Growth and Yield Responses of Soybean to Planting Density in Late Planting

1. 남부지역에서 대원콩을 이용하여 재배한 결과, 주당본수를 높일수록 식물체 간 경합에 의해 경장은 길어지고 경태는 가늘어지며 분지수가 감소하여 도복에 취약한 초형으로 생육한다. 다만 만파재배 시에는 생육기간이 단축되므로 주당본수를 높이더라도 도복이 우려될 만큼 경장이 신장하지 않는다. 2. 마디수는 주당본수 별로 유의한 차이가 나지 않았으며 협수는 주당본수가 높아질수록 감소하는 경향을 나타내었다. 3. 재식밀도의 증가에 의한 증수효과는 7월 중순이후로 극만파할 때에 관찰되며 1주 4본 재배 시 표준재배에 비하여 34 % 증수효과가 있었고, 1주 5본 이상 재배할 경우 오히려 수량이 감소하였다. 4. 따라서 만파재배 시에는 밀식하여도 잘 도복하지 않으며 $70{\times}20cm$ 로 재배할 때 1주 4본까지 재식밀도를 높이는 것이 수량증대에 유리하다. Soybean is one of the important food crop around the world. Especially in East Asia, it is the main ingredient for traditional food like soy sauce and soy paste. The double cropping system including soybean following onion, Chinese cabbage, and potato is widely adopted in Southern region of Korea. In this system, sowing date of second crop (soybean) can be delayed depending on first crops' growth period and weather condition. When planting date is delayed it is known that soybean yield is declined because of shorter vegetative growth period and earlier flowering induced by warm temperature and changes in photoperiod. The objective of this study was to determine soybean growth and yield responses as plant populations at late planting date. Field experiment was conducted at Department of Functional Crop, National Institute of Crop Science, RDA located in Miryang, Gyeongsangnam-Do for two years ('13-'14) in upland field with mid-late maturity cultivar Daewon. A split-plot block design was used with three replications. Main plots were three sowing dates from June 20 to July 20 with 15 days intervals, and subplots were 4 levels of planting densities. Data of maturity (R8) was recorded, yield components and yield were examined after harvesting. Experimental data were analyzed by using PROC GLM, and DMRT were used for mean comparison. Optimum planting population for maximizing soybean yield in late planting which compared with standard population. In mid-June planting, higher planting density causes increased plant height and decreased diameter which lead to higher risk of lodging, however, reduced growth period due to late planting alleviated this problem. Therefore higher seeding rates can provide protection against low seedling emergence caused by late planting in this region.