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Melissa Bartels

What’s going on in Ag? Statewide we have experienced above normal precipitations for the month of May, Butler County received 175 to 200 percent above normal. However, you may be wondering how crops handle saturated soils and/or standing water on planted and emerged crops. The impact flooding will have on crops will depend on the seed’s genetics.

What we know about flooded corn: Water saturation creates anaerobic conditions for corn, both plants and roots need oxygen to respire and survive, without oxygen a fermentation process occurs. Anaerobic conditions in soils can result in nutrient leaching, denitrification, and toxins released by organic compounds. In corn, warmer soil and air temperatures during flooding increase the degree of plant damage. The development state at which corn is flooded affects plants' response and the damage to the crop increases with the length of the flood. Unfortunately, there is a point at which the crop will not recover from being flooded. Research has shown that corn before the sixth leaf stage; under six inches of water with an air temperature less than 77 degrees Fahrenheit could survive for four days. Flooding lasting longer than four days resulted in lower corn yields and lower nitrogen levels. An increase in plant pathogens such as seed rots and seedling blights occur with flooded conditions.

Another study revealed, the longer a plant root is flooded the greater the injury potential. The corn’s root growth stops within 24 hours of flooding. Three to five days of flooding negatively affects root mass, viability, and maximum depth. Corn at V4 that sustains flooding for five days is susceptible to root damage, while the most tolerant growth stage to flooding is stage V8. Roots of plants flooded at either V12 or R1 are never able to recover fully. Unfortunately, when corn stands in waterlogged, saturated, or flooded soils, the plant goes into a defensive mode and shuts down. Depending on the duration of the flooding and the growth stage of the corn, it will likely never recover.

What impact does flooding have on soybeans? One study looked at how germinating soybean seeds respond to flooding, it determined germination is reduced by more than 20% when seeds are flooded for one to 48 hours, one day after imbibition (the process in which the seed fills with water). If seeds are flooded for two days beginning two or three days after imbibition, germination is reduced by 50 - 70 percent. Severe losses can occur when soybean seeds are flooded for four days or more. Cooler soil temperatures improve soybean seed viability when seeds are exposed to flooding.

Soybeans in the vegetative stages can endure a fair amount of flooding without major impacts. Research has shown that soybeans can usually survive for two to four days underwater. Cooler temperatures and cloudy conditions increase the survivability of the soybean plant during flooding. Higher temperatures and sunshine increases plant mortality because plant respiration rates increase, depleting oxygen and increasing carbon dioxide levels. Soils saturated prior to flooding will result in more rapid soybean mortality because the water blocks the gas exchange between the rhizosphere and the soil surface. Soybeans subjected to flooded conditions are more susceptible to several pathogens such as Pythium Seed and Root Rot, as well as Phytophthora Root and Stem Rot.

For updated information on crops in Nebraska, please visit UNL CropWatch at https://cropwatch.unl.edu/.

For more information on flood resources please visit https://flood.unl.edu #NebraskaStrong

• Nebraska Farm Hotline/Rural Response Hotline: 800-464-0258

• Nebraska Family Helpline: 888-866-8660

If you have any questions, please contact me at 1-402-367-7410 or by email at Melissa.Bartels@unl.edu.

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