Irrigation, Row Width, and Plant Population in Relation to Growth Characteristics of Two Soybean Varieties 1

Soybean ( Glycine max (L.) Merrill) yields in the past have varied considerably from year to year in the southeastern United States. Many factors are important in soybean production, but water stress at critical growth periods appears to be one of the most frequently limiting factors. Soybeans were grown on a Lucedale fine sandy loam soil to determine the effects of three soil water regimes at two row widths and three plant population levels on water use, rate of plant growth, and bean yield of two varieties. Water use rates by soybeans were influenced more by soil water regime than by row width or variety. Average rates during the season ranged from 0.05 to 0.84 cm/day, depending on the amount of available water in the soil. Variety had the greatest influence on plant height. Final plant heights ranged from 10 to 15 cm greater for ‘Bragg’ than for ‘Hampton 266.’ Heights were increased by irrigation and plant population level, but were not affected by row width. Average bean yields were influenced more by irrigation or variety than by row width or plant population. Average bean yields by soil water regimes were 2,020, 2,420, and 2,490 kg/ha for no irrigation, intermediate, and high irrigation, respectively. Bragg averaged 2,420 kg/ha and Hampton 266 averaged 2,150 kg/ha. Row width and plant population showed little influence on average bean yields.