عنوان مقاله [English]
Under plastic tunnels high thermal and humidity conditions for early ripening might cause fungal diseases, which enforce cucumber growers to use fungicides. Use of natural aeration in perforated plastic tunnels could reduce fungal diseases onset. The aim of this research is to evaluate thermal and humidity relations within cucumber plastic tunnels. For this purpose three microclimates of 1) closed plastic (MC), 2) perforated plastic with 100 holes of 10 mm diameter per m2 (MP10), and 3) perforated plastic tunnels with 100 hole of 15 mm diameter per m2 (MP15) were employed as experimental treatments in a complete randomized block design with three replications. Cucumber seedlings were grown on late February within high tunnels of 3.3 m width, 1.7 m height and 6 m length in Mahmoudabad, Mazandaran. The results showed that the daily mean and maximum temperatures with tunnels always were higher and significantly different from open air. Cumulative degree-day was significantly higher within MC, relative to other microclimates. No difference was observed for daily mean and minimum relative humidity in MP10, MP15 and open air. Total cucumber harvest was 12 and 20 percent higher in MC relative to MP10 and MP15, respectively. In conclusion, perforated plastic tunnels provide a modified environment for cucumber; meanwhile MP10 tunnels yield reduction could benefit environment safety regulations.