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Dormant Seeding Canola
INTRODUCTION
Dormant seeding of canola can be defined as seeding canola in cold, nearly frozen soil which will inhibit germination that fall. The objective is that the seed remains dormant after planting until early spring. As conditions become favorable in the spring, the canola germinates and emerges. Determining when to seed is difficult, since a grower can’t go by a specific calendar date. The soil needs to be cold, if not frozen (Below or near 32� F in the top 2 inches). If soil temperatures warm to 38� or higher, the seed will germinate and will be killed once the soil freezes. In the past, growers have found it difficult to dormant seed canola the right day as the soil temperatures approached freezing, but before the first snow.
A seed coating is available that is applied to the seed that keeps the canola from germinating in the fall when seeded into warmer soils. The coating gives a grower more flexibility and time to safely dormant seed the canola. It is recommended to plant coated seed within approximately 18 days prior to the soil freezing. If seeded in that time frame the grower doesn’t have to worry about the seed germinating that fall. A grower should be able to safely seed dormant canola in late October or early November. Actual seeding dates will vary depending on the area of the state.
ADVANTAGES:
#Spreads out the spring planting workload. By seeding a percentage of the crop in the fall, more time is available in the spring.
#Similar or higher yields compared to spring plantings. Research results in western Saskatchewan indicate higher yield of dormant canola when compared to early spring plantings. Research results in North Dakota haven’t consistently indicated higher yield of dormant canola compared to spring plantings.
#Dormant canola will compliment spring plantings by spreading out flowering dates. Dormant canola usually flowers and ripens a minimum of two weeks earlier than the earliest possible spring planting. In the two years of dormant seeding research at the North Central Research Extension Center, canola began to flower in late May, two weeks earlier than the late April planting. Spreading out flowering dates will reduce the risk of the entire crop being adversely affected by hot, dry conditions.
#Spreads out the swathing and harvest workload.
#Canadian research indicates that another advantage of dormant seeding is that the crop gets established before the emergence of the flea beetle. That hasn’t always been the case at Minot. In 1998, flea beetle emergence was early which warranted a rescue treatment of Warrior. In 1999, the crop was established prior to the emergence of the flea beetle and was unaffected by any flea beetle feeding pressure.
RISKS:
#Dormant seeding has often been unsuccessful due to seed germination prior to freeze-up in the fall. A seed coating will reduce the risk of seed germination prior to freeze-up.
#Also seed germination following early soil warm-up in the spring results in seedling death when the soil freezes again. This has occurred more often with black soil conditions or where the soil has had less than 30% residue. Dormant seeding into standing stubble will reduce this risk. Standing stubble or fields with a minimum of 75% residue will trap more snow and keep the soil colder longer, reducing the risks of seed germination too early in the spring.
#Fields with inadequate residue have been more susceptible to soil crusting in the spring. Research has shown that stand establishment with dormant seedings have been more consistent in no-till or minimum till compared to soils that have inadequate residue.
DORMANT SEEDING TIPS:
Seed into as much residue as possible. The primary reason dormant seeded canola fails is due to lack of residue. No-till or minimum till seeding which results in 75% residue left after seeding will be less risky and increases success in establishing a stand. Seed the canola � to 1 inch deep. Broadcast seeding is more risky than using a drill or air seeder. Broadcast seeding could result in inconsistent emergence in the spring. Increasing the seeding rate 10 to 15% is a practice to help reduce risk from inconsistent emergence.
HOW TO FERTILIZE:
There are several options for fertilizing dormant seeded canola. One method is a fall application of the recommended rate of anhydrous using knives and place the recommended rates of phosphorus and sulfur when the canola is seeded. There is a concern that the fall applied sulfur could leach out of the seed zone prior to canola emergence next spring. There are several springtime application options. One option is the "wait and see approach." A recommended rate of phosphorus is placed with the seed and the recommended rates of urea and sulfur are broadcast in the spring once the stand has been established. It is recommended to use the ammonium sulfate form of sulfur. Another option is to use a liquid sulfate fertilizer such as, ammonium thiosulfate. The application can be safely applied to canola that has at least five true leaves. Leaf burn will be reduced at this stage because the plant has been able to develop a waxy protective covering on the leaf.
