Quantification of Cooling Effects of Kudzu (Pueraria lobata) Vine Covering on the Thermal Environment of Livestock Buildings.

Heat stress decreases livestock productivity, which will cause high economic losses to the livestock farmers. Kudzu (Pueraria lobata) is an aggressive climbing perennial legume plant, and can be used as high nutritious feed for livestock. The ultimate goal of this study is to cover the walls and roofs of livestock buildings with kudzu, which improves the thermal environment of those during summer seasons, and provides livestock with forage after use. The specific objectives of this study were (1) to confirm the cooling effects of kudzu covering on room air temperature inside the fabricated houses (height 2.6m, width 3.65m, depth 1.83m), and (2) to quantify the two cooling effects; the cooling effect by plant transpiration and that of solar radiation interception by plant screen. Room air temperatures inside the covered (Covered) and non-covered fabricated house (Non-covered), and global solar radiation were continuously monitored. Covering rate and leaf number by plants in 18 frames (0.4m×0.4m each), that were set on the wall and roof, were measured every 2 weeks. To quantify the contribution of each of the two cooling effects, all stems of Covered were cut 5cm above the ground for ceasing plant transpiration at 128 days after transplanting. Estimated average covering rate and leaf number among the 18 frames, and room air temperature differences between Covered and Non-covered showed positively significant relationships. The maximum room air temperature difference was observed to be 3.44℃, when the estimated average covering rate and leaf number were 43.9% and 85, respectively. The contribution of cooling effects by plant transpiration and plant screen was estimated from 6.7 to 13.2 % and from 86.8 to 93.3 %, respectively. We conclude that the kudzu covering is effective for cooling livestock buildings during summer, and the cooling effect by transpiration contributes 6.7 to 13.2% to the overall cooling effects.