Date of Planting and Row Spacing Effects on Four Soybean Cultivars1

Abstract

AbstractSoil moisture conditions favor April planting of soybeans [Glycine may (L.) Merr.] in the southern USA, but reports have indicated that soybean cultivars were not adapted to April planting. Data are not available on the response of newer cultivars to early and late plantings. Also, reports from the north central USA have indicated that soybeans yield more when planted in narrow (46 cm or less) than in wide (92 cm or greater) rows, but there are conflicting data regarding row width from the southern USA.A 3‐year study was conducted on a Tifton silt loam (fine‐loamy, siliceous, thermic, Plinthic Paleudult) at Tifton, Georgia (31° 28‘ N). ‘Essex’, ‘Davis’, ‘Bragg’, and ‘Hutton’, maturity groups V through VIII, respectively, were planted in narrow (46 cm) and wide (92 cm) rows at 15day intervals from early April to early July.The interval from planting to flowering decreased for Essex and Davis as the planting date was delayed from early April through early July. This relationship occurred for Bragg and Hutton after early May planting. Essex was the earliest flowering and produced the shortest plants among all cultivars within each planting date. Essex was too short for efficient combining.The overall effect of narrow rows vs. wide rows was a yield inuease of 1.2 quintals/ha or 4.2%, but yield response to narrow row planting was not affected by cultivars or planting dates.Highest yields of Essex were obtained from early May planting. The other three cultivars yielded equally well when planted from late April through early June. Yields of all cultivars were lower for early April and early July plantings than for May and early June plantings.May to early June was the optimum planting period for Davis, Bragg, and Hutton for the combined factors of yield, plant height, and seed quality, and none of the cultivars performed well in April planting. However, the late flowering characteristics of Davis, which apparently is responsible for relatively tall plants in April plantings, offers possibilities for use in breeding programs to develop desirable cultivars for April plantings but improved seed quality needs to be combined with other desirable traits.