Study of the Solar Transmissivity of Plastic Cladding Materials and Influence of Dust and Dirt on Greenhouse Cultivations

Effects of Cover Whitening Concentrations on the Microclimate and on the Development and Yield of Tomato (Lycopersicon esculentum Mill.) Inside Mediterranean Greenhouses

“…Using these spectrums, the total transmissivity of the materials was calculated (Figure 1b). Transmissivity of the plastic without whitening ranged between 0.61 and 0.91 (Figure 1b), in agreement with values measured in a new film (0.80-0.87) [55]. The transmissivity of the plastic with the control concentration of 0.250 kg L −1 was 0.33-0.52 ( Figure 1b) for the PAR wavelengths, corresponding with the values measured in a dirty cover with 6-month-old material without cleaning [55].…”

“…Transmissivity of the plastic without whitening ranged between 0.61 and 0.91 (Figure 1b), in agreement with values measured in a new film (0.80-0.87) [55]. The transmissivity of the plastic with the control concentration of 0.250 kg L −1 was 0.33-0.52 ( Figure 1b) for the PAR wavelengths, corresponding with the values measured in a dirty cover with 6-month-old material without cleaning [55]. From measurements of the quantity of the CaCO3 deposited in the plastic cover ( Figure 2a) and using the light transmitted spectrums (Figure 1), the total transmissivity of the materials was calculated over the PAR 400-700 nm, the 380-400 nm, and the 700-780 nm ranges ( Figure 2b).…”

“…This reduction does not seem to be proportional to the dose of calcium carbonate applied ( Table 2). The causes of the irregularity in shading were the heterogeneity of the application on the cover surface and the non-uniform effect of rain washing [32,39,55]. The transmissivity of the greenhouse cover with the different doses ( Table 2) differed of that measured in the plastic samples (Figure 1b), as a consequence of the effect of dirty accumulation [55], variation of sun position with time, and application heterogeneity [55].…”

“…During this study, the effect of an agricultural solar protector (ASP) applied at different concentrations (Table 1) was evaluated. We used three concentrations recommended by the manufacturing companies of ASP [55], which were selected based on the range of whitening concentrations used by the growers of Almería [19]. A concentration of 0.250 kg L −1 , mainly used by growers of Almería [19], was used as control in the west sectors of both greenhouses.…”

“…The causes of the irregularity in shading were the heterogeneity of the application on the cover surface and the non-uniform effect of rain washing [32,39,55]. The transmissivity of the greenhouse cover with the different doses ( Table 2) differed of that measured in the plastic samples (Figure 1b), as a consequence of the effect of dirty accumulation [55], variation of sun position with time, and application heterogeneity [55]. From measurements of the quantity of the CaCO3 deposited in the plastic cover ( Figure 2a) and using the light transmitted spectrums (Figure 1), the total transmissivity of the materials was calculated over the PAR 400-700 nm, the 380-400 nm, and the 700-780 nm ranges ( Figure 2b).…”