벼농사에서 질소유출이 수질에 미치는 영향평가

It is important to understand and evaluate the environmental impacts of rice cultivation for developing environmentally-friendly agriculture because rice is main crop in Korea and rice cultivation have both functions of water pollution and purification with environmental and cultivation conditions. This paper presents the evaluation of nitrogen impact by rice cultivation on water system. A simple protocol was proposed to assess the potential amount of nitrogen outflow from paddy field and most of parameters affect on the nitrogen outflow from paddy field such as the amount of fertilizer application, water balance, the quality and quantity of irrigation water, soil properties, nitrogen turnover in the soil and cultivation method were considered. To develop the protocol, coefficients for parameters affected nitrogen turnover and outflow were gotten and summarized by comparison and analysis of all possible references related, and by additional experiments at field and laboratory. And potential amount of nitrogen input and output by water in paddy field were estimated with the protocol at the conditions of the nitrogen contents of irrigation water, amount of fertilizer application, and irrigation methods. Where irrigation water was clean, below 1.0 mg $L^{-1}$ of nitrogen concentration, rice cultivation polluted nearby watershed. At the conditions of 2.0 mg $L^{-1}$ of nitrogen concentration, 110 kg $ha^{-1}$ of nitrogen fertilizer application and flooding irrigation, rice cultivation had water pollution function, but it had water purification function with intermittent irrigation. At the conditions of 3.0 mg $L^{-1}$ of nitrogen concentration and 110 kg $ha^{-1}$ of nitrogen fertilizer application, rice cultivation had water purification function, but that had water pollution function with 120 kg $ha^{-1}$ of nitrogen application. Where irrigation water was polluted over 6.0 mg $L^{-1}$ of nitrogen, it was evaluated that rice cultivation had water purifying effect, even though the amount of nitrogen application was 120 kg $ha^{-1}$. 벼농사에 의한 질소가 하천수질에 미치는 영향을 종합적으로 평가하기 위해 공급 질소의 유입량과 유출 및 이용되는 양은 동일하다는 질소 balance 개념 평가기법을 개발하였다. 유입량과 유출량 결정에 영향을 주는 시비량, 관개수 수질, 관개량과 물이용 수지, 토양유기물 함량, 토양질소공급량, 유기물 시용여부, 이앙방법, 물관리 방법, 수확량, 암모니아 휘산 및 탈질량, 토양잔류량 등 관련요인들과 요인상호간의 관계를 자료 분석, 현지포장 및 실내실험을 통해 지수화하였으며 사용된 지수들을 종합하여 벼농사의 수질영향평가법으로 제시하였다. 질소의 총 공급량에서 대기유출, 작물이용, 토양 잔류 부분을 제외한 차이를 벼농사에서 질소의 잠재유출량으로 산정하여 벼농사가 수질에 미치는 영향으로 평가하였으며, 개발된 방법으로 평가한 우리나라의 평균적인 환경 및 재배 조건에서 벼농사는 수