The Influence of the Height of Foil Tunnels on the Formation of Thermal Conditions in the Plant Growing Zone

The paper attempts to determine the influence of the height of foil tunnels on the formation of thermal conditions in the plant growing zone. A diagnosis of the temperature distribution and the direction of heat flow in the ground under tunnels was made. Continuous recording of the temperature and relative humidity of the internal and external air, the intensity of solar radiation and the direction and speed of the wind was also carried out. There are periods and places where there are losses and heat gains from the ground. Studies on the formation of thermal conditions in the ground and selected parameters of the internal and external microclimate were carried out in two free-standing tunnels of different construction, in an agricultural holding located in the Świetokrzyskie Province. In the tunnels, seasonal cultivation of cucumbers was carried out from April to October. In the hot bottom, the internal temperature in the higher tunnel was 6.8 °C lower than in the lower tunnel. On the other hand, on cloudy days, the temperature in both tunnels was similar, and its differences were within the scope of measurement error of the sensors. The studies did not show the influence of height on the temperature distribution in the root zone of plants. Differences in the top soil layer (−0.1 m) reached 0.8 °C. At lower levels (−0.5 m and −1.0 m), ground temperature differences under the tunnels were around 0.2 °C. The results of the detailed analysis indicate that, when taking the varied surface of the tunnels into account, the energy gains from the soil in the low tunnel reached 44.3 kWh/m2, whereas in the high one their value was higher and reached 46.4 kWh/m2.