VARIETY SELECTION:
When dormant seeding select a variety that has good seedling vigor. Varieties with good seedling vigor will be more competitive with weeds early in the growing season. They are also more likely to push through a shallow crust. Herbicide tolerant varieties with good seedling vigor might get by with only needing one application of a specific herbicide rather than two applications.
WEED CONTROL STRATEGIES:
Weed control is critical to successful dormant seeded canola. There are many options to consider. A grower could select a herbicide tolerant variety such as Roundup Ready, Liberty Link, or Clearfield (IMI) canola, or plant a traditional canola variety. Keep in mind that with dormant seeding a spring burndown of Roundup most likely will not be an option. The crop typically emerges the same time as does early emerging weeds. Weeds that emerge early in the growing season will also be the most competitive with the canola. Weeds such as winter annuals, shepherdspurse, field pennycress, or tansy mustard, kochia, common lambsquarters, Russian thistle, wild mustard, and wild oat will be the most troublesome weeds with dormant seedings of canola.
WEED CONTROL OPTIONS:
Traditional Canola:
A disadvantage of dormant seeding traditional varieties compared to the herbicide tolerant types is the inability to control broadleaf weeds. There are no pre-emergent or post-emergent herbicides labeled that will control winter annuals such as shepherdspurse, field pennycress, or tansy mustard. Since a spring burndown of Roundup is not an option, a grower will be very reliant on a dinitroaniline herbicide for broadleaf weed control. Trifluralin and Sonalan are the only pre-plant herbicides labeled for canola that will control some broadleaf weeds. Sonalan will give better control of hard to control broadleaf weeds such as kochia and Russian thistle than Trifluralin. It is very important to keep in mind when applying either herbicide, that maintaining as much residue as possible is important for the success of dormant seeding. Applying Sonalan or Trifluralin at the high rates with a harrow or rotary hoe is an option to consider. Applying either product with spikes or sweeps is not recommended. Research has shown that surface applying Sonalan granules has given good results in fields that have been in a no-till system for two or more years, where weeds are concentrated in the top inch of the soil.
Roundup Ready Canola:
Roundup Ready canola has an advantage over traditional canola due to the broad spectrum of weeds controlled postemergence. It will be very difficult to get by with only a single one pint per acre application. There most likely will be a heavy flush of weeds at the time the canola is emerging. These weeds will be very competitive and an application of one pint is recommended when the canola is at the cotyledon to 2-leaf stage. Canola remains in the rosette stage for the first four weeks of development. This allows later emerging weeds to become competitive. A second application of 1 pint per acre might be necessary prior to bolting to control the later emerging weeds. If wild oat is not present and weed emergence is delayed compared to the crop, then one application at 2 to 4 leaf may be sufficient. If weed populations are low, then only a single application maybe required.
Liberty Link Canola:
Liberty Link also has an advantage over traditional canola due to the broad spectrum of weeds controlled. Liberty Link weed control strategies will be similar to Roundup Ready. Liberty is more effective on annual broadleaf weeds but weaker on annual grasses compared to Roundup. At the present time, it is recommended to apply one application of Liberty at 34 fluid ounces per acre. It will be very difficult to control all weeds with one application. Split applications at reduced rates at cotyledon to 2-leaf followed by a second application prior to bolting should be considered. Although two applications will not be convenient, early emerging wild oat or high populations of other weeds will usually cause yield reductions in a one-pass program. If wild oat or volunteer cereals are not present and weed emergence is delayed compared to the crop, then one application at 2 to 4 leaf may be sufficient. If weed populations are low, then only a single application maybe required.
Clearfield (IMI )Canola:
Beyond will control a broad spectrum of weeds including most winter annual species, wild mustard, kochia, wild oat, and foxtail species. Beyond is in the same family as Ally, Peak, and Express and will not control kochia that is resistant to the ALS herbicides. Due to the fact that ALS-resistant kochia is a major concern, a grower might want to fall apply Sonalan as discussed in the traditional canola paragraph followed by a spring application of Beyond for the control of winter annuals, wild mustard and annual grasses.
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