Effects of Plant and Row Spacing on Dryland Soybean Yield and Water‐Use Efficiency1

Abstract

AbstractData on effects of plant and row spacing on yield of soybeans [Glycine max (L.) Merr.] have given conflicting results. Most such experiments were conducted under conditions of little or no water stress. The experiments reported here, conducted under more severe stress conditions, broaden the water‐availability spectrum covered. Each spring, 1976 through 1979, soybeans were seeded on Temvik silt loam (fine‐silty, mixed Typic Haploborolls) at Mandan, N.D., in row widths of 15, 45, and 90 cm, and at within‐row spacings of 11, 15, and 23 cm, which resulted in plant populations of 48,000 to 580,000 plants/ha.Soil water depletion by soybeans was generally confined to the upper 90‐cm soil depth. Average (4‐year) water use was 23.6 cm, and was not significantly affected by plant spacing. In 2 of the 4 years, total water use was greatest and average soybean yields were least Prom the 15‐cm row width. Within‐row spacing affected yields in only 1 of the 4 years.Water‐use efficiency was least for 15‐cm rows in 3 of the 4 years. These data suggest that planting in 15‐cm rows enhances water use prior to flowering. In extreme drought situations, this enhanced earlyseason water use leaves less water available for pod‐fill, and seed yields may be reduced accordingly. Under less severe water stress, however, plant and row spacing has no affect on soybean yield.