Behavior of Nitrogen Released from Chinese Milk Vetch in Paddy Soil by Using Stable 15N Trace

Green manure cultivation affects soil productivity and nutrient conservation in paddy soil at winter season. This study was to evaluate nitrogen behavior released from chinese milk vetch (CMV) as green manure by using stable $^{15}N$ trace during rice cultivation. The CMV used in the experiment was 29.9 of C/N ratio and 14.1 g N $kg^{-1}$ ($^{15}N$ 0.388 atom % excess) and was applied at rates of 10 and $30Mg\;ha^{-1}$ in pot of 1/2000a size. Rice growth and N uptake increased with higher levels of CMV application at harvesting stage. Among total N uptake, 14.6 and 26.8 % of nitrogen was released respectively from the two different rates of CMV application. Stable $^{15}N$ recovery by rice biomass was 60%, 54% to the $^{15}N$ input, respectively, of CMV application, which decreased in order of grain, root, and straw of rice biomass. Total N content in the soil after rice harvest was 1.9 and 2.1 g N $kg^{-1}$, respectively, with increasing N input by the different rates of CMV application and the rate of $^{15}N$ recovery derived from CMV in the soil was 3.8 and 4.8 %, respectively. N input by CMV application induced rice growth and productivity during rice cultivation. However, it might need proper managements to reduce N loss because about 36-41 % of nitrogen was lost from N input by CMV application.

논토양 중 자운영 환원에 의한 질소의 동태 구명

담수조건으로 토양질소동태에 대한 결실기 자운영의 투입효과를 포트시험을 통해 평가하였다. 자운영의 투입에 따라 벼의 자운영유래 질소 이용율은 약 51-64%으로 자운영의 투입량이 높을수록 감소하였다. 수확기 토양의 자운영질소는 약 3-5%가 저장되었고, 자운영 유래 질소의 손실은 각각 32.4와 44.1%를 차지하였다. 벼 수량 대비 자운영 $30Mg\;ha^{-1}$ 시용은 질소추천시비량을 전량 대체할 수 있었다.