Indoor production of loose-leaf lettuce (Lactuca sativa L.) using artificial lights and cooling system in tropical lowland

Abstract

In the Philippines, crop production hindrances are climate change effects, typhoon occurrences, seasonal dependent cropping pattern and decreasing farm areas. There is a need to strategize farming technologies. Controlled environment agriculture (CEA) has potential in addressing these issues. A farming set-up in controlled environment was developed using locally available materials, light emitting diodes (LED) as sole-source of light and cooling system for temperature manipulation. This study was conducted to benchmark temperature and light intensity requirements for growing loose-leaf lettuce in lowland tropics. Light intensities of 50, 100 and 150 μmol m-2 s-1 were tested under temperature settings of 25 °C and 18 °C. Carbon dioxide and relative humidity were maintained at recommended levels. In actual chamber condition, average day/night temperatures inside were 25.3±0.4/25.5±0.2 °C and 18.9±0.6/18.7±0.3 °C, for the first and second cycles, respectively, whereas, day/night temperatures outside chambers were 29.6±2/25.9±0.5 and 26.2±1/23.6±0.6 during the first and second cycles, respectively. Under two temperature settings, best yield per unit area was observed at required light intensity of 150 μmol m-2 s-1. No significant difference in productivity was observed under 25 °C and 18 °C. Also, no significant difference in productivity was observed between plants in two temperature settings and plants outside.