Determination of the effect of different polycarbonate greenhouse cover materials on environmental microclimate and plant development with thermal cameras

In this study, it was aimed to determine some physical and mechanical properties of different Polycarbonate (PC) greenhouse cover materials and to investigate the effects of these materials on the indoor environmental conditions. In addition, the mechanical properties of the cover materials and the imaging of the ambient microclimate via thermal cameras and their effects on plant growth were investigated. In the study, the total radiation transmittance and photosynthetic effective radiation (PAR) transmittance were determined as the physical properties of greenhouse cover materials. The yellowing index and impact strength were determined as the mechanical properties of the greenhouse cover materials used in the study and measurements were taken from the test samples with a thermal camera every three months during the trial period. Tomato cultivation was carried out in the greenhouse between 2019-2020 and 2020-2021 spring terms to determine the effects of radiation permeability of different greenhouse cover materials on the plant growth, development, yield and fruit quality and to determine this effect via a thermal camera. In the study, the greenhouse indoor and outdoor temperature and relative humidity values were monitored in order to determine the greenhouse indoor environmental conditions under different greenhouse cover materials. Therefore, the canopy temperatures and roof temperatures were monitored via the thermal camera. In the study, the initial total radiation transmittance of UV protected PC (UV PC), UV+IR protected PC (UV+IR PC) and sidewall UV protected PC roof PE (UV PC+PE) was determined as 49.4%, 49.2% and 62.6%, and decreased by 25.1%, 28.9% and 10.7%, respectively at the end of the study period. It was determined that the initial PAR permeability of UV PC, UV+IR PC and UV PC+ PE greenhouse cover materials was 54.7%, 49.3% and 54.1%, and decreased by 27.2%, 25.6% and 9.4%, respectively at the end of the study period. In the study, the initial yellowing index values of UV PC, UV+IR PC and UV PC+PE greenhouse cover materials were determined as -1.46, 4.41 and -1.28, respectively. As of the 21th month, the yellowing index values were determined as 18.4, 14.5 and 18.7 for UV PC, UV+IR PC and UV PC+PE, respectively. The initial impact strength values of UV PC and UV+IR PC greenhouse cover materials were 1203.4 and 1162.5 g, and the initial impact strengths decreased by 20.3% in the UV PC material, and increased by 6.3% in the UV+IR PC material, at the end of the study. In this study, in which the effects of different greenhouse cover materials on plant growth were examined, the highest yield was obtained from UV+IR PC greenhouse cover material in both years of cultivation when the total yield is taken into consideration. As a result, in this study, valuable information related the effects of PC greenhouse cover material on the indoor environmental conditions, the visualization of the mechanical properties of the cover materials and the ambient microclimate with thermal cameras, and the effect on plant growth have been revealed both in Turkey and in the regions with similar features across the world. Moreover, the necessity of using thermal cameras, enabling damage-free and contactless detection with the rise of technology, in many fields of agriculture has also been put forth.