Agronomic response of soybean varieties to plant population in the Guinea Savannas of Nigeria

Summary

The agronomic responses of three contrasting soybean (Glycine max [L.] Merr.) varieties to plant populations were examined in two distinct agro‐ecological locations (at Samaru Zaria and Samaru‐Kataf), both in the Guinea savanna of northern Nigeria in the 2009, 2010, and 2011 growing seasons. Three soybean varieties, TGx1835‐10E, TGx1904‐6F, and TGx1448‐2E, differing in maturity duration (early, medium, and late maturing, respectively), were evaluated at four plant populations (266,700, 333,300, 533,300, and 666,700 plants ha⁻¹) using a split plot arrangement in randomized complete block design with three replications. The plant populations were the main plots, whereas varieties were subplots. The proportion of intercepted photosynthetically active radiation (IPAR) and leaf area index (LAI) increased with increasing plant populations at both locations, indicating that high leaf area indices and a high degree of canopy closure at higher plant population intercept more light than the canopy at lower populations, subsequently resulting in relatively high grain and fodder yields. At both locations, optimum plant populations ranged from 533,300 to 666,700 plants ha⁻¹ across the three years. The northern Guinea savanna location (Samaru Zaria) produced more pods m⁻², grain yield, and fodder at higher plant populations compared to the southern Guinea savanna (Samaru‐Kataf). Varieties TGx1448‐2E and TGx1904‐6F intercepted a higher proportion of IPAR, had higher LAI and produced a greater number of pods m⁻², seeds m⁻², grain yield, and fodder than TGx1835‐10E at both locations in years of good rainfall. These data suggest that soybean yields in the Guinea savanna of northern Nigeria can be increased using higher plant populations than those currently recommended.