1. 2 AVRDC – The World Vegetable Center, Taiwan
臺中區農業改良場
Taichung DARES, COA, EY
NCHU
EVALUATION OF SUMMER LIGHT INTENSITY BETWEEN THE EAST AND WEST SIDES OF A TWIN-SPAN GLASSHOUSE
Ling-Hsi Chen1, Tzu-Chih Shen2, Wuu-Yang Chen2, Jiun-Yuan Chen3, Chia-Chung Chen3, Jacqueline d’Arros Hughes2  
1 Taichung District Agricultural Research and Extension Station, Council of Agriculture, Executive Yuan, Taiwan
2 AVRDC – The World Vegetable Center, Taiwan
3Dept. of Bio-industrial Mechatronics Engineering, National Chung Hsing University, Taiwan
RESULTS
Introduction
Glasshouses with high structural strength, commonly used for growing orchids in Taiwan, are also suitable for cultivating tomato, sweet pepper, cucumber and melon.
Multi-span glasshouses share pillars and frames to reduce construction costs, but these structural elements and compartment walls may block the light needed to ensure even crop growth, yield and quality.
Objective
Evaluate the difference between the levels of photosynthetic active radiation (PAR) between the east and west sides inside twin-span glasshouses in the summer in southern Taiwan as a reference for planning future protected culture experiments.
Figure 2. The hourly average solar radiation data inside glasshouse were 31% and 43% of outside solar radiation on 24 August and 1 September, respectively.
Materials and Methods
Figure 1. (A) The twin-span glasshouse growing tomato and sweet pepper (B) PAR sensor (C) data logger.
(A)
(C)
(B)
Figure 3. The hourly average light intensity inside glasshouse from 20 Aug. to 2 Sept
Table 1. Statistics results of light intensity inside glasshouse in 5 different time spans from 20 Aug. to 2 Sept
Glasshouse: A twin-span glasshouse with compartment walls on the west side and 8 troughs planted with tomato and sweet pepper at AVRDC headquarters, Taiwan (E , N ).
Quantum sensor: Two sets of SQ-215, 0.5 μmol m-2 s-1 per mV, Apogee, USA, sensors were fixed at 2.2 m above ground in central part of 2nd and 7th troughs.
Data logger: One set of CR1000, Campbell Scientific, USA.
Data collection: Outside-the-glasshouse solar radiation data were collected from the AVRDC weather station. Inside the glasshouse, a compact weather station, HD (Delta Ohm, Italy) was used.
Observations: Made from 20 August to 2 September 2014.
Data analysis: All collected data were analyzed using Microsoft Excel and Sigmaplot software.
Table 2. Statistic data of photosynthetic active radiation inside glasshouse in 3 time spans (morning, midday and afternoon) from 20 Aug. to 2 Sept (Unit: mol m-2 s-1)
CONCLUSION
The light intensity inside the glasshouse was only 31-43% of the outside solar radiation, due to the shading effect of the glazing, steel frame, dust, outside screens, etc.
The greatest difference in light intensity between the east and west sides of the twin-span glasshouse occurred in the afternoon (20.02%). The daily average of the light intensity on the east side was 3.48% higher than the west side between 05:00-18:00.
If twin-span glasshouses are used for protected cultivation in southern Taiwan, care must be taken to minimize the effect of the light intensity resulting from the pillars, frames and compartment walls to maximize even development of crops for optimal productivity.
ACKNOWLEDGEMENTS
The authors thank the Council of Agriculture, Executive Yuan, Taiwan for financial support through grant No. 102AS ST-a3