General. Requirements of Plastic Films for greenhouse application Latest Development in Research 1/22/2009. Requirements. General

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1 Requirements of Plastic Films for greenhouse application Latest Development in Research 6 th European Additives & Colors Conference, 11/12 March 29, Antwerpen Silke Hemming, Wageningen UR Greenhouse Horticulture Requirements Covering materials for horticultural applications: High light transmission Optimum light spectrum Optimum heat input - low heat losses Optimum condensation behaviour High mechanical resistance Low sensitivity to ageing (UV, temperatures, chemicals) Fabrication sizes Costs General General Solar radiation (3-25nm), energy input greenhouse Relevant for horitcultural applications Global radiation UV PAR NIR absorption UV 3-4 nm morphogenesis PAR 4-7 nm photosynthesis, morphogensis FR 7-8 nm morphogenesis NIR 8-25 nm increasing greenhouse temperature FIR µm heat radiation UV PAR transmission greenhouse covering photosynthesis / growth Τ inside Τ crop Τ outside Heat radiation, energy loss greenhouse Philips 1

2 Global radiation UV PAR NIR absorption ventilation open transmission greenhouse covering CΟ 2 Τ outside UV PAR increasing temperature heat Τ inside Τ crop photosynthesis / growth Light transmission <<5% Light transmission >75% Tropics Spain The Netherlands Spain PAR transmission different materials transmission hemispherical [%] transmission perpendicular [%] Light measurement (a) Measure hemispherical light (b) 2

3 Photosynthesis Light quality 4-7nm photosynthetic active radiation Lightreceptors: chlorophyl, carotinoids Plants use theoretically all colours for photosynthesis Most plants use red light ( 65nm) and blue light ( 45nm) more efficiently Plants adapt to colours during growth Photosynthesis Morphogenesis Sensitivity of human eye = visible light 38-78nm Sensitivity of all plants = PAR 4-7nm 3-8nm Specific lightreceptors for UVB, UVA, Blue and Red:Far-red Elongation Side shoots Leaf area and leaf thickness Flowering Colour of flowers and leaves Germination Light quality Light quality UV influence on insects UV-transparent films influence: Hardening of crops; Leaf and flower colour (lettuce lollo rosso, aubergines, some flowers or flowering potplants); Compact growth (bedding plants, some potplants) Behaviour of insects (white fly, trips, louse, (bumble-) bee) Population growth of insects on chrysanthemum under different UV-transparant covers after 6 weeks louse white fly trips # mean s.d # mean s.d # mean s.d. Reproductiontest of insects on leaves indirect influence of UV (plant as food source) # larves Many other influence factors: temperature / humidity / light sanitation plant vitality glass PMMA PC 3

4 Light quality UV transmission of different materials transmission [%] UVB 6 UVA Light diffusion PE film with UV glass PE film traditional PE film with UV-blok wavelength [nm] Light diffusion Greenhouse covering materials are able to scatter light rays, transforming direct light into diffuse light Light diffusion 5% % Haze Vertical Horizontal light light distribution Most Cast shadow light intercepted from greenhouse by upper construction leaves elements Lower No uniform leaves growth contribute and less development to photosynthesis in greenhouse Background light interception Background - photosynthesis 4

5 Background - yield Yield cucumber 28 Materials haze and light transmission EVA film diffuse EVA film ETFE film diffuse 74% haze 27% haze % haze more fruits 9.2% 6.5% - ETFE film Horticultural glass hemispherical transmission haze [-] [-] Light Diffusing Covering Materials p- h y =.1145x R 2 = haze [-] Be careful with light losses at high haze factors Heat input Global radiation UV PAR NIR UV PAR Reflection by NIR-filter absorption transmission greenhouse covering photosynthesis / growth Vents can be kept closed for a longer period CΟ 2 heat Τ inside Τ crop Τ outside Experiment: inside NIR reflecting screen NIR-reflecting inside screen (8-11 nm) Screen: 4% reflection of NIR energy Crop: 45% reflectio of NIR radiation Installation parallel to roof Greenhouse climate control: Temperature Artificial lighting (1 micro mol m -2 s -1 ) CO 2 injection (1ppm) 5

6 Results: ventilation opening Results: crop ranspiration N-Vent open (%) NIR N-vent NIR S-vent REF N-vent REF S-vent Local time (hours) S-vent open (%) Transpiration (g m -2 h -1 ) NIR REF REF =.3x NIR =.28x Global radiation (W m -2 ) Transpiration VS global radiation outside NIR (g m -2 h -1 ) NIR =.88*REF REF (g m -2 h -1 ) NIR VS REF transpiration Results: crop development Tplant ( o C) NIR Tp REF Tp Local time (hours) NIR-filtering Northern Europe: Adaptable NIR-filtering screen outside (!) with high light transmission In closed greenhouse NIR-filtering reduces cooling capacity up to 3% Foto Ecofys Slower crop development in NIR due to lower temperature in NIR NIR-filtering Questions? Mediterranean Countries: In (unheated) greenhouses use of an (adaptable) NIR-filtering outside screen only in hot periods Tropical regions: NIR-filtering coverings reduce air and crop temperatures permanently Foto Ecofys 6