Planting configuration x cultivar effects on soybean production in low-yield environments

Texas soybean [Glycine mar (L.) Merr.] growers generally use row spacings ranging from 15 to 102 cm and seeding rates that provide 25 to 62 plants m(-2). However, the interaction of cultivars with planting configuration is not well understood. The objectives of this research were to measure the yield response of selected cultivars to seeding population and row spacing in low-yielding environments and to relate morphology to this response. In north Texas, on a highly calcareous clay soil with 10 maturity group (MG) III cultivars (where 2-yr average yield was 1.22 Mg ha(-1)) and three seeding populations (25-75 m(-1)), only one cultivar, AG3702, showed consistent yield increases at 50 and 75 m(-2). The row-spacing tests were conducted in two north Texas environments where 14 MG IV cultivars varying in leaf size were grown in 36- vs. 71-cm rows and two environments in southeast Texas where 21 cultivars varying in height and maturity (MG IV- MG VIII) were grown (18- vs. 76-cm rows). In north Texas, yields were not significantly different between 71-cm rows (1.3.1 Mg ha(-1)) and 36-cm rows (1.02 Mg ha(-1)). Likewise, in southeast Texas, yield in 18-cm rows (1.49 Mg ha(-1)) was similar to yield in 76-cm rows (1.46 Mg ha(-1)). Cultivar X row spacing effects on yield were not significant and leaf size and plant height did not affect the yield response to row spacing. In general, our results demonstrated that management X genotype interactions within the range of these cultivars and management practices were not important in these low-yielding environments and possibly were overwhelmed by the severity and timing of drought stress.