Yield Performance of Shade Tolerant Soybean Cultivars under Shaded Environment at Various Planting Densities

Expanding soybean [Glycine max (L.) Merr.] production under sub-optimum environment faces the problem of production under a shaded environment. The study aimed to evaluate the yield performance of shade-tolerant soybean cultivars under shaded environment conditions at various planting densities and to determine its related traits. A nested design field experiment was conducted at Banjar Sub-district, Pandeglang District, Banten Province Indonesia (lat. 6.37° S, long. 106.11° S) during the dry season from April to July 2019. Two field conditions, under coconut and banana plantation, which were identified as light-shaded (10-20 % shaded) and deep-shaded (40-50 % shaded) were used as main plots. Three soybean cultivars, Dena-1, as identified as shade-tolerant soybean cultivar, Detap-1 and Devon-1 were arranged at each environment with a single row (40 x 20 cm; normal density; 12.5 plants m −2 ) or double row (30 x 20 x 50 cm; high density; 14.5 plants m −2 ). Research results showed that seed yield decreased from 248 g m −2 to 205 g m −2 by the difference of shading. The yield decrease was due to the decrease of total biomass (TDW), branch number, node number, pod number, and seed number, and stomatal density (Nstoma) without any change in harvest index (HI) and guard cell length (Lguard). In plant arrangement, a better seed yield and TDW were resulted from normal density as compared to high density. Under the deep-shaded condition, Dena-1 under normal density (230 g m −2 ) was superior in seed yield but declined significantly when it was grown under high density (161 g m −2 ). Based on the above results, combining shade-tolerant soybean cultivar (Dena-1) and planting density (single row; 12.5 plants m −2 ) is recommended to maintain soybean seed yield under a shaded environment.