cubes before saturation

Fully soluble fertilizers are used to prepare the solutions. If several vegetable crops are to be grown in the nursery department simultaneously, one nutrient solution can be used for all of them, but the pH and concentration indicators, as well as the volume and number of irrigations, will vary. Recommended nutrient solution composition for all crops (according to O. V. Antipova, 2006): NO3 — 18-22 mmol/l; NH4 — 0.3-1.0 mmol/l; K — 9.0 mmol/l (peat saturation), 6-7 mmol/l (growing); P — 1.8-2.0 mmol/l (peat saturation), 1.25-1.5 mmol/l (growing); Ca — 4.5-4.7 mmol/l; Mg — 1.50-1.95 mmol/l; SO4 — 2.75-3.00 mmol/l; Fe — 30-35 µmol/l (saturation), 20-25 µmol/l (growing); Mn — 10 µmol/l; B — 35 µmol/l; Cu — 0.75-0.90 µmol/l; Mo — 3.5-5.0 µmol/l at pH — 5.6-6.2; EC — 2.0-2.5 mS/cm.

It is advisable to use complex fertilizers for preparing nutrient solutions, as they are highly soluble and contain microelements. This saves time on calculations and separate preparation of microelement solutions, which are mainly produced in sulfate form.

Solutions must be prepared for single use. There is a risk of introducing an infection if the solution is reused, therefore the spent solution must be drained.

Irrigation management for vegetable transplants is based on determining the volume of nutrient solution consumption per rack installation:

V=AxBxC (1), where V — irrigation rate per one rack (cm3);

A — rack width (1825 cm in our case);

B — rack length, cm;

C — depth of irrigation in centimeters.

The volume of nutrient solution consumption per valve is calculated by the formula:

V = A x B x C x d (2), where V — irrigation volume per one valve; d — number of rack installations on one valve.

To achieve optimal moisture before ebb-and-flow irrigation, the pot or tray with substrate should be weighed and their mass recorded. After irrigation for 30 minutes (the first, longest one), the containers or mineral wool cube are weighed again. The mass of pots with organic substrate (depending on volume) before saturation is usually 350-500 g, and after saturation 450-600 g, while the mass of the cube is 500-550 g. The saturated containers and cubes are covered with a translucent film. Sowing or pricking out begins in 1-2 days. After sowing, the substrate surface is lightly sprayed with water and covered with film until seedling emergence. When 80-90% of seedlings have emerged, the film is removed, and irrigation is carried out from above as needed (if the top layer dries out). Upon the appearance of the first true leaf, the pots, trays, and cubes are spaced across the width of the rack. Then a second ebb-and-flow irrigation is carried out, which is shorter than the first one.

In total, several ebb-and-flow irrigations are carried out during the growing season, depending on the state of the crop plants: 1. cucumber — 5-6 irrigations over 22-25 days with an interval of 3 to 6 days; 2. tomato — 6-7 irrigations over 34-36 days with an interval of 3 to 6 days; 3. pepper — 11-12 irrigations over 38-40 days with an interval of 2 to 4 days; 4. eggplant — 10-11 irrigations over 38-40 days with an interval of 3 to 8 days; 5. lettuce — 3-5 irrigations daily for 18-22 days.

Three days before transplanting the seedlings to the permanent growing location, all crops are irrigated with a higher concentration of the nutrient solution.

Disinfection of the nursery line. After completing the crop rotation, it is necessary to disinfect the nursery department, including the entire complex, as a large amount of fungal and bacterial infection accumulates. Pathogenic fungi and others, as well as bacteria of the genera, are most frequently encountered.

All greenhouse structures, hydroponic installations, and the irrigation system must be washed and disinfected. Before proceeding with washing, it is necessary to dry the mobile hydroponic installations, which clearly contain plant residues and substrate suspension after growing plants. It is necessary to sweep all debris with brushes and remove it from the table. Then, drain the residues of working and stock solutions, wash all containers and fill the system with water, fill the tables and clean them with brushes, then drain the water.

Next, the trays are filled with a minimum amount of water, cleaning agents are added, for example, they are left for 5-10 minutes, scrubbed with brushes, and rinsed with water several times.

Then the irrigation system, working and stock tanks are rinsed. A 5% solution of Virkon S preparation is poured into the stock tanks, and the entire irrigation system and the hydroponic unit are disinfected. The solution is kept in the hydroponic unit for 10-15 minutes. Working tools, carts, etc., are treated in the same way.

Disinfection of tools and metal structures

Disinfection of plastic trays is carried out by soaking in a 1% solution of Virocid, followed by mandatory rinsing with warm water 1-2 days after disinfection.

Metal structures and auxiliary equipment are treated with Virkon S at a rate of 300 ml of a 3-5% solution per 1 m2 of the treated surface. After treatment, everything is thoroughly rinsed with water several times. For one of the rinses, a 0.01% KMnO4 solution can be used.

Treatment of irrigation systems and premises disinfection

Disinfection of the nutrient solution supply system is carried out in stages:

1. Introduction of nitric acid and adjusting the pH in the system to 1.5-2.0; exposure time 8-12 hours.
2. Draining the solution and filling the system with a 1% CID 2000 solution, exposure time 8 hours.
3. Draining the solution and flushing the system with clean water until the preparation is completely removed.

To increase the efficiency of the disinfection treatment, room fumigation with hot or cold fog can be performed additionally. The application modes for the preparations are presented in the table: