Movement of Soil Water and Cattle Urine-N under the Shallow Groundwater Level in the Volcanic Ash Soil

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To know the relationship between agricultural production and water polution, the movement of soil water and nitrate nitrogen in the volcanic ash soil have been researched. The experiment was conducted at the Miyazaki University Farm, Japan. Average rainfall in Miyazaki is 2400 mm per year. The groundwater level lies between 0-350cm depth from the ground surface. The results are as follows ;1. The soil water content just before rain started and the distribution of rainfall influences on the velocity of soil water movement after rain started and the distribution of rainfall influences on the velocity of soil water movement after rain stopped. The reaction time of soil water pressure at 150 cm depth and groundewater level were 5-50 hours from rain started.2. After the application of cattle urine to the experimental plot, the soil water was extracted and analyzed nitrate nitrogen concentrations. Leaching of nitrate nitrogen through soil was from early September to early November. Large quantity of rainfall occurred within this period.3. After the application of cattle urine to the experimental plot, the soil samples were taken and analyzed nitrate nitrogen concetrations. In case of cattle urine applied in summer, leaching of nitrate nitrogen through soil was 38 % of applied nitrate nitrogen in 54 days. In case of cattle urine applied in autumn, leaching of nitrate nitrogen through soil was 47% of applied nitrate nitrogen in 174 days.4. N-labelled cattle urine was applied to small plots in bahiagrass to trace the fate of urine-N in the soil-plant system. After one year, recovery of ^<15>N in measured components was similar for each application date. Between 27-35 % of the applied ^<15>N was recovered in the plant parts with a further 9-12 % remaining in the soil and 1-2 % in litter. Of the ^<15>N applied, 54-60 % was unacounted for in the soilplant system after one year.