On Purification Ability of Soil Layr of Paddy Field with Underdrain

本研究旨在探讨水稻播种期排水方式对稻田土层的净化能力。因此，检测的方法是1)场，2)锅和3)柱，田间检测是对试验场进出口的水量和水质进行连续测量，渗滤率为7 mm/d。用1/2000a瓦格纳盆栽试验的典型结果是，以2~40 mm/d的渗滤率，1~10 mg/L灌溉水中总氮、氨氮的脱除率为70~99%，在高污染条件下水稻生长效果显著。柱状检验采用直径为5 cm的土柱，改变NH4+浓度和渗滤率。23种检查方式的结果也是多样化的。有大孔土柱比无大孔土柱吸收的氮素较少。通过三种类型的实验，明确了土层对受污染水体的净化作用。为了确保其效果，水土管理是必要的。

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.