THE EFFECT OF INORGANIC NITROGEN AT IRRIGATION TERMS IN TONE RIVER

Abstract

 In this study, we investigated the effect of the concentrations of inorganic nitrogen from paddy field effluent water on the Tone River in Gunma Prefecture. The concentrations of inorganic nitrogen of the Tone River were 1.0-3.0mg/l from May to August. On the other hand, the values increased from August. We investigated the concentrations of inorganic nitrogen in inflows and outflows from a paddy field in Takasaki city. The outflows values were low compared with inflows. These results suggest that the Tone River water is influenced by paddy fields. I calculated that the amount of nitrogen removal was about 19.4 mg/m²/day in August and 6.7 mg/m²/day in September. I estimated the nitrogen removal in planted paddy fields. The amount of nitrogen removal is about 0.06-0.48% at the Toneoozeki, down stream point of Tone River in Gunma Prefecture.