Significance and advantages of the transplant method in modern vegetable growing

The use of the transplant method is one of the main features of vegetable growing. It makes it possible to intensively use arable land and natural environmental factors that determine the growth and development of plants. Its essence lies in the fact that young plants are first grown in favorable conditions (naturally occurring or artificially created), and then they are transplanted into open or protected soil to obtain a harvest. Young plants themselves, which have not yet begun to form productive organs and are grown for the purpose of subsequent transplanting, are called transplants (seedlings).

Unlike the transplant method, growing plants by means of sowing seeds directly into open soil is called direct seeding or direct-seeded culture.

The transplant method has many advantages, which is why it is widespread in all countries of the world engaged in vegetable production. In climatic zones where there are significant seasonal changes in temperature conditions, the transplant method allows for fuller use of natural light in early spring, when the thermal regime does not yet allow for growing main vegetable crops in open soil. Using the transplant method, it is possible to obtain an early harvest in open soil due to the "head start" in the growth and development of plants transplanted from protected soil structures, i.e., to artificially extend the growing season of vegetable crops. It is the transplant method that has allowed thermophilic crops to be moved far to the north, where the duration of the warm period is too short for many valuable vegetable crops. In the south, it is possible to more rationally use arable land when growing plants from transplants. While thermophilic plant transplants are being grown in protected soil, one can obtain a harvest of early-ripening cold-resistant crops (radish, garden cress, leaf mustard, etc.) on the plot where they will be planted. This example convinces us that the transplant method allows for two to three harvests per year from a single field and proves the great economic significance of this method. Reducing seed consumption by three to four times compared to the direct-seeded culture of vegetable plants is of equal importance. Moreover, dense seedling cultivation requires fewer expenses for their protection against unfavorable conditions, diseases, and pests, which also provides an economic effect. And finally, one should note the significant importance of the transplant method in solving the problem of year-round vegetable production and consumption.

The disadvantages of the transplant method are mainly associated with high costs, including capital expenditures, for the creation and operation of special structures for growing transplants, as well as with increased expenses for their transportation and planting compared to sowing seeds. Creating favorable conditions for the growth and development of transplants at the end of winter and the beginning of spring requires meticulous work by well-trained specialists. But despite such serious drawbacks, the transplant method is widely used in growing almost half of the main vegetable crops.

However, it is not advisable to grow all vegetable crops using this method. It is applicable only for plants that relatively quickly restore lost roots and therefore easily tolerate transplanting.

Sometimes the transplant method of cultivation is used for plants that poorly restore roots when transplanted (cucumber, melon, watermelon, pumpkin), but this is possible only with the use of special containers, trays, or pots that allow for almost complete preservation of the young transplant's roots. The latter ensures relatively fast establishment of the transplanted plants of these crops.

Some crops cannot be grown through transplants due to a decline in marketable yield quality. This applies to carrots, parsley, and chicory, which exhibit root branching after being transplanted. It is economically disadvantageous to use the transplant method for crops with a small rosette, where more than 300 thousand plants are placed per hectare (leaf lettuce, spinach, dill, radish).

Early vegetables are grown mainly using the transplant method, whereas when obtaining a late harvest for processing and placing into storage, it is more economical to use direct-seeded culture.

The timing for growing transplants for open soil depends on the heat requirements of the crops, the time of their planting, the planned harvest dates, the type of transplant structure, and several other factors. In the south of our country, transplants of various vegetable crops begin to be planted from the first ten days of March (under plastic covers) and finish in June-July, which in total duration accounts for more than three to four months. In more northern regions, this period is significantly shorter, but it is sufficient.

Therefore, Academician G. I. Tarakanov classifies transplants being grown as early, mid-season, and late. This classification is based on the timing of growing and planting, and to some extent, the age of the transplants when planting into the soil. However, depending on the agro-meteorological zone transplants of the same crops may be assigned to different groups based on their growing periods. For example, pepper and eggplant transplants in the North Caucasus are considered mid-season, while in the non-chernozem zone, they are considered early. This once again confirms that the division of transplants into early, mid-season, and late is determined not by the crop itself, but by the timing of its cultivation and planting into the soil.

The transplant method allows for a head start in plant development, accelerates the ripening of vegetables, and increases overall yield. However, the economic efficiency of the technology depends on the precise adherence to the age of transplants and the timing of their planting. If you overgrow the seedlings in the greenhouse or plant them underdeveloped, the plants will take a long time to establish and may shed their first fruit set.

To plan a planting conveyor, transplants are divided into three main groups. The planting dates and optimal seedling age for each are shown in the table below. These guidelines help to calculate the exact dates for sowing seeds.

For southern regions, the distribution of crops by groups has its own specifics. It is important for an agronomist to consider the temperature requirements of each species when choosing a planting method:

• Early transplants: planted in open soil (early white cabbage and cauliflower, onion, celery) or under plastic film (tomato, cucumber, pepper, eggplant).
• Mid-season transplants: tomato, cucumber, pepper, eggplant, mid-season cabbage.
• Late transplants: late white cabbage and cauliflower, broccoli, and other crops for a late autumn harvest.

Structures for growing transplants

Each group of transplants requires specific conditions for protection against frost and heat maintenance. The type of structure is chosen based on the sowing dates and the climatic features of the zone. The design of greenhouses or hotbeds must ensure an optimal microclimate during all stages of the growing season.

• Early transplants are grown in heated plastic greenhouses or hotbeds. It is necessary to maintain a favorable temperature regime in them from the end of January to the end of March.
• For mid-season transplants in the southern zone, special solar-heated plastic greenhouses, cold hotbeds, or primitive plastic covers are used.
• It is advisable to grow late transplants in open nurseries with prepared soil beds or on soil enriched with mineral and organic fertilizers.

• Heating period for early transplants — from late January to late March
• Direct sunlight on plants — several hours a day