Greenhouse It is a relatively closed environment, and moisture management refers to the rational and effective regulation of environmental moisture within the greenhouse, primarily to control air relative humidity and temperature. Optimal air humidity and temperature can promote crop growth, and the main method of regulation is to control irrigation volume. Below Runtian Irrigation the technician Let me explain how to adjust irrigation for tomatoes in greenhouses to maintain appropriate relative humidity and temperature inside the structure.

Greenhouse Tomatoes

I. Regulation of Air Humidity in Greenhouses

Greenhouse air typically has a relatively high relative humidity, especially during the cold winter months when ventilation is limited; under these conditions, the relative humidity usually ranges from 80%— 90% Above, from dusk to morning can be achieved. 100% and reach saturation. The relative humidity of the air inside the greenhouse is influenced by soil moisture, greenhouse structure, and meteorological conditions. The higher the soil moisture, the higher the air humidity in the greenhouse. ; Greenhouses with good airtightness have relatively high air humidity, while those with poor airtightness have lower air humidity. ; Low, small greenhouses have high air humidity, while tall, large greenhouses have low air humidity. ; On cloudy and snowy days, relative air humidity is high; on sunny days, it is low. Among the many factors that influence air humidity, irrigation plays the dominant role. Traditional ground irrigation methods such as furrow and bed irrigation in greenhouses increase indoor relative humidity, whereas modern drip irrigation, subsurface drip irrigation, or mulch-under irrigation help maintain a relatively stable level of indoor relative humidity, thereby effectively reducing the incidence of tomato diseases and pests.

　　1 Scientific irrigation, while meeting the water requirements of tomatoes, seeks to minimize both the volume and frequency of watering in greenhouses, thereby controlling soil moisture levels and reducing the source of water evaporation, which in turn lowers the relative humidity within the greenhouse.

　　2 Ventilation for dehumidification and cooling aims to reduce temperature, remove excess moisture, and ensure air exchange. For long-season tomato cultivation, during autumn and summer the primary objectives of ventilation are cooling, dehumidification, and air exchange; therefore, ventilation should be prolonged and the vents opened wide. Depending on weather conditions, ventilation can be initiated when temperatures reach the upper limit for tomato growth and continued until sunlight no longer directly illuminates the greenhouse roof, thereby preventing the formation of additional water vapor inside the greenhouse after the vents are opened. In winter and early spring, the focus of ventilation shifts to air exchange and dehumidification; vents should be kept small and ventilation periods brief, while careful attention must be paid to heat retention. Ventilation is best carried out during midday on clear days, and vents should be promptly opened as temperatures begin to drop. Even on overcast days, appropriate ventilation for dehumidification and air exchange should be conducted around midday.

　　3 1. Plastic mulch: Plastic mulching not only reduces water evaporation, lowers indoor humidity, and improves water-use efficiency, but also raises soil temperature, thereby promoting the growth and development of tomato root systems.

　　 4. Implement insulation and dehumidification measures, strengthen management, and appropriately remove the straw mats to raise the greenhouse temperature, which can effectively reduce the relative humidity of the air inside the greenhouse. Typically, when the absolute humidity remains constant—that is, when the relative humidity inside the greenhouse is 100% At that time, for every increase in greenhouse temperature 1 ℃, relative humidity can decrease 5% left and right ; If the temperature inside the greenhouse is 5 — 10 At ℃, for every increase 1 ℃, relative humidity can decrease 3% — 4%。

　 II. Soil Moisture Management Techniques

　　 Tomato plants have high water requirements, but their root systems possess strong water-absorbing capacity, necessitating that soil moisture levels remain at 60% — 85% to the appropriate degree. The relative humidity of the air is 50% — 65% Growing up at the time Compare Okay. Tomatoes have different water requirements at different stages of growth. During the germination stage, the soil relative humidity should be 80% Around, the seedling stage and the flowering stage are earnestly requested. 65% Left and right, earnest plea during the result period 75% — 80%。

　　 Both excessive and insufficient soil moisture in greenhouses can hinder the normal growth and development of tomatoes; prolonged excess moisture can reduce soil oxygen levels, leading to root rot. ; Inhibits root elongation, results in shallow root distribution, and a small root mass. ; During cold seasons, excessive soil moisture can lead to a drop in soil temperature, inhibiting root activity and the decomposition processes carried out by soil microorganisms, thereby reducing fertilizer use efficiency. Excessive moisture during the seedling and vegetative growth stages can promote excessive vegetative growth. Conversely, insufficient soil moisture can cause wilting, and under intense sunlight, plants are prone to sunburn and leaf rolling.

