Wheat: Winter Wheat

Producers who intend to grow winter wheat should consider the undertaking as part of the whole farm operation and not in isolation. Several management decisions and operations should be considered, including:

• Get organized: Start preparing for your winter operations well before seeding starts. Note that seeding a winter crop may coincide with harvesting operations of spring-seeded crops. This additional fall workload is manageable if properly planned.
• Know what you are doing: Obtain and review reliable production information, relevant to your area. If you have any questions, call the Agriculture Knowledge Centre (1-866-457-2377).
• Crop rotation: Determine where your winter wheat fits into the overall cropping sequence of your farm. Knowing in advance which field would be seeded to winter wheat allows the farmer to plan stubble and residue management needed to ensure proper seeding and snow-trapping.
• Field selection: In conjunction with crop rotation, ensure that the field selected minimizes risks from diseases, weeds (including volunteer cereals), insects, etc., while at the same time would provide maximum protection from soil erosion, moisture loss, winter damage, etc.
• Weed control: Winter annuals and perennial weeds pose the greatest challenge. Both types of weeds are best controlled in the fall. If left until spring, they must be sprayed before bolting. See the Guide to Crop Protection for recommended herbicides. A pre-seeding burn-off can help break the "green bridge," which allows the wheat streak mosaic virus to persist from year to year. Seven to 10 days without vegetative growth is required to break the cycle if planting on cereal stubble. Avoid fields with quackgrass and downy or Japanese brome.

Stubble

Due to the harsh winters in Saskatchewan, it is imperative that winter wheat is direct seeded in standing stubble to ensure sufficient snow cover. At least eight centimetres of un-packed snow is needed to maintain winter temperatures above critical levels at crown level for winter survival.

Canola or mustard stubble is preferred as it provides the lowest disease, insect and weed risks, and usually provides adequate stubble for trapping snow. Barley and oat stubble may be used. If planted on wheat stubble, disease issues become pronounced. Dry beans, lentils and field peas have poor snow-trapping abilities and should be avoided.

Winter wheat can be sown on chem-fallow as long as there is enough stubble to capture and maintain sufficient snow cover. However, this may not always be the case since the stubble becomes brittle and loses snow-trapping ability. In a study in which 65 winter wheat fields were surveyed, the lowest average snow trapping potential (STP) of 17 was observed on chem-fallow (Fowler, 2000). In this study, winter wheat had a high risk of winter-kill when seeded into fields or areas within fields that had a STP of less than 20, where:

STP = [stubble height (cm) x standing stems per m²] ÷100.

The target STP prior to seeding should be greater than 40. Post-seeding STP should be greater than 20. When seeding, use equipment which preserves the stubble.

Crop residue management begins at harvest. Cut the crop at a height that would provide STP of more than 40. Spread the straw and chaff uniformly. Harrowing before seeding can be an effective way of spreading excess straw; however, harrowing can reduce STP. If a hoe drill is to be used in seeding winter wheat, the straw must be well chopped and spread uniformly. Most no-till drills should be able to seed into stubble left for snow trapping without plugging.

Seeding

Optimum seeding dates range from August 20 in the northeast to September 15 in the southwest corner of the province. The optimum date for no-till seeding winter wheat into standing stubble is:

August 27: Meadow Lake/Prince Albert/Nipawin areas
August 30: North Battleford/Saskatoon/Wynyard/Yorkton areas
September 3: Kindersley/Swift Current areas
September 6: Maple Creek/Estevan areas

The recommended optimum seeding dates are based on seeding dates that provide optimal growth for highest winter hardiness. Plants should have three to four leaves with one tiller, and well developed crowns by freeze up in order to attain maximum cold tolerance and optimum energy reserves. In general, this should be within seven to 10 days of the optimum seeding date. Seeding too early results in excessive growth in the fall and loss of winter hardiness consequently leads to increased winter injury. Late seeding results in poorly established plants with low winter survival potential. Hence, both situations result in poor stands and decreased yield potential.

Optimum seeding rates for winter wheat are similar to those of spring wheat. However, because of winter mortality, the target plant populations should be between 25 and 30 to achieve a spring stand of 18-24 plants per square foot. Base your seeding rate on seed size (thousand kernel weight - TKW), germination percentage, seedling mortality and the target plant density. The calculation is performed as shown below:

Seeding rate (lb./ac.) = [(Plants/ft.² x TKW g x 10) x (% Survival)]

Note that percentage survival is a product of percentage germination and mortality rate. Seeding rate will also vary by region.

Shallow seeding (0.5 to one inch or 1.3 to 2.5 cm.) is generally recommended. This ensures that the seed germinates and emerges without expending too much energy. Ensure that the seed is in good contact with the soil. Unlike spring seeding when farmers may seed deeper hoping to place seed in moist soil, there is no advantage gained by seeding deeper than recommended, since fall stubble soil moisture rarely increases with soil depth. Shallow seeded winter wheat can germinate from a small amount of rainfall. If soil is dry, shallow seeding increases the odds of germination.

Which varieties of winter wheat are best suited for my area?

Refer to the Varieties of Grain Crops for the best varieties for your area. Choose a variety that would provide you with the best yield and resistance to lodging, winter damage, stem rust, leaf rust and bunt. When selecting varieties, marketing should also be considered. Contact your grain merchants prior to purchasing seed.

Fertility

Apply nutrients based on soil test recommendations using a reasonable target yield. Expected price of winter wheat and fertilizer should also be considered for determining economic fertilizer application rates.

Commonly available forms of nitrogen are: urea (46-0-0); liquid urea ammonium nitrate (28-0-0); anhydrous ammonia (82-0-0); and ammonium sulphate (21-0-0-24). For details on the characteristics and usage of these fertilizer options, see Nitrogen Fertilization and Guidelines for Safe Rates of Fertilizer Applied with the Seed.

Phosphate fertilizer must be banded with, or very near, the seed to be effective. The higher the amount of N placed with seed, the higher the risk of seedling damage and winter-kill. Side or mid-row banding of N gives the best results both in terms of protecting the seedling from toxicity and salt effect and increasing N use efficiency. Generally, fall broadcasting N results in increased risk of losses of N to the environment. If seeding is done with double shoot openers, don't sacrifice seedbed quality for fertilizer placement. There are several effective methods of applying N early in the spring.

Winter wheat growers like to assess their winter wheat fields for winter-kill in early spring before applying the N fertilizer. Whatever the case, ensure that the N fertilizer is applied by early spring for optimum results using soil test recommendations. Side banding or mid-row banding all the N fertilizer in the fall is one option and early spring application using one of several methods is another option, for managing fertility in winter cereals. Logistically, winter wheat should be fertilized prior to spring seeding to avoid conflict with seeding operations.

Weed Control

Pre-seeding weed control, including pre-harvest management with a glyphosate product is an effective control measure for biennial and perennial weeds. There are limited herbicides registered for fall post-emergent application to winter wheat.

Canadian labels recommend spring application only, and many indicate NOT to apply in the fall. As a result, the optimum time to treat winter annual broadleaf weeds in winter wheat is as early in the spring as feasible when both winter wheat and winter annual weeds have begun to grow.