Technology of greenhouse soil preparation for growing vegetable transplants

Preparation of greenhouse soil directly determines seedling quality and the timing of its readiness for planting. The choice of tillage technology depends on greenhouse heating, the number of crop rotations, and exactly how you grow the seedlings — in pots or without them. The right approach allows for a significant reduction in fertilizer and labor costs.

Soil tillage technology for different types of seedlings

When growing potted seedlings, the soil is prepared in autumn according to the requirements of the subsequent vegetable crop. Appropriate application rates of fertilizer are applied and the soil is tilled to a depth of 20–25 cm. The main thing here is to perfectly level the surface for the pots, for which it is better to use electric tillers followed by manual leveling.

For bare-root seedlings, the tillage depth is different. Organic fertilizers for tomatoes and mid-season cabbage are applied in autumn and incorporated with a tiller to a depth of up to 10 cm. Increasing this nutrient layer to 20 cm makes no sense: 80% of bare-root seedling roots are concentrated in the top 10 cm. Deeper tillage will only double fertilizer consumption and lead to severe root breakage when harvesting seedlings.

• Tillage depth for pots — 20–25 cm
• Incorporation depth for bare-root seedlings — up to 10 cm
• Share of roots in the topsoil layer — 80%
• Bed width for autumn furrowing — 1.6–1.8 m
• Application of mineral fertilizers — 3–4 days before sowing

The timing and specifics of soil preparation also depend on the intensity of greenhouse use. Greenhouses with air heating are used in two rotations from March to September. After harvesting mass-season tomato seedlings and mid-season cabbage, peppers or melons are planted in them. In greenhouses with soil heating and air heating, work continues year-round in 5–6 rotations: after early tomatoes, peppers, eggplants, early white cabbage, and cauliflower, cucumbers or tomatoes are planted, and in the autumn-winter period — green crops. With year-round use, organic fertilizers for pepper seedlings and eggplants are applied immediately before cultivation.

Improving the structure and physical properties of the soil

When growing bare-root seedlings in plastic greenhouses in the central regions on chernozems, there is no need to use added soil. It is sufficient to improve the physical and water-related properties of the local soil using accessible materials. Optimal soil parameters for the development of the root system of seedlings are:

• bulk density — 0.8–1 g/cm³;
• porosity — not less than 60%;
• organic matter content — 10–15%;
• structure — small-crumb (aggregate size 3–5 mm, fraction of particles up to 10 mm — no more than 15%);
• mechanical composition — light loam or sandy loam.

Organic fertilizers accelerate soil warming, stimulate plant growth in the early spring period, and activate beneficial microflora at lower temperatures. To improve the structure, in addition to humus, one can use peat or chopped straw in an amount of up to 30% of the soil volume. A small-crumb granular structure with a particle size of 3–5 mm allows for precise sowing depth, uniform emergence, and optimal conditions for growth.

It is best to grow seedlings on light soils, as they warm up and ripen faster. Heavy soils become waterlogged, which delays sowing, leads to uneven emergence, painful root breakage during harvesting, and increases the percentage of stunted plants. To improve the physical properties of heavy soils and accelerate their warming, agronomists use a phased preparation scheme.

1. Apply sand in autumn when the soil is in a state of physical maturity, and thoroughly incorporate it with a tiller.
2. In the spring, two weeks before starting greenhouse operation, cover it with plastic and turn on the heating to warm the soil and bring it to physical maturity.

Such soil condition disrupts the straightness of sowing, leads to uneven sowing depth of seed">sowing depth of seed, significant scattering in the row, and reduces the marketable yield of transplants by 50%.

To dry out the soil, it is not enough to just cover the greenhouse with plastic film 10-15 days before starting work. You must open the ventilation openings. If they are closed, a closed cycle of moisture occurs in the greenhouse: it evaporates from the soil surface, settles on the surface of the film, and, dripping down, returns to the soil.

Mineral nutrition. By applying mineral fertilizers, it is possible to improve the biometric indicators of transplants and their chemical composition by increasing the content of phosphorus and potassium relative to nitrogen, as well as to increase the activity of physiological processes, transplant survival, photosynthetic potential, leaf productivity, and early and total harvest.

The optimal nutrient content for tomato, pepper, and eggplant transplants in soils is: with the application of straw and peat — 20-25 mg of nitrogen, 4-8 mg of phosphorus, 15-20 mg of potassium per 100 g of soil (determined in an aqueous extract); with the application of humus — 15-25 mg of nitrogen, 20-30 mg of phosphorus, 20-35 mg of potassium per 100 g of soil.

When using straw in the soil, in addition to the base application rate of mineral fertilizers, 10 kg of this element per 1 ton of straw should be applied to compensate for the nitrogen consumed by microorganisms during the decomposition of organic matter.

The lower limit of nutrient content, at which the quality of transplants sharply deteriorates, should be considered 5-7 mg of nitrogen, 1-2 mg of phosphorus, and 4-10 mg of potassium, and the upper limit — 100-120 mg of nitrogen, 50-70 mg of phosphorus, and 160-180 mg of potassium per 100 g of soil.

Approximate doses of mineral fertilizers in the absence of soil chemical analysis results are provided in the corresponding growing technologies for transplants">growing technologies for transplants.