　1 , Watering Method

　　 Adopting pipeline irrigation not only conserves water but also significantly reduces water losses during conveyance. ; Second, it saves land by reducing the footprint of ditches. ; Third, it is easy to use and highly adaptable.

　　 Irrigation can be carried out by subsurface drip irrigation under plastic mulch or by furrow irrigation. It is generally recommended to irrigate on a sunny morning, applying water to half of each furrow at a time, and to ensure adequate ventilation after irrigation to reduce indoor air humidity. ; Adopt raised-bed double-row planting with a central irrigation furrow; cover the bed surface with plastic mulch and irrigate through subsurface furrows to reduce water evaporation and lower air humidity. Implement subsurface drip irrigation, which saves water and labor, ensures uniform irrigation, does not damage soil structure, and maintains good soil permeability. Subsurface infiltration irrigation, in the cultivated soil layer 10 Install seepage pipes at a depth of several centimeters, allowing tomato roots to quickly access water while keeping the soil surface relatively dry and the cultivated topsoil consistently moist. During this period, the cultivation aisles can be mulched with wheat straw to reduce soil moisture evaporation.

　　2 , Irrigation Period

　　 During the seedling-raising stage, water management primarily aims to prevent substrate drought. Typically, sufficient water is applied at sowing. After emergence, watering is restricted to inhibit excessive vegetative growth and promote root development; irrigation should be adjusted based on seedling condition, substrate moisture content, and weather conditions. Generally, 3 — 5 Water the plants once a day, ensuring each watering thoroughly saturates the growing medium. When transplanting, water thoroughly to promote root establishment and help the seedlings acclimate. After the seedlings have recovered, water once before flowering, and simultaneously carry out shallow cultivation and hardening-off. After transplanting, watering is generally not recommended; if the soil is dry, a light misting may be applied. Avoid frequent watering—wait until the first flower cluster has set fruit before applying additional fertilizer and watering. Watering too early can easily lead to flower and fruit drop; typically, at the… 1 The fruits rapidly expand in diameter to 3 — 4 Centimeters, the 2 Squatting can be halted when the fruit begins to swell.

　　 During the flowering and fruit-setting stage, when outdoor temperatures are high, it is advisable to water frequently with small amounts; typically, 7 Water once every few days, 667 Square meters per pour 7 Around one cubic meter of water. In the future 7 — 10 Water once a day, 667 Square meters per pour 8 — 10 Cubic meters of water. 10 Watering should be moderated after mid-month.

　　 Reduce watering after November, every 20 — 30 Water the plants once a day, 667 Watering per square meter 10 — 15 cubic meters. The following year 4 After the month, as temperatures rise, irrigation is increased. 7 About once every few days, 667 Watering per square meter 10 Approximately cubic meters. From planting to uprooting, a total of water was applied. 20 — 25 This time, the total irrigation water volume is 300 — 340 Cubic meter.

　　 III. Irrigation Timing

　　 The timing of irrigation is primarily determined by the water requirements of tomatoes at each growth stage; additionally, factors such as seedling vigor, soil temperature, and weather conditions (cloudy or sunny) must also be taken into account.

　　 1. Determine the watering schedule based on the seedlings’ condition: The seedlings’ growth can indicate whether the soil is lacking moisture. If the seedlings show no wilting at noon, it means the soil is overly moist; if they exhibit a slight wilting at noon but recover by the afternoon, 3 — 4 If the seedlings return to normal shortly after watering, the soil moisture is appropriate; if they still have not recovered by sunset, it indicates severe soil drought.

　　 2. Determine watering time based on soil temperature: Water when the soil temperature is high, as moisture evaporates quickly and tomatoes absorb more, typically preventing the soil from becoming overly wet. 10 Centimeter soil temperature is 20 Watering is appropriate when the temperature is above ℃; when the soil temperature is below 15 ℃ Water cautiously, and when necessary, apply small amounts of water; soil temperature is at 10 Stop watering when the temperature is below ℃.

　　 3. Determine watering times based on weather conditions: Water in winter should Water on a sunny morning. Pretty good On sunny days, both soil temperature and air temperature are relatively high, so after irrigation the greenhouse can be sealed to retain heat, preventing a significant drop in soil temperature. However, when prolonged cloudy weather gives way to sudden sunshine, soil temperature remains low, making irrigation difficult; in such cases, foliar spraying can be used to supplement water.

　　 4. Do not water on cloudy days or in the afternoon. Pretty good 。