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Canola growers and agronomists can use these steps to improve canola yield (as much as possible) in drought-like growing conditions.
1. Leave tall stubble
- Phillip Harder, research director and hydrological scientist with Croptimistic Technology Inc. and formerly with the Centre for Hydrology at the University of Saskatchewan, researched the relationship between stubble and soil moisture. He found that in dry conditions, snow trapped in stubble and available to infiltrate in the spring doubles when you increase stubble height from 10 cm (4”) to 20 cm (8”), and benefits increase up to about 30 cm (12″ ).
- Michele Konschuh and Dilumi Liyanage, researchers at the University of Lethbridge, ran a meta-analysis of North American research and concluded that tall stubble (30 to 45cm) also reduced wind speed, soil drying and evapotranspiration, effectively increasing water use efficiency. They noted that if stubble needs to be incorporated, spring stubble incorporation provided better water use efficiency and seed yield than fall incorporation.
- Mike Palmier, agronomist with Max Ag Consulting at Plenty, Saskatchewan, recommends that growers in drought-prone areas leave as much stubble as possible – especially for hilltops that need moisture the most. Palmier calculated that each 1” of snow accumulation increased returns for the following canola crop by $15 per acre. In dry conditions, tillage also dries out the top layer of soil and increases erosion potential of the seedbed area.
2. Seed between the stubble rows
This works in tandem with tall stubble. Precision seeding tools that allow for seed placement between rows of tall stubble will result in fewer complications from the tall stubble. This also improves seed placement, which should reduce seedling mortality. Combines set to achieve good uniform residue spread are also important to seed placement.
3. Choose weather-tolerant cultivars
In drought conditions, shorter plants with less biomass will often produce higher yields, Palmier says. Growers in the Brown Soil Zone will often choose mid- to early-maturity cultivars that can beat the heat on flowering, MacKinnon says. When selecting cultivars suitable to dry conditions, ask for advice from people in the region who see a lot of cultivars. Choose the right cultivar for each field.
4. Select fields with low herbicide carryover risk
Canola is extremely sensitive to Group 2 herbicide carryover. Areas with moisture accumulation through the previous June, July and August of 100 mm (4”) or less will be at highest risk of herbicide carryover. That risk will be even higher in areas with multiple dry years in a row. Residual herbicides need moist soils and warm temperatures for breakdown to occur within the expected time frame. In dry conditions, the two major breakdown methods – hydrolysis and microbial degradation – will slow down, which elevates the risk that these herbicides will remain active in the soil for longer. In addition to low moisture, other factors that increase the risk of residual herbicide are low organic matter and high or low pH soils. Podcast on herbicide carryover risk.
5. Follow balanced nutrition based on deeper soil tests.
MacKinnon’s advice: Pick realistic yields and fertilize accordingly. Balanced nutrition reduces crop stress and can improve results in drought conditions. Recent research from Agriculture and Agri-Food Canada shows that adequate sulphur can improve results in drought conditions. Palmier notes that an additional deeper soil test, such as 6-24”, can be particularly useful in fields with low moisture. Crops may not have taken up all applied nutrients but some of them, particularly nitrogen and sulphur, may have moved lower in the soil profile. How much fertilizer does canola need?
6. Use very low rates of seed-placed fertilizer
When seeding into dry soils, it may be best to keep all fertilizer out of the seed row. Even a small amount of fertilizer, especially fertilizer with high salts, can damage seed and seedlings in dry conditions. Higher seed-bed utilization can increase the spread between seed and fertilizer, and lower the risk from seed-placed fertilizer, but these high disturbance openers also dry out the soil. Right rates for seed-placed fertilizer
7. Consider a split fertilizer application
Applying the full rate of fertilizer at the time of seeding is the simplest approach. However, in drier that normal conditions, growers could reduce their economic risk with a fertilizer rate appropriate for the lower yield target. They could top up with an in-season application if rains improve the yield outlook.
8. Seed to achieve the recommended plant stand
The recommended range is five to eight plants per square foot. The lower end of the range may be appropriate in dry conditions, but consider that dry conditions may lower germination rates and seedling survival. With stands below five plants per square foot, plants will produce more branches to fill the space. Side branches mature later and can delay dry-down. MacKinnon adds that waiting for thin stands to fill out will mean more bare ground for weeds. Higher seeding rate is part of an integrated weed management program.
9. Seed at around 1” depth
Placing canola at 1” depth is still recommended in dry conditions. Seeding at 1″ into dry ground and waiting for rain can be lower risk than seeding deep to chase moisture. Going much deeper than 1.5” can result in lower vigour, delayed emergence, uneven stands and more flea beetle susceptibility. And with deep seeding, rains, when they do come, can fill in the furrows and make seed depth even deeper. Rains can also cause crusting of heavier soils; crusting is a bigger challenge for deep-seeded seedlings with low vigour. If seeding to reach moisture, place seed at the top of the moisture and pack well to prevent further moisture loss.
10. Keep other stress to a minimum
Protect young canola from cutworms and flea beetles, especially if germination is delayed. Seed treatment protection only lasts so long. In dry growing conditions, consider a flea beetle action threshold lower than the normal 25 per cent defoliation. Remove weed competition while the crop struggles to establish.
