Drought
If conditions are too dry, leaves wilt and plants have reduced growth. Droughty conditions reduce yields by increasing flower and pod abortion and reducing seed number and size.
Flooding
Extended flooding may cause plants to be stunted and yellow. Flooding during early vegetative growth stages (V1-V2) and early reproductive stages (R1-R3) may have the greatest impact on yield.
Frost Damage
Soybean plants may be damaged if air temperatures drop below 27-28°F. If frost injury occurs early in the season, replanting may be required. Sometimes only upper leaves, but not the growing points, are damaged and growth will resume from surviving buds. A late season “killing frost” can reduce yields by reducing seed size and/or resulting in harvest of immature (green) seed. Plants appear wilted and, if completely frozen, leaflets die, drop off and plants die.
Green Stem
Green stem is when stems remain green and moist at maturity. Leaves may or may not remain attached to the stem. This can result in reduced yields and lower seed quality. Virus infections have been associated with green stem; however, viruses are not always detected in plants with green stem, and virus-infected plants do not always have green stem. Other factors that may contribute to green stem are insect damage, genetic mutations and variety characteristics. Patches of plants with delayed maturity also may be found near billboards, street lights or other artificial lighting.
Hail Damage
Hail tatters leaves and may bruise or sever stems. Wounds from hail damage may allow opportunistic diseases to develop. Plants can recover from hail unless the plants are cut off below the lowest above ground node. Yield loss will depend on severity of damage and growth stage of plants; a crop in reproductive stages suffers the greatest yield loss.
Lightning Damage
Lightning damage is characterized by circular areas of dead plants with clearly-defined edges that develop seemingly overnight. Most, if not all, plants within these spots are killed. Plants at the edge of the spot that are not killed appear brown to black with blanched piths.
Soil Crusting
A hard crust may develop after a driving rain on tilled soils and prevent seedlings from emerging. The seedlings may die before emergence or the hypocotyl arch may break when trying to push through the crust. Seedlings that do emerge may appear bent or twisted.
Sunburn or Sunscald
Sunburn damage appears as brick-red spots between veins on the lower and occasionally the upper leaf surfaces. Spots later develop brownish centers.
