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Direct seeding of winter wheat into standing stubble is a viable cropping option for many producers in Alberta. Snow trapped in the stubble insulates wheat seedlings against cold temperatures, reducing the risk of winter kill.
New winter wheat varieties have good straw strength and out-yield hard red spring wheat. Winter wheat can make more efficient use of early spring moisture, before soil moisture is lost later in the summer.
The seeding and harvesting windows for direct seeded winter wheat are greater than those for most spring crops. This helps to spread the farm workload.
Winter wheat can also extend crop rotations. Seeding it into stubble from broad-leaved crops, such as canola, mustard and peas, will reduce the risk of insect, disease and weed problems for all crops in the rotation.
Most direct seeding systems leave the stubble relatively undisturbed, helping to improve spring soil moisture reserves and reduce erosion potential. A direct seeded winter wheat crop also provides excellent spring nesting cover for several bird species.
Crop Establishment
Establishing a good stand of winter wheat requires shallow seed placement, planting at the optimum time and proper fertilization.
Seeding depth
The recommended seeding depth for direct seeded winter wheat under optimum conditions is less than 1 inch (2.5 cm). Shallow seeding is critical because deeper seeding results in delayed emergence and less vigorous plants.
Seeding equipment must be adjusted for shallow seed placement. Shallow seeding reduces production costs, because less horsepower is needed to pull the drill at shallow depths. Seeding equipment must be able to place seed into all types of crop residue without plugging. Packing is essential to ensure good soil-to-seed contact, especially in drier soils.
Seeding date
Direct seeding of winter wheat lengthens the conventional fall seeding window due to increased protection from winter kill. Optimum seeding times for several areas of the province are shown in Table 1. In general, seeding dates are earlier as you move north and east in Alberta.
Table 1. Optimum seeding time for winter wheat
Area | Range of dates* |
| Lethbridge | September 10 to 20 |
| Lacombe | September 1 to 10 |
| Vermilion | August 25 to September 5 |
* year-to-year differences because of weather variability.
Seeding too early may result in lower yields and smaller seed size. Seeding too late may result in lower yields, reduced winter hardiness, increased weed problems, delayed heading, delayed maturity and reduced bushel weight. Figures 1, 2 and 3 show how the seeding time can affect these factors.
Figure 1 Influence of seeding date on winter hardiness (field survival index) of winter wheat
Figure 2 Influence of seeding date on yield of winter wheat
Figure 3 Influence of seeding date on maturity of winter wheat
Figures 1, 2 and 3 are reprinted with permission from D.B. Fowler and Ducks Unlimited Canada from: D.B. Fowler. 1993. Chapter 7, Stubbled-In Winter Wheat Seeding Date and Depth, In: , Ducks Unlimited Canada and Conservation Production Systems Limited. Saskatchewan researchers have shown that the time for germination shortens from 7 days at 5°C to only 1.5 days at 20°C. They also showed that moisture at seeding was not as critical as temperature. Winter wheat seeded into a dry soil on the optimum seeding date germinated with as little as 9 mm (0.3 in.) of rain.
Seeding rate and seed row spacing
Winter wheat has the ability to tiller, compensating for thin stands. However, highest grain yields are consistently achieved with narrow row spacing at seeding rates higher than most producers currently use for spring wheat.
Soil Fertilizer Management
Nitrogen and phosphorus are the two nutrients most frequently limiting to winter wheat yield and quality. Soil sampling and testing are recommended when planning nitrogen and phosphorus rates for each field.
Nitrogen
Nitrogen can be successfully applied:
- before seeding with a banding operation
- during seeding, either seed-placed, side banded or mid-row banded
- in early spring by broadcasting
Each method has advantages and disadvantages.
Banding before seeding: Nitrogen in the form of anhydrous ammonia or urea can be banded before seeding. In dry years, banding operations may result in a lumpy, dry seed bed, causing reduced crop germination and yield.
Nitrogen at seeding: Nitrogen fertilizer can be seed-placed or banded during seeding. Banded fertilizer should be placed at least 1 inch (2.5 cm) from the seed to avoid crop injury. Safe rates of seed-placed nitrogen are similar to those for spring wheat. Risk of injury is usually higher with urea than ammonium nitrate forms and with drier soils. Saskatchewan research has shown that low rates of seed-placed nitrogen can reduce cold hardiness of winter wheat. However, southern Alberta research has not shown any effect on direct seeded winter wheat survival with low to moderate rates of seed-placed nitrogen.
Spring-applied nitrogen: Broadcasting nitrogen in early spring, immediately after the soil has thawed, can provide a consistent, predictable yield response. Winter wheat plants normally take up 90 per cent of their nitrogen requirements before heading. Delaying application until early June results in limited yield response.
