農林地からの流出水の硝酸態窒素濃度と土地利用との関係 Relation between Land Use and Nitrate Concentration of Outflow Water from Watersheds of Agricultural and Forest Areas

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Abstract

農林地からの流出水の硝酸態窒素濃度と土地利用の関係を調べるために,北海道の富良野(森林地),釧路(牧草地),根室(牧草地),帯広(畑草地),網走(養豚)の5地区において河川流出水の硝酸態窒素濃度を調査し,その集水域内の土地利用との関係を検討した.その結果,集水域内の畑草地率と硝酸態窒素濃度との間には明確な正の関係があり,その濃度<I>y</I>は畑草地率<I>x</I>(%)の一次式で近似できた.<BR>一方,林地の濃度は低く,0.3mg/<I>l</I>以下であった.また,網走の養豚地帯では糞尿が完全に堆肥液肥化されているので,その流出水濃度は関東地方の養豚地帯に比べて格段に低かった.

The relation between NO<SUB>3</SUB>-N concentration of outflow water and land use in agricultural area was investigated in Hokkaido. Five areas were selected as follows: 1. Furano; forest area, 2. Kushiro; grass land area, 3. Nemuro; grass land area with high cow density, 4. Obihiro; agricultural area including upland field and grassland, 5. Abashiri; large pig farm area.<BR>Nitrate concentrations and flow rates of stream water were measured. In the forest area, the values of NO<SUB>3</SUB>-N concentration were less than 0.3mg/<I>l</I>. In the agricultural area the values were higher than the values found in the forest area. They depend on the percentage of the agricultural land, consisting of upland field and grass land. The concentration of NO<SUB>3</SUB>-N (<I>y</I>) increases with increase in percentage of the agricultural land (<I>x</I>). The estimated regression line was given by the equation <I>y</I>=0.029<I>x</I>. All values of <I>y</I> (mg/<I>l</I>) are included in the range (0.01-0.05) <I>x</I>. The values measured in Kanto districts were higher than that of this investigated area. It was caused by the larger supply of chemical fertilizer and high density of pig farms without an adequate treatment system for fecal matters.

Journal

  • Transactions of The Japanese Society of Irrigation, Drainage and Reclamation Engineering

    Transactions of The Japanese Society of Irrigation, Drainage and Reclamation Engineering 1995(178), 529-535,a3, 1995

    The Japanese Society of Irrigation, Drainage and Rural Engineering

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