By David Karki
One of the major winter crops grown in South Dakota is winter wheat, although winter rye and triticale are grown in smaller areas. According to USDA-NASS, about 800,000 acres were seeded to winter wheat in SD in fall 2018. In normal circumstance, 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 re-growing or ‘greening up’. During the over winter process, snow plays an important role as snow not only provides the insulation needed to regulate the extreme fluctuation of air temperatures but also moisture as it melts. However, too much snow may create water logged or flood conditions in the field, especially in the lower grounds which could be a worrying scenario for lots of winter wheat grower.
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 the temperature—higher rate of oxygen depletion in higher temperatures. For instance, plants can experience severe flooding injuries in submerged conditions of 48-96 hrs during summer months. Research shows, when temperature is above 65°F, flooding conditions can lethal in as few as 48 hrs. In SD, in current conditions, with 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, plant don’t require as much oxygen as actively growing plants and can tolerate flood conditions for more prolonged period. Another factor that can affect the winter wheat growth is the ice build-up due to cold-thaw cycle which can completely block the gas exchange process.
Every winter, growers are curious if their wheat field will survive the winter; and like with any other winter injury, there is no easy way to find out if all or any wheat plants on icy patches survived. One way to find out is to inspect the field after plants start to regrow with the rise in daily temperatures. Another indoor method outlined below can be used prior 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 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.
Other factors that flooding can generally impact is the 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.
Source: sdstate.edu