2001년 국립식량과학원 인공기상실에서 수경재배로 규산의 시용 여부가 영양생장기 벼의 수분과 질소흡수량에 미치는 효과를 조사하여 규산시용 여부 및 공급된 질소의 형태별 처리에 의한 시험품종들의 수분과 질소이용효율을 산출한 결과는 다음과 같다.1. 처리 67일 후의 벼 건물중은 규산처리 시험구 및NH4+NO3 혼합시용 처리구가 규산을 처리하지 않은시험구 및 NH4 단독시용 처리구보다 유의하게 증가하였음.2. 이앙 후 67일간 조사된 벼의 수분흡수량은 규산처리와 규산 무처리 간의 차이가 없었으나 질소흡수량은규산 무처리에 비해 규산처리구에서 유의하게 증가하였음.3. 질소형태별로는 NH4 단독 시용보다 NH4+NO3 혼합시용에서 규산처리 여부와 관계없이 수분과 질소흡수량이 월등히 많았음.4. 수분이용효율은 규산처리 시험구가 규산을 처리하지않은 시험구에 비해 유의하게 증가하였으나 질소형태별 처리에서는 차이가 없었음.5. 질소형태의 혼합처리가 암모늄태 단독처리보다 질소흡수량은 유의하게 많았으나 질소이용효율은 감소하였음.

This study was conducted to evaluate the effect of slow release fertilizers (SRF), crotonylidene diurea (CDU) and latex coated urea (LCU), on nitrogen (N) use efficiency (NUE) and nitrate-N leaching in a silty clay loam soil under polyethylene film mulching (PFM) for sesame cultivation. In PFM plot, concentrations of NO3-N and NH4-N in SRF applied soils were less than that in the urea plot during the whole growing period. However, NO3-N and NH4-N in all the non-mulched plots (NM) were not significantly different. Urea-N in soil treated with SRF was higher than urea plot until 50 days after application and was comparable in all the treatments after 50 days. NO3-N concentrations in leached solution in 21 days after urea fertilization in PFM and NM were 26 mg L-1 and 83 mg L-1 , respectively. However, NO3-N in leached solution at applied CDU and LCU was less than that of urea similar to nitrate concentration in soil. NO3-N in leached solution in applied CDU and LCU in 44 days after application was about 25% lower than that urea plot and PFM, while the NO3-N concentration of CDU and LCU treatment in NM did not changed. Application of SRF increased the yield of sesame and N recovery compared to urea and there was a little difference between SRF and N levels. In conclusion, application of 80% N level with SRF increased N recovery and reduced nitrate leaching without reduction of yields compared with urea application.

This study was conducted to establish the elaborate nitrogen fertilization method to enhance N use efficiency in direct-seeded rice on flooded paddy. The nitrogen uptake by rice plants was insignificant until 25 days after seeding, and increased gradually thereafter. During this early growth stage, rice plants absorbed only the 4~% of basal applied N, while the 45~% of N fertilizer remained in the paddy soil. The absorption of basal N by rice plants was almost completed at 46 days after application. Nitrogen top-dressed at 5-leaf stage was well matched to crop nutrient demand, so it could be absorbed so actively in 8days after application. As a result, we could cut down the amount of N fertilizer to 36~% of the basal N level without significant difference in yield. Plant recoveries of fertilizer 15N applied with different application timings were 7.8~% for basal, 9.4~% for 5-leaf stage, 17.1~% for tillering stage, and 23.4~% for panicle initiation stage, respectively. When urea was applied with nitrogen fertilization practice based on basal incorporation (BN), plant recovery of 15N at harvest was 31.0~% , which was originated from 13.7~% for grain, and 21.3~% of the fertilizer 15N remained in the soil, and the rest could be uncounted. Plant recovery of fertilizer 15N applied with nitrogen fertilization practice based on topdressing at 5-leaf stage (TN), where N rate was reduced by 18~% compared with BN, was 35.1~% (grain 15.6~% ), and 19.9~% of the fertilizer 15N remained in the soil, and the rest could be uncounted. TN showed a higher 15N recovery than BN because it was to apply N fertilizer at a time to well meet the demand of rice plant direct-seeded on flooded paddy. We concluded that TN would be the nitrogen fertilization method to enhance N use efficiency in direct-seeded rice on flooded paddy.