Optimal conditions for vegetable crops in a protected environment

SOIL IN RELATION TO LIGHT, HEAT, MOISTURE, AND AIR

One of the difficult issues of year-round hotbed utilization is the lack of natural light, especially during the period of November-December, when the days are shortest and often overcast. The lack of light has a sharp impact on the harvest, especially for crops that are demanding of light.

For example, according to numerous experiments, cucumbers when grown during the January-July period yield about 100 pieces per m², in August-September — 20 pieces, in September-December — 7-8 pieces, and often do not grow at all.

harvest also during the November-January period (with a decrease of 25—50%);

Regarding the light requirements, plants are classified as follows:

Beet for greens from seed. 8. Lettuce.

Plants less demanding of light: 1, Onion for scallions.

Parsley for greens from roots.

Beet for greens from roots.

Radish, 2, Dill. 3. Spinach,

Plants that produce a harvest in the absence of light:

By selecting these plants for cultivation during different times of the year, it is possible to achieve year-round operation of a hotbed-greenhouse facility. This is especially achievable through the use of supplemental electric lighting in greenhouses.

The best utilization of natural light is achieved by the correct positioning of hotbed and greenhouse structures, as mentioned above. Here, increasing the glazed area by reducing shading parts (bars, excessive putty), keeping frames in order and clean (removing debris and dust from the glass, etc.), setting the correct tilt angle for hotbed frames, slopes of greenhouses, good quality glass, etc., are of great importance.

\F. M. Yudkin, "Vegetable cultivation in greenhouses and hotbeds" — Selkhozgiz, 1939.

Among the components of ambient air, carbon dioxide is of the greatest importance for plant development. In hotbeds, the source of this gas is biological fuel, which releases enough carbon dioxide during its decomposition. In greenhouses using technical, flue, and other heating methods (non-biological fuel), the need for carbon dioxide is covered by the air entering from the outside (during ventilation), as well as by burning wood in greenhouses with flue heating after closing the chimney.

Regulation of the thermal regime in hotbeds with biological fuel heating is carried out by covering the hotbeds with frames and mats and by ventilation when opening the frames. For better control over the thermal regime, it is necessary to have thermometers.

Among vegetable crops, there are plants that are more heat-loving and cold-resistant. The group of plants requiring a higher thermal regime includes cucumbers, tomatoes, summer squash, etc. For them, the most favorable temperature is 18—25° depending on the time of year, time of day, and phase of development. Less demanding of heat are radish, spinach, transplants of rutabaga and cabbage. They require a temperature in the range of 6—18°.

Onion for scallions, lettuce, dill, and others can develop well at both high and low temperatures.

Most vegetable crops consume a large amount of water during their development. At the same time, water evaporation by the leaf surface of plants is also high. The plant spends a lot of solar energy on evaporation, up to 80% of all the energy received by the plant. It is necessary to regulate the thermal and water regimes so as to reduce these expenditures of solar energy by the plant to a minimum. Excessive evaporation leads to wilting and a reduction in leaf surface, which leads to a decrease in yield.

For better water availability for plants, hotbed soil should have up to 60% humidity. If there are no special instruments, soil moisture is practically determined as follows. At a soil depth of 5—7 cm, take a handful of soil and squeeze it in your fist. If the clod does not fall apart, then the soil is sufficiently moist and does not require irrigation. If the clod crumbles, then the soil is not sufficiently moist and needs to be irrigated.

To calculate the water requirement for irrigation, you can proceed from the following data:

Approximate amount of water for irrigation of one frame per day by months

March — 1.5 L, April — 3.2 L, May — 5.9 L, July — 7.5 L, August — 4.5 L.

In order to prevent cooling of the soil, it is best to irrigate the land with water at the same temperature as the hotbed or slightly higher.