Microclimate inside Tunnel-Roof and Jack-Roof tropical greenhouse structures.

摘要

In the tropics, the main constraints of crop production in the open field are extreme solar radiation, high rainfall, insects and diseases. Naturally ventilated tropical crop protection structures were developed to address the constraints. Basically, the structure consists of a simple structural frame, a transparent polyethylene roofing and an insect screen sidewall. This paper presents the comparison between two types of greenhouse structures in terms of in-house microclimate that is very important for plant growth. The environmental parameters involved are air temperature, relative humidity, light intensity, wind speed and carbon dioxide concentration. The naturally ventilated crop protection structures are tunnel-roof and jack-roof at the Malaysian Agricultural Research and Development Institute, Serdang. Tunnel-roof has sidewall open vents, while jack-roof has sidewall and roof open vents as natural ventilators. The average maximum temperature between outside and inside was recorded as 6.57 and 3.35 degrees C for tunnel-roof and jack-roof, respectively. The lowest average relative humidity was recorded as 56.98, 41.10 and 51.13% for the outside structure, inside tunnel-roof structure and inside jack-roof structure, respectively. The difference between two inside structures was 10.03%. The highest value of average wind speed was recorded as 1.39 m second-1 for the outside structure at 14.00 h, while for the inside structure (jack-roof) it was recorded as 0.4 m second-1. The lowest light intensity was recorded at 08.00 h among eleven sessions from 08.00 h to 18.00 h. The average range value of carbon dioxide concentration in the air is 420 to 500 ppm for the inside jack-roof structure and 390 to 490 ppm for the outside structure..