Relationships between air relative humidity and soil temperature in open-field tomato production

M. Dallev¹ and G. Hristova²*

¹Agricultural University of Plovdiv, 12 Mendeleev Blvd, BG4000 Plovdiv, Bulgaria
²Trakia University, Faculty of agriculture, Department of Agricultural Engineering, Student City, BG6000 Stara Zagora, Bulgaria
*Correspondence: galina_jam@yahoo.com

Abstract:

Understanding microclimatic interactions between atmospheric and soil parameters is essential for precision agriculture and irrigation management. The present study evaluated the relationships between air temperature, relative humidity, soil temperature, and soil moisture under open-field tomato production using a portable ESP32-based monitoring system. Measurements were conducted at ten field points with three replicates per point (n = 30). Descriptive statistics indicated relatively stable environmental conditions during the observation period. Pearson correlation analysis revealed a statistically significant inverse relationship between air relative humidity and soil temperature (r = -0.376, p = 0.040), while no significant linear relationships were observed between the remaining variables (p > 0.05). Linear regression analysis confirmed that increasing air relative humidity was associated with decreasing soil temperature (R² = 0.142, p = 0.040), although the explanatory power of the model remained limited. Validation against a Meteobot® reference weather station demonstrated high accuracy of soil temperature measurements (relative error 0.74%) and acceptable performance for soil moisture (6.28%). The results indicate that low-cost IoT-based monitoring systems can reliably capture microclimatic interactions under field conditions and support their application in precision agriculture.

Key words:

air humidity, microclimate monitoring, regression analysis, soil temperature

Air-conditioning in the cabins of passenger

S. Kumar*, J. Cerny and P. Kic

Czech University of Life Sciences Prague, Faculty of Engineering, Department of Technological Equipment of Buildings, Kamýcká 129, CZ165 21, Czech Republic
*Correspondence: surenderduhan88@gmail.com

Abstract:

The objective of this paper is to analyse the current state of the constructional design and operational conditions of air-conditioning device in passenger cars. The research was focused on the function of air-conditioning equipment of passenger cars Skoda and KIA in various modes of operation during the winter, spring and summer season at different levels of air conditioning (without air-conditioning, minimum, medium and maximum level). Air temperature, air humidity, globe temperature, CO₂ concentration, dust concentration and noise inside the cabin were measured. Solar radiation plays a big role to rise up temperature inside the cabin. It resulted in the higher values of globe temperature than temperature of the air. The results of the measurements showed that CO₂ values were significantly lower than 2,500 ppm at minimum air-conditioning, lower than 600 ppm at medium and lower than 500 ppm at maximum level of air-conditioning. For all vehicles, dust concentration was greater when it measured with the air conditioning switched off than with the air conditioning system turned on. The measurements confirmed that the total dust concentration was not more than 47 μg m^-3, PM₁₀ lower than 28 μg m^-3 and PM₁ lower than 27 μg m^-3. The noise levels ranged from 49.1 to 68.7 dB(A). The air-conditioning had very positive impact on the inside comfort in car cabins from all points of view during all periods of the year.

Key words: