[A-GE28] Subsurface Mass Transport and Environmental Assessment

[AGE28-P05] Evaluation of natural latex application for reducing soil runoff by using Ishigaki soil

*Koki Kumamoto¹, Hiroaki Somura¹, Toshitsugu Moroizumi¹, Yasushi Mori¹, Jun Kano¹, Mamoru Matsushima², Nantina Moonprasith³ (1.Graduate School of Environmental, Life, Natural Science and Technology, Okayama University, 2.Kyokuto Rubber CO., LTD, 3.National Metal and Materials Technology Center, Thailand)

Keywords:Environmental conservation, Small scale rainfall simulator , Ishigaki agricultural soil, Soil runoff

Soil runoff from agricultural land due to heavy short-term rainfall has become a problem in tropical and subtropical regions. It is also observed in Ishigaki Island, causing coral death by inhibiting photosynthesis. Our previous studies have shown that mixing natural latex with agricultural soils collected in Thailand can promote soil particle aggregation and reduce soil runoff. The purpose of this study is to evaluate the ability of natural latex for Ishigaki soil by conducting a two-hour artificial rainfall experiment using a small, self-made rainfall simulator. Two rainfall intensities (20 mm/h, 50 mm/h), three latex mixing concentrations (0%, 0.05%, and 0.1% of soil mass), and two soil slope conditions (5°and 10°) were set in the experiments. To determine the persistence of the latex effect, the experiment was repeated under the same conditions 24 hours after the experiment. The experiments were also conducted three times each. No surface runoff was observed under all conditions of slopes and latex admixture amounts at a rainfall intensity of 20 mm/h. The infiltration flow increased as the latex admixture amount increased, and decreased as the slope became steeper. On the other hand, at a rainfall intensity of 50 mm/h, surface runoff was observed. The higher the latex admixture amount, the more surface runoff was suppressed and infiltration runoff was increased. Similarly, the smaller the slope, the less surface runoff and the more infiltration runoff occurred. These results confirmed that latex had the potential to reduce soil runoff even under high rainfall intensity. In order to apply latex in real agricultural fields, we need to look into the persistence of natural latex effect, the appropriate amount of admixture, and the proper method for incorporating latex to the soil.