One of the major winter crops grown in South Dakota is winter wheat, with winter rye and triticale making only a minor contribution. According to U.S. Department of Agriculture National Agricultural Statistics Service (USDA NASS), about 830,000 acres were seeded to winter wheat in the fall of 2022. Due to extreme drought, many producers who had plans to grow winter wheat were forced to change their mind in 2022. After an extremely dry year, we are seeing significantly higher than average winter precipitation, which is much needed and will likely help replenish our soil moisture levels for upcoming season.
In normal circumstances, wheat seedlings after gradual acclimation to cooler fall temperatures go into dormancy and remain dormant through the winter months. Once the temperatures start rising again in the spring, wheat plants start to regrow or “green up.” During the overwintering process, snow plays an important role, as it not only provides the insulation needed to regulate the extreme fluctuations of air temperatures, but also adds soil moisture as it melts. However, instant melting (due to sudden rise in temperatures) may create water-logged or flooded field conditions, especially in the low spots, which could be a worrying scenario.
Understanding Flood Impacts
One question that usually comes up is, “How does the spring flooding impact winter wheat survival?” Plants in general get affected by water-logged conditions due to lack of oxygen. One of the most-important factors in oxygen depletion is temperature: higher rate of oxygen depletion occurs in higher temperatures. Plants can experience severe flooding injuries in submerged conditions of 48 to 96 hours during summer months. Research shows, when temperature is above 65 degrees Fahrenheit, flooding conditions can be lethal in as few as 48 hours. In South Dakota, in current conditions, with a significant amount of snow still left on the ground and average daily temperatures lower than average, it is safe to say that most of the winter wheat plants are still dormant. While in dormancy, plants don’t require as much oxygen as actively growing plants and can tolerate flood conditions for more-prolonged periods. Another factor that can affect the winter wheat growth is the ice build-up due to freeze-thaw cycles, which can completely block the gas exchange process.
Spring flooding can generally impact other factors, such as root growth, disease incidence, and soil fertility. Although, nitrogen can denitrify and leach beyond the root zone in flooded conditions, the rate of denitrification is significantly slower in cooler temperatures than during summer months.
Inspecting Your Fields
Every winter, growers are curious if their winter wheat will survive the winter; and like with any other winter crop, there is no easy way to find out if all or any wheat plants survived. One way to find out is to inspect the field after plants start to regrow or “green up” with the rise in daily temperatures. Another indoor method outlined below can be used prior to greening up to estimate the extent of the damage in the field.
- Dig up whole plants from the suspected area at least three inches beneath the soil surface containing the plant crown.
- Bring plant samples to room temperature to thaw out.
- Wash off soil from the roots using cool water.
- Cut off fall growth to within 1 inch above the crown and roots below the crown.
- Rinse the crowns with cool water.
- Place 10 wet crowns in a plastic bag, inflate the bag, and tie shut.
- Place the bags in a lighted room, but not in direct sunlight.
- Check the crowns in two days, rinse with cool water, and re-inflate the bag.
- After four days, the crown should show about two inches of new growth.
- Plants that do not show any growth after six days can be considered dead when estimating survival.
Flood Impacts Winter Wheat. J. Ransom, North Dakota State University Extension.