화학비료 표준시비량과 시중에서 구입한 퇴비 및 2,000 및 4,000㎏/10a 수준의 처리로 상추를 재배하여 잎 중의 NO3 축적 현상을 비교하였다. 화학비료 표준시비량 처리에 비하여 퇴비 4,000㎏/10a 수준의 처리로 상추의 수량을 충분히 확보하고 잎 중의 NO3 함량을 안전한 수준 이하로 현저히 저감시킬 수 있는 것으로 나타났다. 용탈에 의한 질소의 유실이 거의 없는 온실 조건에서는 상추에 대한 화학비료의 현행 권장 시비수준이 과다한 것으로 판단되며, 상추를 비롯한 야채류의 NO3 함량을 낮추고 토양의 염류집적을 저감하기위해서는 화학비료 적정 시용량에 대한 재검토가 필요할 것으로 판단된다. 안전농산물의 생산을 목표로 하는 유기농업에서도 작물의 적정 질소 요구량을 기준으로 퇴비 등의 질소 공급자재의 시용량을 결정해야 할 것이다.

Accumulation of nitrate in green vegetables is undesirable due to potential risks to human health. Lettuce was cultivated in pots under greenhouse conditions with compost applications of 2,000 and 4,000㎏/10a, and the growth and nitrate accumulation of lettuce were compared with those found in the lettuce cultivated with chemical fertilizers of recommended levels. Contents of NH4-N in the soils of compost applications were much lower than those found in the soil of chemical fertilizer application. Two weeks after lettuce transplant, NH4-N was not found in the soils of compost applications, and in the soils of chemical fertilizers application NH4-N was not found three weeks after lettuce transplant. One week after lettuce transplant, content of NO3-N was much higher in the soils of compost applications, and the contents were rapidly decreased. While, the content of NO3-N in the soil of chemical fertilizers application was rapidly increased due to the nitrification of NH4 released from the applied urea. At the time of harvest, contents of NO3-N in the soils of compost applications were less than 1.4㎎/㎏, but in the soil of chemical fertilizers application the contents of NO3-N was 54.2㎎/㎏. Contents of NH4 in lettuce were about 20㎎/㎏ FW and were not much different among the treatments. However, contents of NO3 in lettuce were significantly different between the treatments of chemical fertilizer and compost. There were significant differences in fresh and dry weights, and growth of lettuce in the compost treatment of 4,000㎏/10a was highest among the treatments. These results indicate that the cultivation with compost only as N source can produce higher yield of lettuce and significantly reduce nitrate accumulation as compared to the conventional cultivation with chemical fertilizers.