Soybeans
What is the optimum row spacing for soybeans?
Soybean varieties adapted to Mississippi can produce high yields over a wide range of row spacings and plant populations. If you use timely planting and superior varieties, there is no research evidence in Mississippi that shows an advantage for any row spacing (of 30 inches or less). Generally, row spacings less than 30 inches will yield more than 38 to 40 inch rows (10 to 15 percent more), and varieties grown today are much more adapted for narrow rows.
Eighty percent of Mississippi's soybean crop is grown on heavy clay soils, a situation where planters often perform a much better job of seed placement and coverage as do drills. Currently, there are a few drills that have been introduced that do a much better job of seed placement. Although placement has been improved, seed metering is still less than desirable.
A recent planting date study was conducted in Mississippi at three locations (Stoneville, Macon, and Verona) evaluating three row spacings (10, 20, and 30 inch rows) over different planting dates ranging from early April to mid-July. This study showed no difference in row spacings.
Twelve popular varieties ranging from early Group IVs to Group VIs planted over a 3 year period showed no difference. The major factors contributing to increased yields were variety selection and planting date. Both of these inputs were much more important than row spacing. There are years and situations where drilled beans may outperform wider rows, but this should be a management decision for each individual operation.
Narrow rows (7 to 10 inches) will really try your weed management skills, but statewide the bulk of the crops is planted in 15 to 20 inch rows with a planter type unit.
As planting dates are delayed (late May or later) you need to use narrow rows. More narrow is best. In determining row spacing, attempt to match varieties to row spacing. The overall objective is to have a complete canopy formed by the onset of bloom.
For additional information, see Mississippi State University Extension Service Publication 1194, Soybeans: Plant Populations and Seeding Rates and Publication 1289 Soybean Planting Guidelines.
