Underground water contamination and movements of nutrients in soil under sand dune cultivation

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The research was carried out to clear the actual condition of groundwater contamination with nitrate and the movement of nitrate in soil under sand dune cultivation.Nitrate concentration of groundwater underfarmlands around Tottori sand dune has been monitored every month form August, 1993. This year, Hojo and Yumigahama sand dune , which are located at central and western part of Tottori prefecture respectively, were added as monitoring site.High concentration of NO_3 in the range of 10-40 mg N/L, was always observed in the western area of Tottori sand dune (Karo district), where was the area of flower and vegetable production, while in the eastern area (Yuyama district), where was the area of bakers garlic production, mostly the concentration was less than 10 mgN/L.It seemed that high NO_3 concentration in the Karo district resulted form heavy application of fertilizer and penetration of waste water discharged from hencoop into soil. In the area of Hojo sand dune, where was the area of chinese yam and grape production with heavy application of fertilize , most of groundwater was polluted with nitrate and the concentration of was in the range of 10-20 mgN/L.In the area of Yumigahama sand dune, where was the area of leek production, mostly the concentration of NO_<3->N was less than 10 mgN/L.As a result of the column experiment on various irrigation conditions by using sand dune soil, it was clarified that the amount of NO_3 leached by irrigation increased in proportion to the volume of irrigation water.It was predicted that the contamination of underground water with nitrate became a more serious situation if the current soil management was continued on the sand dune farmland.