Soybean Hail Damage

Trent Irby, Extension Soybean Specialist
By Trent Irby, Extension Soybean Specialist May 30, 2012 17:28

Soybean Hail Damage

Several soybean fields around the state have unfortunately been impacted from hail associated with recent storms. The big question in these cases is whether or not to replant. This is always a difficult question to answer. Several things need to first be considered before making this decision. Factors influencing soybean yield in these situations include growth stage as well as the degree of damage to the plants.

Damaged plant after 72 hours

First, determine the growth stage of the soybean crop. Research has shown that defoliation during vegetative stages has little impact on yield. Typically, yield loss due to reduction in crop stand is less severe during the early vegetative growth stages of V1 to V4 as compared to later reproductive stages of R3 and beyond. Next, get an idea of the surviving plant population 3 to 5 days after the storm in order to determine the total stand reduction. In many cases, yield loss may not be observed for final populations of 75,000 plants per acre or more. If the remaining soybean stand is fairly uniform, then replanting may not be necessary. Look closely for gaps of greater than 2 to 3 feet within the row. If there are areas within the field with frequent gaps, replanting may be the best option. Row spacing should also be considered as wide row (38 to 40”) soybean may not be able to compensate for the lost stand as easily as narrow row (7 to 15”) plantings. Areas with thin stands can become problematic later in the growing season due to increased weed or insect pressure. Another estimate to consider is condition of the surviving plants. Examine the growing point closely. Plants that are cut off below the cotyledons will not typically survive. Leaf tissue that is green and still attached to the plant will continue to function. Finally, get an estimate on the level of stem damage. Some of the damage to the stem may be difficult to observe. Keep in mind that a damaged stem may result in reduced movement of water and carbohydrates to the growing points and/or lodging later in the growing season.

If replanting seems to be the best option, consider the calendar date. We are by no means outside of the planting window for soybean. However, planting at this point will mean a later harvest. Consider the harvest time for the other crops growing on your farm as well as the total number of acres that need to be replanted. When thinking of replanting, look at the long term weather forecast and what varieties are still available from your distributor. If replanting is unavoidable, proper termination of the existing stand is important. Leaving an existing stand and planting a new crop in the same field will often cause more problems than you solve as the old crop can become a weed in this situation. In addition, there will likely be a difference in maturity of the two interplanted crops which can cause issues at harvest.

More often than not it is more profitable to retain the damaged crop rather than terminating the stand and starting from scratch. If an acceptable population is present uniformly across the field, it may be better to keep that crop. If the decision is made to keep the damaged crop, take extra precaution to protect the stand that you have as any further loss in population may have negative impacts on yield.

Remember, hail damage to a soybean crop can often look worse than it really is. Soybean has the capacity to compensate for thin stands. Give the field a few days before making replant decisions. It is possible that new growth will emerge which can give you a better idea of the actual losses sustained from the hail damage.

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Trent Irby, Extension Soybean Specialist
By Trent Irby, Extension Soybean Specialist May 30, 2012 17:28
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