On Purification Ability of Soil Layr of Paddy Field with Underdrain

1993 Fiscal Year Final Research Report Summary

• Project/Area Number: 04660248
• Research Category: Grant-in-Aid for Scientific Research (C).
• Allocation Type: Single-year Grants
• Research Field: 土木構造
• Research Institution: The University of Tokyo
• Principal Investigator: YAMAJI Eiji The University of Tokyo, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (10143405)
• Co-Investigator(Kenkyū-buntansha): HOSHINO Tatsuo The University of Tokyo, Faculty of Agriculture, Instructor, 農学部, 助手 (40238738) ; YOSHINO Kunihiko The University of Tokyo, Faculty of Agriculture, Instructor, 農学部, 助手 (60182804)
• Project Period (FY): 1992 – 1993
• Keywords: Underdrain / Ammonium / Macropore

Research Abstract

The purpose of this study is to clarify purification ability of soil layr of paddy field using underdrain during rice planting season. So, the method of examination is 1) Field, 2) Pot and 3) Column.
Field examination is the continuous measurement of water volume and quality at the inlet and outlet of the test field with percolation rate of 7mm/day. The quality was analyzed at NO_3^-, NH_4^+, COD, Fe Mn, etc.
The typical result of pot examination with 1/2000a Wagner pot is that 70-99% of T-N and NH_4^+ was removed from irrigation water of 1-10 mg/l at the percolation rate of 2-40 mm/d. And the effect of rice plant was eminent at high contamination.
Column examination was executed with soil column of 5cm diameter, changing density of NH_4^+ and percolation rate. The results of 23 patterns of examination were also diversified. But one equation of specific density with percolation modified pore volume can explain all of the results.
Soil column with macropore can absorb less nitrogen than that without macropore.
From three types of experiments, it was clarified that soil layr can purify contaminated water. To ensure its effect properly, soil and water management is necessary.