Bell peppers (Capsicum annuum L.) grown under diffuse glass Christien Sauviller Research Centre Hoogstraten Meerle, Belgium
Pepper production in Belgium Bell pepper: red, green, yellow, orange Heated greenhouse Production: March -> November 126 ha = 311 acres Small family businesses 37,000 tonnes per year, 38 million Horticultural producer co-operatives North of Belgium: Hoogstraten, Mechelen
What is diffuse glass? Float glass: regular or low-iron Altered surface structure Incoming light is scattered 4 mm glass R A T I
What is diffuse glass? Degree of light scattering = haze percentage of the outgoing light that has undergone a change of direction of more than 2.5 relative to the incoming light I 2.5 O Higher haze: more light scattering, lower light transmission Optimal haze: between 50% and 75%
What is diffuse glass? Alleged advantages: Better light penetration in the crop Positive for vertically growing crops e.g. pepper, tomato, cucumber Less shade Lower crop temperature Better red/far red ratio Promising results research The Netherlands in cucumber and tomato Hoped-for results: better production and fruit quality
Diffuse glass at RCH Pepper research: 5,000 m², 7 compartments 2 compartments of +/- 500 m² for research diffuse glass
Diffuse glass at RCH Regular glass Diffuse glass
Diffuse glass: Hortifuse 5.7 Van Looveren n.v., Belgium
Materials and methods: general Type of glass LT vertical LT hemispheric Haze Reference: Float 90.3 % 83.5 % -- glass 90+ (low iron) Hortifuse 5.7 91.7 % 79.8 % 58 % 2011 2012 Variety (red) Viper (Enza) Date of sowing 13 Dec. 2010 2 Nov. 2011 Date of planting 2 Feb. 2011 19 Dec. 2011 Cultivation system V-system, 3 stems per plant Density 2.37 plants/m², 7.1 stems/m² Start end harvest 20 Apr. 8 Nov. 4 Apr. on-going
Materials and methods: light PAR light: Photosynthetically Active Radiation (400-700 nm) Close to greenhouse roof - > transmission Different heights in crop (Above) yop of crop 60 cm-> 180 cm under top of crop - > light penetration in crop
Results: light PAR (mol m-2 day-1) top/depth 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 Proportional light penetration in crop Float 90+ glass Diffuse glass 0.55 0.51 0.31 0.27 60 cm below top 180 cm below top
Results: light PAR (mol m-2 day-1) 25.0 20.0 15.0 10.0 5.0 PAR 1 m below top greenhouse Float 90+ glass Diffuse glass 0.0
Results: light PAR (mol m-2 day-1) 25.0 20.0 15.0 10.0 5.0 PAR at different depths in crop Float 90+ glass Diffuse glass 0.0 Jun./30 Jul./1 Jul./2 Jul./4 Jul./5 Jul./6 Jul./8 Jul./9 Jul./10 cm 60 60 60 120 120 120 180 180 180
Materials and methods: photosynthetic capacity University of Ghent (UGent) Light intensities: 0 -> 1800 PAR µmol m-2 s-1 Leaves at different depth in crop: 30 cm, 100 cm, 150 cm below top of crop May, September 2012
Results: photosynthetic capacity Net photosynthesis (µmol CO 2 m-2 s-1) 25.0 20.0 15.0 10.0 5.0 0.0-5.0 Light response curve Float 90+, -30 cm Diffuse, -30 cm Float 90+, -100 cm Diffuse, -100 cm Float 90+, -150 cm Diffuse, -150 cm 0 500 1000 1500 2000 PAR (µmol m-2 s-1)
Materials and methods: leaf temperature Leaf at top of plant, not shaded IRtc sensor and RHT sensor
