Nodulation, dry matter accumulation and yields of soybean (glycine max L.) cultivars at varying plant spacing in a rainforest agro-ecology

Field trials were conducted during 2017 and 2018 late cropping seasons at the Teaching and Research Farm of the Faculty of Agriculture, University of Benin, in the rainforest zone of Nigeria to evaluate soybean (Glycine max L. Merrill) cultivars for nodulation, dry matter accumulation and seed and fodder yields at varying plant spacings. The trial was laid out in a randomized complete block design with split-plot arrangement replicated four times. Four plant spacings (50 × 30 cm, 60 × 25 cm, 75 × 20 cm, and 100 × 15 cm) were evaluated on six soybean cultivars: TGX1835-10E and TGX1987-62F (early maturing), TGX1951-3F and TGX1955-4F (medium maturing) and TGX1448-2E and TGX1904-6F (late maturing). Results showed that varietal performance depended on plant spacing. TGX1904-6F nodulated best at plant spacing of 50 × 30 cm, TGX1835-10E at 60 × 25 cm, TGX1987-62F at 75 × 20 cm, TGX1448-2E at 75 × 20 cm, and TGX1951-3 at 100 × 15 cm. TGX1835-10E accumulated dry matter most at plant spacing of 60 × 25 cm and 75 × 20 cm, TGX1987-62 at 75 × 20 cm, TGX1951-3F at 60 × 25 cm, TGX1955-4F at 60 × 25 cm and 75 × 20 cm, TGX1904-6F at 50 × 30 cm, and TGX1448-2E at 60 × 25 cm and 75 × 20 cm. TGX1448-2E and TGX1904-6F had higher seed and fodder yields at plant spacing of 50 × 30 cm, TGX1951-3F and TGX1955-4F at 60 × 25 cm, and TGX1835-10E and TGX1987-62F at 75 × 20 cm, relative to other plant spacing. Therefore, for higher yields in rainforest agro-ecology, farmers should adopt the right cultivar-plant spacing combination for soybean.