ISHS Acta Horticulturae 797: International Workshop on Greenhouse Environmental Control and Crop Production in Semi-Arid Regions
IMPROVING WATER QUALITY BY USING PLANTS WITH WATER CONVOLVULUS (IPOMOEA AQUATICA FORSK.) AS A MODEL |
| Authors: | Y. Shimoda, M. Takagaki, P. Thongbai, K. Ohyama, K. Ozawa |
| Keywords: | ammonium nitrogen, aquatic vegetable, eutrophication, nitrate nitrogen |
| Abstract:
The ability of plants to improve water quality was examined by using water convolvulus (cv. Ton Pai Bai Yao) plants. A waterway (1 m wide, 50 m long), in which water with approximately 40 mg/L total nitrogen flowed at a rate of 200 L h-1, was used. The waterway was divided into five identical sections in the direction of water flow, and the plants were cultivated at the first, third and fifth sections counted from the inlet. The total nitrogen concentration was 25% lower at the outlet than at the inlet of the waterway; however, nitrate nitrogen (NO3-N) concentrations were not significantly different among the six measuring points, indicating that the plants mainly absorbed ammonium nitrogen (NH4-N) under the present conditions. While water clarity was decreased by rainfall at all the sections due to the inflow of eroded soil, clarity improved with increasing distance from the inlet of the waterway. One possible explanation was that the roots of the plants captured the eroded soil. These results suggest that water convolvulus may be cultivated to improve the water quality in waterways in small islands such as Ishigaki island (24°20’ N, 124°9’ E, 223 km2), where water quality has seriously deteriorated due to eutrophication. | |
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