degrees Celcius 40 35 30 25 20 15 10 5 0 Results: leaf temperature Leaf temperature, 11/Mar. 2012, sunny day Float 90+ glass Diffuse glass Temperature not always lower when sunny
Materials and methods: crop development + results Length, fruit set, leaf size Type of glass Length (cm) Number of fruits set Length leaf (cm) 2011 Width leaf (cm) Float 90+ 315 a* 140.6 a 12.3 a 6.6 a Diffuse 305 a 146.6 a 12.8 a 7.0 a * T-test, P 0.05 2012 Type of glass Length (cm) Number of fruits set Length leaf (cm) Width leaf (cm) Float 90+ 337 135.4 11.8 6.4 Diffuse 343 137.3 12.1 6.4 Statistic tests still to be carried out
Materials and methods: yield and fruit quality Yield: kg/m², number of fruits, fruit weight Harvest frequency: 1 to 2 times a week 2011: 20 Apr. 8 Nov. 2012: 4 Apr. on-going Grading size: diameter of shoulder in mm, +55 mm -> + 105 mm Grading fruit quality: Flandria (best), class I, class II, unmarketable Fruit quality: sunscald, blossom end rot, ripeness spots
Results: yield Yield 2011: 20 Apr. 8 Nov. Type of glass * T-test, P 0.05 Kg/m² % Number of fruit Grading (size) 2011: 20 Apr. 8 Nov. Fruit weight (g) Float 90+ 28.3 a* 100.0 140.6 a 202 a Diffuse 29.1 a 102.8 146.6 a 198 a Type of glass +55 mm +63 mm +73 mm +83 mm +95 mm +105 mm Float 90+ 0% 2% 22% 65% 10% 0% Diffuse 0% 4% 25% 61% 10% 0%
Results: yield Yield 2012: 4 Apr. 24 Oct. Type of glass Kg/m² % Number of fruits Statistic tests still to be carried out Grading (size) 2012: 4 Apr. 24 Oct. Fruit weight (g) Float 90+ 26.4 100.0 127.6 207 Diffuse 25.7 97.1 128.0 200 Type of glass +55 mm +63 mm +73 mm +83 mm +95 mm +105 mm Float 90+ 0% 1% 9% 72% 18% 0% Diffuse 0% 1% 11% 75% 12% 0%
Results: fruit quality 2011: 27 Apr. 2 Nov. Type of Flandria Class 1 Class 2 Unmarketable glass Float 90+ 88.8% 6.5% 2.5% 2.2% Diffuse 88.2% 7.6% 1.8% 1.4% 2012: 28 Mar. 10 Oct. Type of Flandria Class 1 Class 2 Unmarketable glass Float 90+ 88.9% 6.5% 4.0% 0.6% Diffuse 90.0% 6.6% 2.9% 0.5%
Results: fruit quality 2011: 27 Apr. 2 Nov. Type of glass Sunscald 2012: 28 Mar. 10 Oct. Blossom end rot Ripeness spots Float 90+ 0.5% 0.2% 0.2% Diffuse 0.9% 0.6% 2.5% Type of glass Sunscald Blossom end rot Ripeness spots Float 90+ 0.4% 1.0% 0.2% Diffuse 0.2% 0.5% 0.0%
Conclusion Proportionally better light penetration in crop Slightly more light in deeper layers of crop, but only very small % of light above canopy > contribution to photosynthesis? No more light in top layers of crop > due to lower light transmission characteristics Younger leaves more efficient at high irradiation, older leaves equal to less efficient Leaf temperature lower when sunny, not always!
Conclusion Yield results inconclusive (2011 higher, 2012 lower) Fruit quality not better Cool summer 2011, summer 2012: august sunny, only 1 week hot Future for diffuse glass in greenhouse bell pepper? With anti-reflection (AR) coating? (compensate loss of light transmission) Without AR? Reduced use of screen for solar reflection? Cost diffuse glass: Float 90+ x 1.88 Cost diffuse glass + AR: Float 90+ x 4.41
Acknowledgements Flemish Government, Agriculture and Fisheries Policy area, Department Sustainable Agricultural Development
Thank you!