Technology of pre-sowing preparation and sorting of vegetable crop seed

The seed of most vegetable crops is small, vulnerable to pathogens, and poorly tolerates spring cold. It is difficult for young seedlings to extract nutrients from the soil before they transition to full photosynthesis. Systematic pre-sowing preparation helps seeds survive the unfavorable period, and low sowing rates for vegetable crops make the costs of such treatment minimal.

Size Sorting and Seed Disinfection

Preparation begins with cleaning and calibrating by size and density. Seed-producing farms use machines like the "Petkus," pneumatic tables, and columns for this purpose. In farm conditions, high-quality dense seeds can be separated using water or harmless salts — common salt or ammonium nitrate.

1. Pour the seed into water or a salt solution and stir.
2. Let it sit for 2–5 minutes.
3. Drain the liquid along with the floating light seed.
4. Rinse the dense seed remaining at the bottom twice thoroughly with clean water and dry it.

After drying, the seed is disinfected. For dry seed treatment, fentiuram and thiogam (3–4 g), apron (4 g), or ridomil (12 g) are used. You can also hold the seed for 20 minutes in a 0.5–1.0% potassium permanganate solution or manganese sulfate, then rinse thoroughly with clean water. The greatest effect is achieved by seed incrustation using stickers, which form a thin water-soluble film and retain pesticides. For this, a 12% solution of sodium carboxymethyl cellulose or a 5% solution of polyvinyl alcohol is used.

Micronutrients, growth regulators, vitamins, and pest repellents can be added to the created protective film. Conventional dry disinfection is carried out in a PS-10 treater, and incrustation is performed in coating machines or small-scale mixers. Thermal treatment is also used to combat viruses and fungal diseases.

Nutrient Enrichment, Pelleting, and Germination

Saturating seed with nutrients increases the emergence energy of seedlings. However, the effect of such treatment decreases if the necessary elements are already present in the soil in sufficient quantity. Agrochemical analysis of the soil allows for the most accurate determination of the additive composition for pre-sowing preparation.

For enrichment, seed is soaked in solutions of salts, acids, and growth stimulants. The composition and concentrations of components for such treatment are selected individually. Basic recipes for working solutions are provided in the table below.

Good results are achieved by using pelleted seed, covered with an organo-mineral mixture. The coating composition includes fertilizers, vitamins, seed treatment agents, growth stimulants, and bacterial preparations. Pelleting allows for precise seed distribution during sowing, saves seed material, and improves seedling nutrition.

Pre-sowing germination activates growth processes even more strongly. The seed is kept in a moist and warm environment until 1–5% of the embryos have sprouted, then dried to a free-flowing state, disinfected, and sown. This technique, like conventional soaking, is mandatory for slow-growing crops — carrot, parsley, and onion. Growth inhibitors that prevent moisture from reaching the embryo are washed out of their coats.

• Concentration of salt solution for calibration — 3–5%
• Disinfection time in potassium permanganate — 20 min
• Warming temperature for cucumber seed — 76 °С
• Proportion of sprouted seed during germination — 1–5%

Bubbling, Warming, and Seed Hardening

Bubbling — holding seed in water saturated with oxygen or air — effectively stimulates germination and increases field emergence. Treatment time ranges from 6 to 48 hours depending on the crop. This technique allows for uniform emergence even in slow-germinating plants.

After bubbling, the seed must be dried at a temperature of 25–30 °C, disinfected, and sown immediately. To optimize the process, pesticides for disinfection can be added directly to the bubbler water during treatment.

To accelerate emergence and increase cold resistance, temperature treatment is used. Dry seed of cucurbits is warmed, while germinating seed of thermophilic and cold-resistant crops is subjected to hardening with low temperatures.

• Dry warming of cucurbits — 50–60 °C (4–5 h)
• Hardening of thermophilic crops — 0 °C (3–5 days)
• Hardening of cold-resistant crops — 0 °C (10–15 days)
• Seed drying temperature — 25–30 °C

In vegetable growing practice, physical methods of stimulation have also been tested: treatment with electric current, ultrasound, laser, magnetic field, and radiation. However, these factors have not shown stable results under production conditions; therefore, using them on farms is not expedient. Such methods are suitable only for experimental work in breeding.

Technological features of vegetative propagation

Vegetative propagation (cloning) is based on growing plants from tubers, bulbs, roots, cuttings, or individual cells. This method allows for the complete preservation of the cultivar traits and properties of the mother plant, which is especially important for heterozygous crops. However, it requires significant labor costs for preparation and planting of material, has a low propagation coefficient, and carries the risk of disease transmission.

Despite the disadvantages, the vegetative method is widely used in vegetable growing in the following cases:

• Loss of ability for seed propagation. Garlic is propagated only by bulb cloves or aerial bulbils; Egyptian onion is propagated by aerial bulbils.
• Prevention of trait segregation. To preserve the cultivar in heterozygous crops, potato is propagated by tubers, rhubarb by division of rhizomes from typical plants, and shallot by bulbs.
• Accelerating harvest. Using parts of adult plants reduces the growing period by one year. For this purpose, the bush is divided (asparagus, tarragon, artichoke, mint), root suckers are separated (artichoke, mint, perennial onions), and stems (tarragon, mint) and roots (horseradish) are used for cuttings.
• Increasing resistance and improving nutrition. To protect against soil pests and diseases, grafting is used: cucumber and melon are grafted onto pumpkin, and tomato onto rootstock tolerant to nematodes.
• Sanitization of planting material. To obtain healthy material for potato and asparagus, plants are grown in laboratories from meristem cells or pollen (tissue culture method).

In addition to the vegetative propagation techniques for vegetable crops listed above, sometimes division of mother plants (beet, onion) into several parts is used to save planting material and increase the propagation coefficient.