Abstract
This experiment was carried out to investigate the optimum planting density in low fertilizing cultivation of machine transplanting in rice field of Honam Agricultural Research Institute, NICS for $2004{\sim}2005$. Sobibyeo which belongs to medium maturing variety and Nampyeongbyeo which belongs to medium-late maturing variety were transplanted on May 30. In this experiment, there was no significant difference in heading date between planting density and nitrogen fertilization rate, and heading dates were August 8 in Sobibyeo, and August 14 in Nampyeongbyeo respectively. In relation to lodging character, lodging Index was high where the nitrogen fertilization rate and planting density were high. As planting density increases, panicle number per $m^{2}$ increased irrespective of nitrogen fertilization rate. When nitrogen was 6 kg/10a, rice yield of Sobibyeo was more where planting density was 90 hill per $3.3m^{2}$, and that of Nampyeongbyeo was more where planting density was 80 hill per $3.3m^{2}$. When nitrogen was 9 kg/10a, rice yield of Sobibyeo was more where planting density was 100 hill per $3.3m^{2}$, and that of Nampyeongbyeo was more where planting density was 110 hill per $3.3m^{2}$. Head rice rate of brown rice was higher when planting density increased, and was higher at 6 kg/10a nitrogen rate than 9 kg/10a nitrogen rate in all varieties.
가. 재식밀도가 높을수록 주당 경수는 적었으나 단위면적 당 경수는 많았으며, 엽면적지수가 높았고, 지상부건물중도 무거웠다. 나. 재식밀도와 질소시비량간에는 출수기 차이는 없었고, 품종간에는 소비벼는 8월 8일, 남평벼는 8월 14일이었다. 다. 도복관련 형질은 질소시비량이 많고 재식밀도가 높을수록 도복지수가 높았으며, 절간장은 질소시비량이 많을수록 컸으며 품종간에는 소비벼가 $1{\sim}3$절간은 컸으며 $4{\sim}5$절간은 남평벼가 컸고 그 차이는 N9 kg/10a 시용구에서 더컸다. 라. $m^{2}$당 수수는 시비량에 관계없이 재식밀도가 높을수록 많은 경향이었으며, 쌀수량은 6 kg/10a의 질소 수준에서는 소비벼는 90주, 남평벼는 80주가 많았으며, 9 kg10a 질소수준에서는 소비벼는 100주, 남평벼는 110주에서 많았다. 마. 현미의 완전미 비율은 재식밀도가 낮을수록 높았으며, 질소시비량간에는 두품종 모두 6 kg/10a 시용구가 9kg/10a 시용구보다 높았다.
