Abstract
To improve the existing nitrogen recommendation method based on chemical properties of soils and to establish new recommendation rates of nitrogen fertilizer due to different types of soils, the application rates of nitrogen fertilizer were examined in different soils of 12 experimental rice paddy fields. The application rates of nitrogen fertilizer estimated by soil-testing were higher than the rates of nitrogen standard recommendation that has been used. The application rates for minimum rice productivity ranged from a low of 168 kg/10a in sandy soil to a high of 315 kg/10a in saline soil. Amounts of nitrogen absorption in rice were proportional to the application amounts of nitrogen fertilizer in soils. Nitrogen use efficiency was the highest, 36.7%, in immatured paddy field and it was inversely proportional to the application amounts of nitrogen. the rice tasty value was the highest in the soils without nitrogen application, and also it was the lowest in the saline soils with or without nitrogen application. As comparing with the nitrogen application rates obtained by the existing nitrogen recommendation method, optimal nitrogen application rates estimated by the standardization of nitrogen application efficiency rate, environmental index, and rice quality were 1.0 fold in the well adapted soil and sandy soil fields, 0.92 fold in the immatured soil field, and 0.83 fold in the saline soil field.
토양화학성을 고려한 기존의 토양검정 시비추천방법을 보완하기 워하여 논토양 유형별 질소시비기준을 설정하기 위하여 12개 벼 시험포장에서 토양유형별 질소검정시비량 시험을 실시하였다. 유형별 토양검정에 의한 질소시용량은 질소표준권장량 보다 많게 환산되었고, 질소수준별 회귀분석에 의한 최소 수량 생산시비량은 염해답에서 315 kg/10a, 사질답에서 168kg/10a로 최고와 최저시비량을 보였다. 유형별 질소흡수량은 질소시비량과 비례관계였고, 질소이용률은 미숙답에서 36.7%로 가장 높았으며, 질소시비량과 반비례 관계였다. 쌀의 식미치는 논토양 유형에 관계없이 무질소에서 높았고, 유형별로는 염해답에서 가장 낮았다. 시비효율지수와 환경지수 및 쌀 품질을 표준화하여 얻은 최적시비량은 보통답과 사질답에서는 토양검정 시비량의 1.0배, 미숙답과 염해답에서는 각각 0.92와 0.83배 했을 때 최적 시비량 수준을 보였다.
