What are the technical key points for raising tomato seedlings in greenhouses in early spring?

In early spring, temperatures tend to fluctuate, and cold air masses often arrive suddenly, which is extremely unfavorable for greenhouse vegetable production. For this reason, vegetable growers are reminded to do a good job of early spring management of greenhouse vegetables, so as to achieve the goal of increasing yield and efficiency. Let's take a look below at a detailed explanation of the technical key points for raising tomato seedlings in greenhouses in early spring.

1. Preparation before sowing

(1) Preparation of nutrient soil

The preparation of nutrient soil must meet 3 conditions: first, use garden soil that has not grown solanaceous crops within 2-3 years and has not been treated with long-acting herbicides; second, the prepared nutrient soil must fully meet the needs of seedling growth; third, it must be loose and well aerated, with strong water- and fertilizer-retention capacity. Usually, use 6 parts high-quality garden soil, 3 parts fully decomposed high-quality farmyard manure, and 1 part finely crushed old slag or plant ash. After even mixing and sieving, mix in 1-2 kg/m3 of superphosphate or diammonium phosphate, 25 g/m3 of 40% quintozene, and 25 g/m3 of 70% zineb, mix thoroughly, and spread evenly in a seedling bed or nutrient tray (60 cm long, 24 cm wide) to a thickness of 8-10 cm. Water thoroughly to settle the soil and prepare for sowing.

(2) Seed soaking, germination promotion, and sowing

First, soak seeds in warm water. Put the seeds in 55 degC warm water and soak for 15 min, stirring while soaking to prevent scalding the seed coat.

Second, chemical treatment. Drain the soaked seeds, then treat them with a 200-fold dilution of 2.5% fludioxonil suspension seed coating agent (Celest) or a 600-fold dilution of 1 million U agricultural streptomycin. This can effectively control damping-off, Rhizoctonia rot, and bacterial diseases during the seedling stage.

Third, germinate at room temperature. Place a previously prepared foam box on a heated brick bed at 28-30 degC, then wrap the treated tomato seeds in gauze and put them in the box. Turn them once every 3-4 h, rinse with clean water once every 8-10 h, and sow once about 80% of the seeds have broken through the seed coat. If sowing cannot be done in time due to special weather, place the seeds in a cool place to slow germination.

Key technical points for tomato seedling raising in greenhouses in early spring

2. Sowing and seedling raising at the right time

Determine the planting time according to the insulation performance of the greenhouse, and then determine the specific seedling raising time according to the planting time and seedling age. The seedling age required for early spring greenhouse tomatoes is generally 80-90 d, and the planting time is generally around April 25. Therefore, the seedling raising time is generally chosen around mid-January.

After sowing, keep the day and night temperatures in the seedling greenhouse at 28-30 degC and 22-25 degC respectively. After emergence, keep the day and night temperatures at 22-25 degC and 17-18 degC respectively. After the seedlings emerge, extend the light duration as much as possible under suitable temperatures. When the light is strong and the temperature is high at noon, shade appropriately to prevent scorching the seedlings. Before emergence, secondary watering is generally not needed. After emergence, if the seedlings are found to be short of water, warm water can be supplied with a sprayer, and large amounts of cold water must not be poured, so as to prevent adverse effects on the seedlings. In early spring greenhouse tomato cultivation, due to relatively large limitations such as temperature and cultivation methods, in order to achieve early marketing and obtain higher returns, growers often raise older seedlings for planting. Standards for strong seedlings: plant height 20-25 cm, stem diameter more than 0.6 cm, with 7-9 spreading dark green true leaves, the angle between the petiole and the stem about 45°, the first inflorescence attached to the 7th-9th node and already beginning to form buds, and the root system required to be intact with no pests or diseases.

Before planting, in addition to fully meeting the water and fertilizer conditions required for growth, the seedlings must also be hardened to adapt. 7-10 d before planting, the transplanting arch shed should be opened early and covered late, and all coverings should be gradually removed. Keep the daytime temperature at 15-25 degC and the nighttime temperature at 10-12 degC to enhance the seedlings' low-temperature resistance and allow them to slowly adapt to the temperature in the planting greenhouse.

3. Transplanting

When the seedlings have 2 leaves and 1 heart, they can be transplanted into 10 cm×10 cm nutrient pots for management. 1-2 d before seedling separation, spray the seedlings with a solution of 1,500-fold Liangdun + 8,000-10,000-fold Bihu mixed with 15 kg of water. On the day of seedling separation, water the nutrient pots thoroughly to settle the soil. After the water infiltrates, spray with 150 mL/hm2 of 30% metalaxylmiddothymexazol aqueous solution + 300 mL/hm2 of 72.2% Previcur aqueous solution mixed with 225 kg/hm2 of water, then place the seedlings in the nutrient pots, 1 plant per pot, and cover with soil 2-3 cm thick.

4. Management after transplanting

In order to promote early growth of new roots, before seedling recovery, focus on increasing temperature, keeping the daytime temperature at 28-30 degC and the nighttime temperature at 20-22 degC.

In order to ensure normal root growth and prevent excessive seedling growth from adversely affecting flower bud differentiation, after seedling recovery, focus on temperature control, water control, and increasing light. Keep the daytime temperature at 20-25 degC, the nighttime temperature at 15-18 degC, and the humidity at 65%-70%. If excessive seedling growth is found, regulate it with a solution of 750 g/hm2 monopotassium phosphate + 120-150 mL/hm2 of 1.8% Atonik mixed with 225 kg/hm2 of water. After seedling recovery, increase the light duration as much as possible. In cloudy and rainy weather, supplemental lighting can be used to provide light, which is beneficial to early flower bud differentiation and promotes later yield formation.

5. Pest and disease control

The main pests and diseases during the tomato seedling stage include damping-off, leaf spot, aphids, and whiteflies. After transplanting and seedling recovery, the following agents can be used: 3,000-5,000-fold 96% Tianda hymexazol, 800-fold 72.2% Previcur aqueous solution, 500-600-fold 72% cymoxanilmiddotmancozeb wettable powder, 3,000-fold 22.4% spirotetramat + 1,000-2,000-fold 3% Tianda acetamiprid, and other agents, sprayed once every 7-10 d to control the occurrence of early pests and diseases.