The key to successful winter wheat production is winter survival. The most successful management factor to help ensure winter survival is seeding into standing stubble that will catch and hold snow. A blanket of snow will help protect the seeded winter wheat crop by preventing soil temperatures from dropping to lethal temperatures.
To optimize winter survival, stubble needs to hold four inches or more of snow. This can be accomplished either with stubble providing a lot of short sticks or few taller sticks (see Table 1). Please note that this is the amount of standing stubble required after seeding, so one may need to up to two times this before seeding if the seeding operation knocks down a lot of stubble.
SEED A CROP FOR STUBBLE
Ideally stubble should consist of stiff stems and not just upright leaves. When vegetative plants are terminated with glyphosate they are likely to lie over and decompose, contributing more to seeding problems than as snow-trapping stubble. But some weeds, providing they produce upright stems, can also serve the purpose. However for farmers this will be a compromise in how long they can leave weeds to consume water and produce stubble versus their potential for reseeding with more weed seeds.
The following are some options for stubble production:
1) Cereals could be seeded for greenfeed and to dry out soils. They can provide very good snow-trapping stubble but offer some challenges. Cereals may increase potential risk of diseases such as tan spot and septoria. Risk of wheat streak mosaic virus infection is also high as the wheat curl mite (which transmits this disease) can move from an immature cereal crop to the winter wheat. Control with herbicide all volunteer host plants (immature cereals) and regrowth at least two weeks prior to planting winter wheat as the mite cannot survive longer than 10 days without living cereal plants. Field margins should also be sprayed to control the grassy weeds that can harbour wheat curl mite.
2) Leave any canola or cereal stubble remaining from 2009 crops untouched. Weeds and volunteer crop can be left to grow and use soil water until weed seeding is a problem. Stubble could then be sprayed with glyphosate. When stubble amounts are low (either low density or short in height), it is best to equip seeders with low-disturbance, narrow openers to leave as much as possible standing. In the past, farmers have also observed their greatest winterkill on headlands, where first combines, then seeders turn and subsequently flatten the stubble. One possible solution is to simply seed several more rounds around the field, thereby positioning the seeder headlands well within the field. This reduces turning on the same areas and keeps more stubble standing.
3) An annual crop could be seeded to produce adequate stubble and use soil moisture. Stubbleproducing plants that have been evaluated with some success are mid-July-seeded flax and Polish canola. Cereals will produce ground cover and use soil moisture but may not provide sufficient stiff stubble unless stems are cut (along with disease concerns, as mentioned earlier). In general it takes five to six weeks of plant growth to produce stubble. With this stubble production option, seed supply and price can influence decisions.
Production of the above stubbles should be done on the cheap, unless some income is to be generated by them. Fertilizer applications should be minimal. Herbicide use should focus on low cost, low residual products.
Other management strategies that should be used to help ensure winter survival include:
1) Seeding earlier than normal in late August to produce a well-established plant with three or more leaves and tillers with a fully developed crown that is more winter hardy than less fully developed plants.
2) Seeding four weeks early (mid- August) actually increases chance of winterkill. Seeding too early allows the crown and cells within the crown to become very large and susceptible to freezing, and excessive vegetative growth leaves plants more susceptible to disease infection.
3) Seed placing a substantial rate of phosphorus (30+ lb. P2O5/ac) will increase winter hardiness and recovery from winter injury. Increase seeding rates aiming for at least 25 plants established per square ft.
4) Check winter hardiness of the wheat variety. For varieties commonly grown in your province, please refer to your provincial seed guide.
5) Lastly, consider planting fall rye since it is more tolerant of colder temperatures than winter wheat.
AdaptedfromManitobaAgriculture,Food andRuralInitiatives’CropE-NEWS,originally preparedbyPameladeRocquigny,MAFRI cerealsspecialistandJohnHeard,MAFRI cropnutritionspecialist.
Table 1. Recommended stubble height and density to achieve suitable snow catch for winter survival (adapted from Winter Cereals Canada)