**2.2 Growth and yield observation**

Thirty plants were harvested from each plots, and ten standard plants were selected to examine the node number, main stem length, stem diameter, stem weight, and seed/stem weight ratio. Pods were distinguished on the position, main stem/branches and raceme order (Fig. 1.), and seeds were depodded manually, then weighed to record the data on yield and yield components.

The raceme orders were defined as follows (Torigoe et al. 1982). The terminal racemes appeared at the top of the stems, and first order racemes differentiate from the axil just above the petiole on the stem. The secondary racemes differentiate from both sides of the first order raceme and tertiary racemes differentiate from the sides of the secondary racemes. Racemes differentiating from both sides of the branch were classified as secondary racemes. The terminal and first order racemes, and those over secondary raceme will be collectively called basal raceme and lateral raceme, respectively. Some lateral racemes had compound leaves. The lodging score was recorded every week by measuring the angle of the main stem, and ranked 0 (erect), 1 (inclined 15 degrees), 2 (inclined 45 degrees), 3 (inclined 75 degrees) and 4 (inclined horizontally), then the average score was obtained.

Fig. 1. Classification of raceme order in determinate type of soybean.

#### **2.3 Dry matter production and canopy structure**

Five plants (three replication for each plots) were sampled and three (nine plants for each plots) were separated into leaves, petioles, stems and pods on each main stem and branch, then measured the leaf area of a standard plant (AAM-8, Hayashidenko). Samples were airdried at 80 degrees C for 48 hours and weighed. At the beginning of flowering and full seed growth stage relative PAR (photosynthetically active radiation) at each height of the canopy were measured with a long PAR sensor (LI-191S, LI-COR) in the evening under diffuse light condition. Then, canopy structures were surveyed by the stratified clip method (Monsi und Saeki 1953). From the logarithmic relationships between cumulative LAI of the canopy top and relative PAR, the canopy light extinction coefficient (k) was obtained. In addition, the relative PAR at the height of 0, 60 and 120cm above the ground was measured every 2.5 hours from 7 a.m. to 17 p.m., and diurnal change in light extinction coefficient under direct light condition was obtained.

#### **2.4 Cumulative solar radiation within canopy**

Integrated solarimeter films (R-2D, Taisei E&L) were used for the measurement of cumulative solar radiation. Film was cut in 1cm width and 2cm length, then placed at 10cm intervals on the square bars, 1cm width and 100cm length, which were installed horizontally every 15cm height from the soil surface. The dye percentages were measured every six hours by a spectro-photometer (UV-1200, Shimadzu). The dye percentages had been calibrated with the cumulated solar radiation measured by radiation sensor (LI-200SA, LI-COR). Accordingly, the distribution of solar radiation within a canopy was calculated.

### **2.5 Weed emergence**

Three quadrats (80cm\*60cm) were randomly arranged within each plots. At the beginning of flowering stage, all weeds were sampled and the number and dry-weight of each weed species were recorded.
