Soil pH should be above 6.0. Soil P needs to be only 15 PPM or greater for maximum yield. Don't apply nitrogen to soybeans. Because soybean seed is sold in 50-pound units, buy varieties with small seeds to make a unit plant more acres. Use public certified varieties to control seed input cost.
Public varieties yield well and usually have good resistance to disease.
Buy varieties with proven performance that have been around a couple of years rather than the newer, more expensive ones. If they have not been compared to other varieties in a University performance trial, don't take a chance on them. There were also some very high yielding RR varieties with good disease resistance in the trials. Be very selective if using Roundup Ready varieties. Varieties not entered are usually poorer performers than those entered.