The soybean plant typically requires planting in heavier soils, but tolerates a variety of soil types. However, wet, poorly-drained soil often makes the plant more susceptible to disease; it should be grown in a well-drained area to maximize potential yield. The soybean plant can also withstand some stress from drought.
The soybean plant requires more moisture for germination than crops like corn, so planting of the seed should ensure sufficient contact between the seed and dirt to allow for proper transfer of moisture from the earth to the seed. The University of Missouri Extension service indicates the seed should never be planted deeper than 2.5 inches.
The best yield is available to the plant when soybean seeds are entrenched no more than one to 1.5 inches into the ground. If planted early, seeds should be placed shallow; if planted late, placed deeper. The density of surrounding soil also plays a part--plant seeds shallow if the soil is heavy, and vice-versa.