초록
미사식양토에서 질소로 $240kg\;ha^{-1}$에 상당하는 생헤어리뱃치와 화학비료 초안(질산암모늄)을 옥수수 파종 1주일 전에 토양에 혼입하고 옥수수를 재배하면서 토양 무기태질소, 미생물태질소, 옥수수 지상부의 질소 집적량을 1997년부터 2년간 조사하였다. 헤어리벳치의 초기분해 시 초안 유래의 질산태질소의 60-70%에 달하는 질소량이 헤어리뱃치로부터 무기화되어 토층 0-15 cm에 집적되었다. 또한 토양미생물태 질소도 헤어리뱃치구가 초안구보다 $10-20mg\;kg^{-1}$ 증가하였으며 약간의 헤어리뱃치 유래 토양무기태 질소는 천천히 무기화되어 출사기 이후까지 옥수수에 공급되는 것으로 보였다. 출사기에서의 옥수수의 전체 질소 집적량은 2년간 모두 두 질소원 간에 차이가 없었다. 옥수수 수확기의 질소 집적량은 1997년도에는 헤어리뱃치 녹비구가 초안구보다 8% 적었지만 1998년도는 오히려 19% 증가하였다. 질소원으로서 $240kg\;N\;ha^{-1}$에 달하는 헤어리벳치녹비의 시용은 완효적인 질소무기화 효과를 나타내었으며 같은 량의 질소 화학비료를 대체할 수 있는 옥수수 생육촉진 효과를 보였다.
Fresh hairy vetch (HV) as a green manure equivalent to $240kg\;N\;ha^{-1}$ were incorporated into soil at corn planting in 1997 and 1998 to clarify the effects on changes of nitrogen (N) content in soil and corn plant. The influences of HV for the N of soil and plant were compared with those of ammonium nitrate (AN) in terms of mineralization and microbial biomass. During early decomposition of HV residue, the content of $NO_3-N$ in HV plot was as much as 60-70% of that in AN plot in surface soil of 0-15 cm depth. In addition, soil microbial biomass N (SMBN) by HV residue was increased up to $10-20mg\;kg^{-1}$ more than that by AN. Some mineral N from HV seemed to be released slowly until late corn growth stage judging from high content of $NO_3-N$ in both corn stem at silking stage and soil at harvest. There were no difference of N accumulations in corn plant at silking stage between HV and AN plots in both 1997 and 1998. At harvesting stage, a total of plant N accumulation in HV plot in 1997 was 8% less than that in AN plot while in 1998 it was 19% more. It was concluded that fresh HV green manure equivalent to $240kg\;N\;ha^{-1}$ was good enough to substitute the same amount with chemical N fertilizer by slow releasing of mineral N from HV residue in soil.
