抄録
For the last decade the high level yields, 5t-6t/ha, max. 6.5t/ha, of soybean (cv. Okushirome) have been recorded continuosly under the upland conditions converted from rice paddy fields at Saihoku Branch of the Yamagata Prefectural Agricultural Experiment Station, located in Shinjo (38°45'N, 140°18'E). In 1982 and 1983, dry matter accumulation pattern, canopy structure and light penetration for Okushirome under the converted fields at Saihoku Branch were compared with those of some cultivars (Table 2) grown under the fields of Experimental Farm of Hokkaido University (Sapporo, 43°35'N, 141°20'E). Okushirome produced the highest yields in both years, 5.3t/ha in 1982 and 4.6t/ha in 1983. It had also large LAIs (about 6), small light extinction coefficients (K:0.38 and 0.42), long leaf area duration (LAD) and high harvest indices (62% and 56%) compared with those of the cultivars grown in Sapporo (Table 3 and Fig. 5). Grain yield was closely correlated with number of pods (r = 0.886), LAD (r = 0.800) and grain filling period (r = 0.813), regardless of years, locations and cultivars. The K value was related to number of pods per maximum LAI (r = - 0.796), though not related directly to grain yield. As shown in Fig. 6, in 1982 Okushirome showed a peculiar unique plant form that the upper 3 to 4 large leaves on main stem had vertical and long (25 cm to 30 cm) petioles though stem height was very short (Table 2). In addition, leaflets of Okushirome did active solar tracking movements in both years during early morning to late afternoon, suggesting the relation to effective light penetration within the canopies (Fig. 4).
