Thermosyphon performance in turfgrass green season prolongation with shallow geothermal source.

Low temperature stress is an important factor for turf growth in northern hemisphere district with high latitude. In order to prolong turf growing season in winter, thermosyphon temperature units with shallow geothermal source were developed and tested in a water park. The relations between ambient temperature, depth, material, structure, and soil temperature, roots temperature were studied experimentally. The results indicated that both underground soil temperature and roots temperature almost remained constant with hourly ambient temperature. The soil temperature increased with depth. The roots temperature of copper units was higher than that of steel units, and the temperature difference could reach 2°C at most. The roots temperature of structure I units was higher than that of structure II. The impact of material on roots temperature variation became negligible with increasing depth.