循環灌漑を実施する水田流域の窒素・リンの物質収支 [in Japanese] Mass Balances of Nitrogen and Phosphorus in the Paddy Field District Implementing Cyclic Irrigation [in Japanese]
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循環灌漑と従来の灌漑 (逆水灌漑) を実施する琵琶湖沿岸の水田流域において, 窒素とリンの物質収支を調査した. 調査地区では, 循環灌漑は代かき期から中干し前まで, 逆水灌漑は中干し後から落水まで実施された. 調査結果として, 循環灌漑は余剰水とともに窒素とリンの流出負荷を削減することが確認された. 4月末から6月下旬の循環灌漑期では, 用水量のうち約80%が余剰分であったが, 循環灌漑時の地区外への流出はほとんど見られなかった. 循環灌漑時と逆水灌漑時の物質収支の比較から, 循環灌漑は少なくともTNで120gha<SUP>-l</SUP>d<SUP>-1</SUP>, TPで15gha<SUP>-1</SUP>d<SUP>-1</SUP>の流出負荷を削減したことが示された.
Mass balances of nitrogen and phosphorus in the conventional irrigation (Gyaku-sui irrigation; GI) system and the cyclic irrigation (CI) system were investigated in paddy field district close to Lake Biwa, where the CI was mainly run during the period from the puddling season to the start of the mid-summer drainage and the GI was run after the mid-summer drainage. As a result, it was confirmed that the CI system reduced outflow of surplus irrigation water with nitrogen and phosphorus. In the CI period, from the end of April to late June, there was less effluent water from the district even though about 80% of the irrigation water was the surplus water. From the comparison between mass balances in the CI system and GI system, it was shown that the CI system could reduce effluents of TN and TP by 120g ha<SUP>-1</SUP> d<SUP>-1</SUP> and 15g ha<SUP>-1</SUP> d<SUP>-1</SUP> respectively.
- Transactions of The Japanese Society of Irrigation, Drainage and Rural Engineering
Transactions of The Japanese Society of Irrigation, Drainage and Rural Engineering 75(4), 437-443, 2007-08-25
The Japanese Society of Irrigation, Drainage and Rural Engineering