Container-grown seedlings offer several advantages compared to those grown in beds, making this method more popular.
Advantages of Container-Grown Seedlings
Seedlings grown in containers have a completely uniform vegetative space, allowing for consistent plant growth and high uniformity among the seedlings.
For seedling cultivation, pre-made substrates with good water-air ratios, high water retention, and sufficient nutrient content are typically used, which are adequate for complete seedling development. These substrates are sterilized and free from pathogens, pests, and weed seeds that are often present in soil.
Transplanting can be done with the substrate attached to the roots, which well-developed seedlings fully occupy. Transplanting with a clump of substrate on the roots prevents the stress experienced by plants transplanted with bare roots, allowing them to continue growing steadily. They establish much more easily and quickly, making replanting almost unnecessary. Compared to bare-root seedlings, these container-grown seedlings can be transplanted, if necessary, even into soil that is not optimally moist. This flexibility allows planting throughout the day, optimizing the use of existing planting equipment and facilitating planting over larger areas in optimal time.
Container-grown seedlings mature earlier for harvest and typically yield more than bare-root seedlings grown in beds.
The container method is especially suitable for hybrid vegetable production, where the high cost of seeds makes it crucial to obtain high-quality seedlings from each seed.
Ready-made substrates with good water-air ratios, high water retention, and adequate nutrient content are generally used for sowing in containers, ensuring complete seedling development. These substrates are sterilized and free from pathogens, pests, and weed seeds. Sowing can be done manually or with a precise automated seeder.
Pepper is a plant that is transplanted after developing its first true leaf; therefore, it is sown densely in beds or trays without partitions, or in containers designed for plants that will be transplanted. Such containers are typically 60×40 cm and have 400-450 sowing cells. The seedlings that emerge in these cells are transplanted with the substrate clump, ensuring 100% success and making the process faster and easier compared to transplanting seedlings grown in beds or trays.
Transplanting seedlings from small cells can be mechanized. Transplanting is done when the first true leaf appears. During transplanting, the seedlings are moved from containers with smaller cells to those with larger cells (35 – 50 cm³). Weak or damaged plants are eliminated during transplanting, optimizing the use of space by filling all sowing spots with healthy plants. Transplanted plants are of higher quality and enter the generative phase earlier, producing larger fruits and higher yields. Transplanting can be done manually or mechanically, but in both cases, the substrate must be optimally moistened to avoid damaging the seedlings when pulling them out.
Microclimatic Conditions for Growing Seedlings
To speed up seed germination, containers are placed in germination chambers where the optimal temperature is maintained (at 30°C, almost all seeds germinate within 8 days) with air saturated with moisture using micro-sprinklers that create a mist. Containers remain in these chambers for several days until the seeds germinate. They are then moved to heated protected areas where a consistent optimal temperature is maintained day and night until the seedlings fully emerge, with the substrate kept moist. After the young plants emerge and develop their first cotyledon leaves, the temperature in the protected area should be lowered to 20 – 25°C, with night temperatures being 3 – 4°C lower than daytime, alongside regular ventilation and substrate moistening. This temperature regime is maintained with ventilation for about 40 days, sufficient for developing high-quality seedlings. At this stage, seedlings are 12 – 15 cm tall with 6 – 7 true leaves. In conditions of excessive heat after emergence, seedlings become elongated and weak, leading to poor quality and lower productivity.
Containers in protected areas should be elevated off the ground, achieved by placing bricks or stone blocks on the ground and covering them with a wire mesh or wooden slats. This elevated position allows faster and better warming and prevents root growth through the drainage holes at the bottom of the cells, encouraging the roots to fully occupy the substrate and facilitating easy removal of seedlings during transplanting.
The substrate must be kept moderately moist throughout the seedling growing period. Due to the relatively small volume of the cells, watering should be done in the morning, and moisture should be maintained throughout the day by misting. It is advisable not to mist the plants in the evening or at night. Rainwater collected from the facilities, water from private wells, or clean water from natural sources is best for watering. Direct watering with tap water is not ideal, as it is usually much colder and can negatively affect seedling development. Watering seedlings can be done with automatic overhead sprinklers that create very fine droplets that do not damage young plants or compact the substrate. If watering is done manually, it is essential to use watering cans that create very fine droplets. An automatic watering system can also be used to apply foliar fertilizers like Fertina P, Profert Mara, Kristalon, and others as needed. Foliar feeding is applied when the seedlings lose their dark green color, which often happens when seedlings must remain in containers longer than optimal due to the inability to transplant.
With the use of high-quality treated seeds and growing in sterilized substrates, disease protection for seedlings is generally unnecessary in container cultivation. However, it is advisable to treat seedlings preventively with a contact fungicide based on the active ingredient mancozeb at a concentration of 0.2% or with copper-based fungicides before transplanting.
Several days before the planned transplanting date, protected spaces should be fully opened to allow seedlings direct exposure to sunlight, helping them acclimate to the full spectrum of sunlight they will experience in the field. Before transplanting, the substrate must be moderately moist to facilitate the easy removal of seedlings with the substrate attached to the roots. If the substrate is too wet, it will fall off the roots during planting, while if it is too dry, the plants will not establish well in the field.
