Effects of Root Zone Cooling on Lactuca Sativa Cultivation Under Roof Top Garden Structure in Tropical Climatic Conditions

A roof top garden structure was installed on top of a 20-foot freight container plant factory in MARDI Serdang, Selangor. The roof top garden consists of 3 major components which is a rain shelter, a reticulated hydroponic growing system via Nutrient Film Technique (NFT) and a chiller system to chill and control nutrient-water temperature in the fertilizer tank. Lactuca sativa was cultivated using root zone cooling, with a hydroponic setup at ambient temperature as control to study the effects of the root zone cooling system (RZC) on the crop yields in the tropics. The weight of crop, weight of root, leaf width and leaf numbers of Lactuca sativa have been selected as yield parameters, recorded and analyzed. From the results, all the growing parameters performance for Lactuca sativa grown in root zone cooling method were found to better compared to control. For yield parameters performance, Lactuca sativa grown in control were found to be better, compared to root zone cooling method. The yield weight for Lactuca sativa cultivated using control is higher than RZC system by 39.4 %, ranging from 36.69- 39.04 g using control and from 20.59-23.66 g by using RZC method. Roots weight for Lactuca sativa cultivated using control method is better than RZC by 14.1 %, ranging from 5.73- 6.22 g using control, meanwhile from 4.69-5.34 g by using RZC respectively. Number of leaves for Lactuca sativa cultivated using control method is more than RZC by 26 %, ranging from 14-15 using control and static at 11 by using RZC system. The leaves dimension for Lactuca sativa cultivated using control is bigger than RZC by 48 %. The range of Lactuca sativa leaves dimension cultivated using control method is from 580.35-670.27 cm2, meanwhile by RZC is from 318.68-348.45 cm2.   Keywords: root zone cooling; roof top garden; Lactuca sativa; tropics