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

为了了解农业生产与水污染之间的关系，研究了火山灰土中土壤水分和硝酸盐氮的运动。该实验在日本宫崎大学农场进行。宫崎县的年平均降雨量为2400毫米。地下水位位于距地表0-350cm深度之间。研究结果如下：降雨前土壤含水量和降雨分布对降雨后土壤水分运动速度的影响，降雨分布对降雨停止后土壤水分运动速度的影响。150 cm深度土壤水压与地下水位的反应时间为降雨开始后5 ~ 50 h。试验小区施用牛尿后，提取土壤水分，分析硝态氮浓度。硝态氮通过土壤淋滤的时间为9月初至11月初。在这段时间内发生了大量的降雨。试验小区施用牛尿后，采集土壤样品，分析硝态氮浓度。夏季施用牛尿时，54 d土壤硝态氮的淋失量为施用硝态氮的38%。在秋季施用牛尿时，174天土壤硝态氮的淋失量占施用硝态氮的47%。在百喜草小块地施用n标记牛尿，以追踪尿n在土壤-植物系统中的去向。一年后，在每个应用日期，测量组分的采收率都是相似的。施用氮的27- 35%在植株部分被回收，另有9- 12%留在土壤中，1- 2%留在凋落物中。在施用的N <15>中，54- 60%的N在一年后在土壤系统中消失。

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.