Relationship between the Movement of Soil Water and Nitrogen in the Volcanic Ash Soil

1998 Fiscal Year Final Research Report Summary

• Project/Area Number: 09660264
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Irrigation, drainage and rural engineering/Rural planning
• Research Institution: Miyazaki University
• Principal Investigator: TOYOMITSU Yukio Miyazaki University, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (70197979)
• Co-Investigator(Kenkyū-buntansha): SUGIMOTO Yasuhiro Miyazaki University, Faculty of Agriculture, Professor, 農学部, 教授 (20041030) ; MUTO Isao Miyazaki University, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (70040863)
• Project Period (FY): 1997 – 1998
• Keywords: Nitrate nitrogen / Soil water / Leaching / Rainfall / Percolation / Hydraulic conductivity / Solute transport

Research Abstract

Potassium nitrate was sprayed over experimental field ( subdivision of 65cm × 150cm ) of the bare field condition in 100gN/mィイD12ィエD1 in order to clarify mutual relationship between movement of soil water and nitrogen, and movement and leaching of the nitrogen were studied from October fifth, 1998 to October fifth, 1999. The soil was collected to 210cm in the auger ( the 20mm diameter ) for the 2 〜 4 week every and every 15cm depth. The quantity of ammonia nitrogen and nitrate nitrogen was obtained by the 10%KCl soil extract. Soil water potential was measured from 30cm to 170cm by the tensiometer in hour by every 20cm depth. And, the volumetric water content was measured to the 90cm depth by the TDR method in 1 hour by every 30cm. Amount of rainfall was recorded throughout the experiment. Results are as follows.
(1) Though the TDR method can not be applied to this experimental field, it is possible to obtain amount of change of soil water, because amount of increase of soil water and amount of rainfall agree almost.
(2) The increase in the soil water is not always shown, and there is a case in which it is the propagation of the pressure only on the increase of pressure potential in the rainfall time.
(3) Zero flux plane in experimental field is located in the vicinity of the 110cm depth.
(4) Most disappears on the rain water in many cases from soil layer to the 90cm depth in a few days, and all most of the rain water disappear after 20th.
(5) The case that amount of rainfall and soil water were less than the case in which there are many amount of rainfall and soil water mainly disappeared more on the transfer of the nitrogen from the soil layer of the 210cm depth. This supposed for the reason that soil water moves macropore mainly when there is much soil water and soil water moves micropore when there is little soil water. It is considered that that is to say, the nitrogen is mainly retained than the macroscopic pore in the micropore.