Weed management questions this week
When do I spray after a frost? Weeds need to be actively growing and need enough living leaf area to take up the herbicide. Make sure weeds have recovered and frost loss is less than 40 percent of the leaf tissue. Also, spray on a warm sunny day to improve uptake. More frost tips. Different management for perennials, winter annuals or annuals.
What is the herbicide carryover risk after the dry summer? Residual herbicides need (1) soil moisture near the surface, (2) warm soil temperatures and (3) time for breakdown to occur as expected. Areas with very low moisture accumulation through June, July and August will be at highest risk for herbicide carryover into next year. Consider this when making cropping decisions. BASF notes that canola is particularly sensitive to group 2 herbicides containing imidazolinone-based chemistries and advises growers to avoid planting canola in black, grey and dark brown soils receiving 125mm or less over this period, and the same in brown soils receiving less that 125 mm and additionally receiving less than 15mm in any single month. Please reach out to any herbicide manufacturer for rotational details on specific products. Saskatchewan herbicide carryover risk maps.
Harvest is over and fields have a lot of canola regrowth. What should I do with it? One option is to leave it and let frost take care of it. However, plants will take up nutrients (which will be returned eventually) and some may overwinter. If spraying, use a tank mix that will control the plant. On Roundup Ready canola, tank mix glyphosate with 2,4-D (the glyphosate will control other weeds present).
Can I treat canola regrowth like a bonus cover crop? Regrowing plants will take up nutrients and moisture. That may be enough reason to spray them. This ‘cover crop’ could be feeding microbiology in the soil, so curious farmers may want to leave strips to compare both treatments.
What can I spray this fall on fields planned for canola next year? A helpful table.
Harvest management questions this week
Should I wait for a frost before straight combining canola? If crop is too green to harvest, but seeds are ready, frost can provides some extra dry-down of green stems.
What are the best conditions for pre-harvest spray efficacy? This is related to the question above because cool temperatures will reduce diquat (Reglone) performance.
What is that white powder coming off canola plants? This is powdery mildew. Black “sooty mould” will be alternaria or cladoporium. Powdery mildew in canola will be Erysiphe crucifearum. Powdery mildew thrives in dew-forming conditions – warm dry days and cool humid nights. Rainfall actually inhibits production and spread of conidia. Powdery mildew in canola will not be an issue for pea crops next year: The mildew species is different, plus most pea cultivars are resistant.
What are the major storage risks this year? Sprouted seeds, small seeds and high levels of green dockage (from picking up regrowth, for example) are the more common storage risks this year, but moisture, high temperatures and green seeds will also raise the risk for some growers. In all cases, turn on aeration to remove moisture and cool it down, and then monitor bins. CCGA has good information on dockage and grading.
Fertilizer management questions this week
Why should I get a soil analysis? Soil tests this fall will show nutrient levels left in the field – useful information to set next year’s fertilizer rate. Drought stressed crop will leave a lot of nutrients in the soil and current fertilizer prices are higher than last year.
How many samples should I submit, per field? One composite sample, produced from 15 to 20 cores, can be enough. But if you want to compare nutrient levels on hill tops, side slopes and low areas, at least three composites per field will be required for zone analysis. Four soil samling strategies.
Are soils cool enough for soil sampling and fall fertilizer application? For a soil test that more closely reflects nutrient availability next spring, take a sample after soils have cooled to below 10°C.
What is the best method for fall fertilizer application? Place urea or anhydrous ammonia in a band in the soil. Apply after soil temperatures have cooled to less than 10ºC on well drained sites, and less than 5°C on poorly drained sites. If logistical reasons have you banding nitrogen into slightly warmer soils this fall, use an enhanced efficiency nitrogen source. Timing and tips.
What to look for in a canola cultivar?
September is a busy month for seed purchases. To choose the right seed for each field, consider disease management, days to maturity, harvest traits as well as seed treatment. This Canola Watch article explores a range of scenarios.
This September 2021 Canola Digest article on pod shatter is popular. How to improve yield with genetics. We also encourage clubroot-resistant canola for all areas. To compare cultivar performance over multiple years, check out the grower-funded Canola Performance Trials.