Phosphorus
Phosphorus should be placed with the seed at rates of 15 to 25 pounds per acre (depending on the results from the soil test). Research in Alberta has shown that seed-placed phosphorus is usually more effective than banded phosphorus. Insufficient phosphorus may reduce plant vigour, winter survival, crop yield and crop quality.
Other nutrients
Soils should be tested for other nutrients like potash, sulphur and copper. If any of these nutrients are below a critical level, additional fertilizer may be required.
For more information on fertilizer management, refer to Agdex 541-1 Alberta Fertilizer Guide.
Weeds
Weed control starts with a proper crop rotation and a vigorous stand of winter wheat. Wild oats and annual broad-leaved weeds are usually not a concern. Winter annual and perennial weeds pose the greatest challenge.
Winter annual weeds, such as flixweed, stinkweed and shepherd's purse, are controlled in late fall or early spring by using 2,4-D or MCPA. Downy brome is a grassy winter annual with a growth habit similar to winter wheat. Sencor can be used for control in the spring, but winter wheat should not be seeded into fields infested with downy brome.
Roundup/Laredo/Wrangler/Renegade/Victor, Touchdown or Rustler can be used before seeding in the fall. Several product options are available for control of broad-leaved and grassy weeds in the spring.
Always consult with the latest edition of Alberta Agriculture, Food and Rural Development's Crop Protection(the "blue book", Agdex 606-1) for information on products, procedures and rotation restrictions. Read and follow all product labels and directions carefully.
Insects and Diseases
Winter wheat is susceptible to many of the same diseases and insect pests as spring wheat. Seed treatment helps to establish healthy stands and control bunt and loose smut problems. Crop rotations are critical to preventing and controlling foliar and root disease problems. Snow mould can be a problem in the Parkland areas of Alberta.
Winter wheat is a host for sucking insects such as plant bugs and aphids. The Russian wheat aphid has caused some problems in southern Alberta in the past few years, but to date has been a relatively minor problem. Plant later or use a foliar insecticide if the Russian wheat aphid is a concern.
Wheat streak mosaic can be very destructive to winter wheat. To date, this disease is only a problem in southern Alberta. Yellow streaking of the leaves and stunting of the plant in late fall or early spring are common characteristics of the disease. Early infection causes pronounced premature yellowing and may result in destruction of the entire crop.
The wheat streak mosaic virus is transmitted by the tiny wheat curl mite. The mites and the virus require living plants to survive. They must have a "green bridge" - green plants to bridge the transmission of the virus to another crop. To effectively control the virus, the transmission cycle must be broken by ensuring that spring wheat crops have ripened before seeding winter wheat. Volunteer wheat plants are also important sources of virus transmission and must be controlled before seeding. For more information, refer to Agdex 112/632-3 Wheat Streak Mosaic in Alberta and its Control.
Crop Residue Management
Crop residue management is essential for successful direct seeding. Properly managed crop residues provide several benefits, such as increased crop yields and improved erosion control.
Chaff rows and poorly spread straw can create many problems including:
- concentrations of weeds and volunteer grain growth where the harvester has travelled
- uneven field fertility and moisture holding capacity
- clearance or plugging problems in seeding operations
- poor seed placement which interferes with germination
- uneven crop ripening.
Large amounts of crop residues create high levels of microbial activity. This can temporarily immobilize crop nitrogen, creating early season nutrient deficiencies. Winter wheat is especially dependent on early season nitrogen.
To successfully overwinter a winter wheat crop, the standing stubble must uniformly trap snow across the field. It must also trap an adequate snow cover before soil temperatures approach critical levels for the crop. Stubble height should be at least 6 to 8 inches (15 to 20 cm) for effective snow trapping. Straight combining provides the tallest stubble, but very tall stubble may cause plugging of seeding equipment. Trapping snow also increases spring soil moisture for improved seedling growth.
For more information, see Agdex 570-4 Residue Management for Successful Direct Seeding, Agdex 519-4Equipment Issues in Crop Residue Management, and Agdex 519-2 Handling Difficult Crop Residue Conditions.
Summary
Winter wheat is a viable cropping option for many farmers who have the capability of direct seeding. As with any system, it requires planning and management for success. Direct seeded winter wheat is an environmentally friendly cropping option that can help farm profitability.
For more information
Other winter wheat publications include Agdex 112/20-3 Winter Wheat Production and Agdex112/11-1 Winter Wheat in the Parkland Area of Alberta. All of these publications are available from the Publications Office, Alberta Agriculture, Food and Rural Development, 100A 7000 - 113 Street., Edmonton AB, T6H 5T6.
Prepared by:
Rob Dunn , Alberta Agriculture, Food and Rural Development, and Donna Fleury , P.Ag.
Source: Agdex 112/22-1 Revised March 1998.
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