Differences in Radiation and Temperature in Row Tunnels of Different Covering Materials

Abstract

The use of row covers/tunnels With polymers has made the controlling Of weather elements possible, yet the actual conditions mainly on spectral properties of covering materials, study adopted three of materials. nonwoven fabric (NWF), ordinary transparent polyethylene (PE), and UV-filtered polyethylene (UV-C), to analyze and monitor variations in radiation and temperature row tunnels of different coverings in the field. Results show that covering materials selected for the study have varied spectral properties but allow than in average. tested in laboratory. Of radiation transmitted through materials. Spectral properly Of CV-C plastic is similar to ordinary PE film, it absorbs rn0re than of ultraviolet (below 415 nm). NWF reflects (12.6%) more radiation than Others (PE 8.5%, UV-C 8.1%) but absorbs the least (0.4%. relative to 2 and for PE and UV-C respectively). Data further indicate that radiant energy and proportions of transmittance in various bandpasses have been changed after through the covering materials in the field. In average. transmittance was reduced 9.1, 18.3, and for PE (895% 10 81.4%), UV-C (SS. to 69.S%L and SWF (83m to respectively. UV region was again greatly filtered by UV-C following its spectral property. Correlation between irradiance and air temperature inside the tunnels was linear for materials, implying existence of greenhouse effect in the tunnels, The relationship of air temperature to soil was also linear and positively correlated, soil temperature was lowered In tunnels than in outdoor at the same air temperature due to the covering of silver plastic over the raised ked. 隧道式簡易設施近年來被廣泛被利用於栽培高經濟價值作物，其主要功能兼具氣象因子的調整及環境的保護。設施內的光輻射度之變化因被覆材質種類而異，直接影響設施內作物的生產。本文研究以設置於洋香瓜產（臺南縣東山鄉）之隧道式簡易設施探討不同被覆材質對設施內光輻射及溫度之影響，並追蹤與分析其季節變化。試驗選用非織性多元脂類之不織布（NWF）、一般透明聚乙烯塑膠布（PE）、及具有濾除紫外效果之透明聚乙烯塑膠布（UV-C）等三種不同材質參試，被覆隊道式簡易設施。根據實驗室測試結果，此三種被覆材質對光照平均吸收率甚低（7%以下），平均穿透率高於85%，平均反射率小於13%。NWF之反射率最高（12.6%），依序為PE（8.5%）、UV-C（8.1%）；吸收率則反之，NWF、PE、及UV-C分別為0.4、2、及6.8%。UV-C可顯著吸收415nm波長以下之紫外光輻射。此三種材質在田間之穿透率低於實驗室測值、不同波段之異動不一，顯示受到外環境之影響。以全波段（350-1100 nm）平均穿透率而言，PE、UV-C及NWF分別減少9.1、18.3、及19.2%，而UV-C材質在田間仍具有瀘除太陽光輻射中紫外光之效果。隧道式簡易設施內外之光輻射與氣溫呈現直級正相關，且在相同光輻射下施內氣溫高於外界氣溫，顯示此三種材質被覆之設內均具有溫室效應。又設施內外之氣溫與土溫亦呈現直線正相關，惟因設施內高畦面鋪蓋一層銀色膠布（polypropylene材質）阻隔熱量傳導入土壤，故在相同氣溫下設施內土溫低於未鋪蓋塑膠布之田間土溫。