Optimizing Soybean (Glycine max L.) Yield Through Planting Density Management in Togo

Soybean is a major legume crop in Togo. However, there is no scientific basis for guiding planting density recommendations to enhance yield. This study evaluated six soybean varieties across multiple planting densities in two major soybean-growing areas of Togo over two years. Data were collected on morphological traits and yield and were subjected to variance analysis, heritability estimate and mean comparison using R software version 4.4.1. Heritability was high (>0.8) for most traits except for number of branches per plant (0.54) and pod weight per plant (0.50). The local check variety (TGX1910) consistently outperformed introduced lines at all planting densities, except for hundred-seed weight. Plant height increased with density, whereas branch number, pods per plant, and grains per plant decreased, reflecting soybean’s self-regulation. Grain yield ranged from 1.17 t/ha at 200,000 plants/ha to 3.83 t/ha at 333,000 plants/ha. Despite reduced individual plant productivity at higher densities, plot yield increased up to an optimal density of ~333,000 plants/ha, before declining at the highest density of 450,000 plants/ha. Wider row spacing (60 cm) slightly enhanced yield compared to narrower spacing (40 cm). These results demonstrate that optimal planting density maximizes population-level yield, and planting soybean at 333,000 plants/ha with 60 cm row spacing is recommended for Togo.