Tillage, Row Spacing, and Planting Date Effects on Soybean following Corn or Wheat

Abstract

Tillage practices have changed rapidly in recent years to help reduce soil erosion associated with moldboard plowing. The effects of tillage practices on other management decisions in soybean [Glycine max (L.) Merr.] production is unclear. This study was designed to investigate the relationships between tillage, row spacing, and planting date on soybean performance in a corn (Zea mays L.)-soybean rotation at three locations and in a soybean-wheat (Triticum aestivum L.) rotation at one location. Tillage systems evaluated were fall moldboard plow, fall chisel plow, spring disk, ridge-till, till plant (no ridge), and no-till. Soybean was planted in 10- and 30-in. row spacings in early and late May from 1982 through 1985. Percent residue cover after planting ranged from 7 to 15% for moldboard plowing to 74 to 87% for the no-till system. With a few exceptions, little difference was observed in plant density among any of the tillage systems, although plants were slowest to emerge from the no-till system and fastest to emerge from the ridge-till system. Tillage did not consistently affect soybean yield and yield differences were small in most years. The early-planted soybean yield was equal to or higher than that planted later in all but one case. The yield advantage for 10-in. rows compared with 30-in. rows ranged from 8 to 14% when averaged over all tillage systems and both planting dates. Reduced tillage systems had less effect on soybean production than planting date or row spacing.