Four experiments were conducted at four locations in Arkansas during 1997, 1998, 2002, and 2003 under early-, full-season-, and double-crop soybean production systems to determine whether ultra-low or high plant populations, planting date, irrigation, row spacing, and genotype selection would affect yield, agronomic characteristics, and seed quality traits.; In 1997 and 1998, under a full-season soybean production systems with ultra-low plant populations, irrigation significantly increased plant height, pod setting, yield, and seed germination. Seed yield from 0.5m row spacing was generally higher than that from 1.0m row spacing. Competitive yields were obtained for plant populations as low as 40,000 plants ha-1.; In 2002 and 2003, under three soybean production systems with high plant populations, planting date, irrigation, and genotypes significantly affected yield, plant height, and maturity. The irrigation contribution to yield was the highest among independent variables. The genotypes contributed significantly to variations in plant height, maturity, and number of nodes, branches, pods, and seeds plant-1. May planting achieved the highest yield followed by April planting and then by June planting. Irrigation significantly increased plant height and prolonged the growth period. Planting dates, irrigation, and genotype selection also had significant impact on the number of nodes, pods, seeds plant-1, and seed size.; Late-maturing genotypes were taller with more nodes and seeds plant -1 than early-maturing genotypes. However, the number of branches plant-1 appeared to be stable among genotypes under different treatments. Row spacing did not show significant impact on seed yield, maturity, and plant height. Late-maturing genotypes were more responsive to irrigation for yield and plant height. Plant height remained similar between May- and June-planting under dryland conditions, but increased significantly with June-planting under irrigation.; Planting date, irrigation, and genotypes significantly affected seed quality traits. Irrigation significantly affected seed viability and vigor, protein and oil content, and seed infections. The maturity group and genotype selection had the highest contribution to protein content, oil content, and seed visual quality ratings. Significant improvement in standard and cold germination was observed as planting was delayed from April to June. Genotype selection is effective for all production systems in achieving high seed yield and quality.
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