Damaged Soybeans Caused by Waterlogged Fields

By Rebecca Vandersleen, Farms.com

Soybean plants are being affected throughout the Midwestern area of the United States from Tropical Storm Bill, which is causing heavy rain to be applied to already wet fields.  This tropical storm began earlier in June, and is expected to continue to affect farmers’ fields for the next couple of days.  These downpours caused a spike in soybean pricing as fears spread that yields will be much lower than originally expected.  

It is important to understand how to assess the factors that contribute to yield loss for soybean plants.  Soybeans cannot thrive in waterlogged fields due to the simple fact that they need oxygen in order create energy.  The oxygen they need is normally procured from the soil, which cannot happen if there is too much water.   The risk for yield loss increases the longer the fields remain saturated.  Generally, if soybeans are in a waterlogged field for 4 days or more it can seriously affect the yield, sometimes up to approximately 40 percent. The soybeans will most likely die if the conditions do not improve within 6 days.  

High temperatures can also decrease yield.  A sunny day with temperatures above 26 degrees Celsius provides poor results for soybeans as it promotes a greater reduction in oxygen.  This tends to occur most when soybean plants are in a later stage of development.  Saturated fields can also lead to Phytophthora, which is a soil disease that rots the stem and roots of the plant.  Phytophthora would be likely in these circumstances as it thrives in wet and warm conditions.  Weather is not the only determining factor for field conditions; tile drainage, and the soils texture and structure can also control how long the soil remains wet.  

Once fields begin to dry up, farmers can judge how much damage was caused.  If new shoot growth is spotted, this is certainly a good sign.  Root nodules can also be examined.  White, reddish pink and firm nodules mean the plant is still doing well.  If this is not the case, one may want to consider a nitrogen fertilizer to promote proper nitrogen fixation.