Winter Wheat Planting Considerations

Sep 17, 2021

By David Karki

South Dakota is unique for growing both types of wheat, spring and winter, in almost equal proportion. According to the U.S. Department of Agriculture National Agricultural Statistics Service (USDA NASS), 630,000 acres were planted to winter wheat in 2020 and 770,000 were planted to spring wheat. Although vegetative characteristics of these two wheat types are very similar, there are distinct differences between the two in terms of withstanding freezing temperatures and the requirement of colder temperatures to produce seeds.

Early fall winter wheat growth

Early fall winter wheat growth in in Codington County, South Dakota. Courtesy: David Karki

Winter Wheat Planting Time

As we move into the fall season, winter wheat growers always ask that one question: What is the best time to plant winter wheat? Winter wheat, if planted too early, can have disease and insect problems, which can persist to next season; if planted too late, it can get winter killed, which can result in uneven stands and severe yield impact. A multi-year study conducted in South Dakota showed that the optimum window to plant winter wheat ranged from Sept. 10 to Oct. 10, moving from south to north. Depending on the fall weather conditions, planting into October may not provide the plants for ideal fall growth (i.e. two-to-three tiller stage) before winter dormancy.

Seeding Rate and Variety Selection

Like with any crop, the best management decision starts with selecting the best available variety. While selecting a variety, it is critical to assess, not only the yield, but the regional adaptability within the state. Winter hardiness, lodging score and disease tolerance are some of the other important characteristics to consider while selecting a winter wheat variety. The South Dakota State University (SDSU) Crop Performance Testing program publishes yields and other important agronomic characteristics of wheat (and all major crops). The 2021 winter wheat data can be accessed on our Winter Wheat Variety Trial Results page.

The recommended seeding rate of winter wheat is 1.2 million pure live seeds (PLS), or about 28 live plants, per square foot.

Cold Acclimation

Newly emerged winter wheat seedlings in early fall are no different than spring wheat seedlings. In order to survive through cold winters with subfreezing temperatures, winter wheat has to be exposed to a series of cooler temperatures early in the growth stage, which is called ‘cold acclimation,’ or simply ‘hardening.’ The acclimation is possible due to the gradual decrease in daily temperatures in the fall after the wheat has emerged. Winter wheat plants adapt to rapidly decreasing temperatures in late fall or winter by lowering moisture content of the ‘crown’ (the growing point at the base of the shoot), decreasing the accumulation of carbohydrates and slowing down the overall growth process. This greatly helps with frost resistance and other winter conditions that a winter wheat plant has to go through during its life cycle. Cold acclimation generally starts when the temperature starts to fall below 50 degrees Fahrenheit.

Vernalization

Once cold acclimation is achieved, winter wheat requires to go through an extended period of below 40 degrees Fahrenheit temperatures to trigger its reproductive phase the next spring. The amount of time and range of temperatures required varies among varieties. Winter wheat varieties that are adapted to northern climates are usually more tolerant to extended subfreezing temperatures than those adapted to southern environments. The most winter-hardy varieties can withstand crown temperatures as low as -15 degrees Fahrenheit. Better winter survival is achieved when winter wheat is seeded into crop stubble (or no-till) and plants in the fall are at the three-to-four tiller stage before dormancy. Crop stubble helps hold snow throughout the winter and forms an insulating blanket, preventing plants from suffering by extremely low temperatures. Further, snow also plays a major role in providing the moisture needed the following spring.

Source : sdstate.edu

Video: Turning Plant Defense Into a Management Strategy

Turning Plant Defense Into a Management Strategy

Understanding how a plant responds to stress is one thing.

Using that knowledge to make better management decisions is another.

Systemic acquired resistance, or SAR, is the plant's more direct defense response. When stress or infection occurs, the plant begins signaling throughout its system and preparing defensive compounds.

But if we know that response exists, can we help prepare the plant before the stress arrives?

The answer starts with understanding what triggers the response and what the plant needs to carry it out.

The Trigger and the Fuel

Salicylic acid plays an important role in triggering the SAR pathway.

Think of it as turning the truck on.

The engine may be running, but it still needs fuel to do the work.

In this case, manganese plays an important role in supporting the enzyme systems involved in the plant's defensive response.

This makes manganese status an important part of the conversation. Whether a producer is using tissue testing, sap analysis, or simply scouting for visible deficiency symptoms, the goal is to make sure the plant has adequate manganese available.

Manganese is required in relatively small amounts, but that does not make its role small.

If the plant receives a signal to defend itself but lacks the nutrition needed to support that response, it may struggle to carry out the process efficiently.

The trigger matters.

The fuel matters too.

Prepare Before the Stress Arrives

The best time to think about stress management is before the plant is overwhelmed.

Once a crop is already struggling, management can quickly turn into a game of catch-up.

This is similar to nitrogen management. Once a plant becomes severely deficient, correcting the problem does not necessarily erase the time and yield potential already lost.

Plant defense can work the same way.

Low-rate, targeted approaches designed to support the SAR pathway may fit best ahead of an expected stress event rather than after significant damage has already occurred.

That requires producers to think about predictable stress.

We may not know exactly what the weather will do tomorrow, but we generally know summer heat is coming. We know certain field conditions increase disease pressure. We know a herbicide application can temporarily stress a crop as the plant processes the chemistry.

Even a properly timed and labeled herbicide application can create a temporary response in the plant.

That does not mean the herbicide is bad.

Weeds can create significantly more yield loss than the temporary stress caused by controlling them.

The question is not whether we should eliminate every stressor.

The question is whether we can better prepare the plant to manage necessary and predictable stress.

Not All Stress Is Bad

Stress is a normal part of plant growth.

A perfectly stress-free environment does not exist in the field.

In fact, some stress is necessary for normal plant development. A plant responds to wind, temperature, moisture, sunlight, and countless other environmental signals throughout the season.

The environment is stress.

The plant's job is to manage it.

Problems begin when the stress load becomes greater than the plant's ability to respond.

Extreme heat, drought, high salt concentrations, disease pressure, and even certain management practices can add to that load.

This is where understanding SAR becomes useful.

Instead of waiting until the plant is visibly struggling, producers can begin identifying periods when stress is likely and make management decisions around those windows.

ISR Starts With the Soil

While SAR is a more direct defense response, induced systemic resistance, or ISR, brings the conversation back to soil health.

The longevity of a farm is closely connected to the health of its soil.

Carbon plays a major role because it supports biological life within the soil. Bacteria, fungi, and other organisms interact with plant roots and influence how the plant grows, accesses nutrients, and prepares for stress.

This is why soil health cannot be reduced to one product or one application.

It is a system.

Keeping living plants in the field longer can support biological activity. Cover crops may fit some operations. Better water management can improve soil conditions.