수도재배포장에서 침투수의 Urea-N, NH₄-N 및 NO₃-N의 농도변화

Changes In Concentrations of Urea-N, NH₄-N and NO₃-N in Percolating Water During Rice Growing Season

농경지에 시용되는 질소질 비료의 대부분을 차지하는 요소를 대상으로 수도재배포장에서 요소태(Urea-N)와 암모늄태($NH_4-N$) 및 질산태($NO_3-N$) 질소의 농토를 조사함으로써 논토양에 시용되는 요소비료의 효율 증대 및 환경오염 방지에 기초가 되는 정량적인 자료를 얻고자 요소를 12kg N/10a(관행구)와 24kg N/10a(배비구) 수준으로 시용한 수도재배포장에서 수도재배기간 동안 침투수의 Urec-N, $NH_4-N$ 및 $NO_3-N$의 농도를 porous ceramic cup을 이용하여 토양깊이별로 조사한 결과는 다음과 같다. 관행구와 배비구 모두 전체 시비량의 50%를 기비로 사용한 후 12일이 지난 후에 채취한 침투수에서는 75cm 깊이에서도 Urea-N이 검출되었으며, 그 농도는 관행구 0.06 및 배비구 $0.12{\mu}g/m{\ell}$로서 배비구에서 높았다. 침투수의 $NH_4-N$ 농도는 수도의 영양생장기간 동안에는 변화가 컸지만 출수가 시작된 8월 중순 이후에는 $0.1{\mu}g/m{\ell}$로서 일정하였다. 침투수의 $NO_3-N$ 농도는 관행구 0.1~0.5 및 배비구 $0.2{\sim}0.5{\mu}g/m{\ell}$ 범위로서 요소 시용량간의 차이는 거의 없었다.

This study was conducted to obtain quantitative data on the behavior of surface-applied urea to a paddy field which would help to protect against environmental pollution as well as to increase the efficiency of nitrogen fertilizer. The percolating water samples were collected with porous ceramic cups installed at 25, 50 and 75cm depths in a paddy field during the rice growing season(June 1992-September 1992) and analyzed for urea-N. NHAN and $NO_3-N$. In the paddy field to which urea fertilizer was applied at the rates of 12 and 24kg N/10a, the surface-applied urea was detected even at 75cm depth as the form of urea-N upto 12days after application. The maximum concentrations of urea-N in the percolating water sampled at 25, 50 and 75cm depths were the same irrespective of soil depth and the values were 0.06 and $0.12{\mu}g/m{\ell}$ for the application rates of 12 and 24kg N/10a respectively. The concentrations of $NH_4-N$ gradually decreased with time during the vegetative growth period : thereafter. the concentrations remained nearly constant. The maximum concentrations of $NH_4-N$ at 25cm depth were 1.2 and $5.6{\mu}g/m{\ell}$ for 12 and 24kg N/10a rate respectively. The $NO_3-N$ concentrations of percolating water ranged 0.1~0.5 and $0.2{\sim}0.5{\mu}g/m{\ell}$ for urea application rates of 12 and 24kg N/10a respectively. The nitrate concentration data suggest that nitrification process occurred continuously in paddy field during the rice growing season.