Influence of Heating Pipe Placement on Microclimate of Greenhouses with Raised-Trough Tomato Production System

The influence of heating pipe placement (HPP) on microclimate of greenhouses using raised-trough cultivation system was investigated based on overnight and monthly-overnight data. The experiment was conducted in greenhouses that equipped with two different HPP methods with a tomato crop. The HPP consisted of: 1) conventional: hot-water (20-80 °C) pipe (0.051m) loop was installed horizontally at 0.10m above the ground and between two raised-troughs hanged at 85 cm high, 2) new: hot-water pipe (0.051m) loop was placed horizontally at 0.40m underneath the raised-troughs, and a first stage heating pipe (0.021m) was also installed inside at the center of a double row crop canopy and 0.55 m above the top surface of the raisedtrough. The mean air and leaf temperatures at different heights along the crop canopy were higher (about 0.7-1 °C) with new than that of conventional method. However, above canopy air temperatures were almost similar ( ± 0.2 °C) for both conventional and new HPP methods. Thus, a higher leaf temperature was achieved along the crop using new HPP even with similar above canopy air temperatures. Higher stem temperature (about 1 °C) was observed with new HPP method. Top stem temperature was always lower (about 0.5 °C) than bottom one in the conventional HPP method, whereas bottom and top stem temperature with the new HPP method was similar for all months. Observed higher air, leaf, and stem temperature with new heating method might be beneficial for early plant growth and development.