More light and lower temperatures with reflective shade screens vs. black shade cloth

Oct, 2014: Remarkable differences in both water and leaf temperatures in combination with more light is the conclusion of a trial made at a hydroponic lettuce grower in Thailand, comparing shading screens with black nets. The result makes the choice of screen in hot climates quite simple.

Hydroponic lettuce grower, Miss Veggie, located near Bangkok, Thailand produces salad for high-end Thai supermarkets and hotels. The company’s salads are processed and pre-packed at a facility in downtown Bangkok. Hydroponic vegetables face a growing demand because of the freshness of the product, the elongated shelf life and their clean appearance. To fulfil the growing demand production runs year-round. Demand peaks during early summer months, which unfortunately is the period with low production figures due to natural conditions. During this period and April in particular, average day temperature reach 33°C and 28°C ny night.

With the hydroponic growing technique a nutrient-rich stream of water flows directly along the roots. This water slowly heats up throughout the day, which negatively impacts the actual growth. Temperatures above 32°C are known to create substantial problems, in the month of April water temperatures at Miss Veggie can reach 35°C - causing severe production and quality losses.

To offset these warm water temperatures a trial was conducted to reduce heat  build-up in the system. The trial compared SOLARO 6720 O E WB, Svensson’s white, reflective shading screen with an ordinary local black shade net. Two lettuce crops, transplanted on the same day, were compared with one another. After 17 days remarkable results were noted.

Time

Outside

Inside radiation

Leaf temp

Water temp

Screen temp

 

Temp

Rad.

 Black net 

 SOLARO 

 Black net 

 SOLARO 

 Black net 

 SOLARO 

 Black net 

 SOLARO 

9 AM 

31

600

100

120

30,7

26,2

27,8

26,9

59

45

12 PM 

34

930

170

185

33,7

29,2

29,8

27,9

72

52

3 PM 

35

720

135

145

34,0

29,7

31,8

28,9

59

45

6 PM 

32

150

26

30

31,7

27,8

32,5

29,1

59

45

The radiation, leaf, water and screen temperatures  were measured periodically on hot and sunny days. In the trial, SOLARO 6720 O E WB was used as shading screen.

Remarkable differences were noted between the two treatments. Both the leaf temperature and the water temperature were found to be considerably lower under SOLARO, compared with the black shade - despite the fact that SOLARO transmits 10% more light. Results proved the reflective SOLARO shading screen to be a much better shield against the heat of the sun. This is clearly illustrated by the dramatic difference in screen temperatures, SOLARO temperatures were found to be 14 to 20 °C lower than that of the black shade.

Crop results
The crop results clearly reflect the above differences: Plants under SOLARO had a 40% higher weight, 53 g vs 31 g - Plant losses under SOLARO were reduced from 15 to 5%.

Conclusion
Thanks to the application of the reflective SOLARO shade screen Miss Veggie now benefits from more light with lower crop and water temperatures  than with traditional black shade nets. As well as a 40% boost in production weight. These results contribute to a more reliable year-round production schedule and a higher quality crop.

missveggie_1

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