Soft soil in rice field has a hardpan layer of less than 0.3Mpa. The usage of farm mechanization in rice field cannot be performed due to the hardpan structure cannot accommodate the load of heavy machinery. To overcome this problem, the method of soft soil replacement is used in order to revitalize the hardpan layer which has been damaged due to the stagnant water problem. Field study was conducted to test the soft soil replacement method to solve the problem of land on soft soil plot in Alor Senibung. A total of 4 plots have been prepared for the experiments where the top layer of paddy soil has been removed and replaced with other soil. After the soil has been compacted, the hardness of the hardpan was measured from time to time and is presented in this paper. The results from this study are expected to overcome the soft soil problems.

Nutrient film technique (NFT) is a hydroponic technique, whereby a very shallow stream of water containing all the dissolved nutrients required for plant growth is re-circulated past the bare roots of plants in a watertight gully, also known as channels. Problems commonly associated with NFT hydroponic system such as water temperature, can easily increase under direct sunlight in the tropics region, especially in the roof top garden, that can affect the quality of fertiliser used to cultivate the crop. Therefore, a study to develop a cooling system for NFT hydroponic technique is significant to control the water-dissolved nutrient temperatures suitable for crop growth. This paper highlights the studies conducted on fertiliser concentration distribution in the NFT hydroponics root zone cooling (HRZC) system for Lactuca sativa cultivation on roof top garden under the influence of water temperature, air temperature, relative humidity and ambient carbon dioxide. The fertiliser concentration distribution is determined by taking the electric conductivity (EC) reading of the fertiliser flowing along the NFT channels within three targeted points (left, middle, right) atfour different height levels of the cultivation beneath the roof top garden. The EC readings of the fertiliser remained steady, except for the tank along the levels from left, middle and right locations ranging from 1.64–1.66 µS. The water temperature, air temperature, relative humidity and ambient carbon dioxide fluctuated along these three points ranging from 20.50–22.80°C, 31.39–32.23°C, 67.06–68.65%, and 459.39–472.13 ppm, respectively. It was found that under the influence of those environment parameters and NFT root zone cooling system with different level and height, the fertiliser concentration distribution from point to point of data taken is not significantly different along the NFT channels. This finding is significant that integration of NFT root zone cooling system is an alternative to Lactuca sativa cultivation on roof top garden, despite the affecting surrounding temperature that may affect the quality and quantity of fertiliser and crops cultivation. This technique can be extended for the cultivation of other hydroponic vegetables, rice and flowers and promote the culture of roof top farming in the society to avoid the highly polluted soil on the ground environment that may bioaccumulate into the plant system that may ended up as a health threat to fellow consumers.

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

A plant factory has been developed at Horticultural Research Centre, MARDI Serdang. The cultivation approach under the plant factory consists of nine units planting racks with each rack having seven tiers or levels that can cultivate up to 900 crops per rack. Each unit of planting racks has been installed with electrical conductivity (EC) and pH monitoring system. EC is a meaningful indicator of water quality, soil salinity and fertilizer concentration. In this study, the data for EC and temperature were taken for each level different locations (three points along the rack) to evaluate the fertilizer quality distribution. The objective of the study was to evaluate the effectiveness of EC and temperature distribution on the planting rack of vertical farming system under the plant factory. From the study, it was found that EC and temperature parameters were not significantly different at each level and the point location of the vertical farming system. EC and temperature parameters were significantly different with the time (week) and point location from week to week. The effect of the interaction between time (week) and level on EC and temperature parameters were not statistically different. Therefore, it can be concluded that the effect of EC and temperature distribution at different levels of the vertical farming system did not depend on the time.