Kirk: Response of Canola to Low Plant Populations and Evaluation of Reseeding Options
Date: July 2010
Term: 3 years
Status: Completed
Researcher(s): Anne Kirk and Blaine Davey, Western Applied Research Corporation, Sherrilyn Phelps, Saskatchewan Ministry of Agriculture, North Battleford, SK, Eric Johnson, Agriculture and Agri-Food Canada, Scott, SK, Steve Shirtliffe, Department of Plant Sciences, University of Saskatchewan, Cecil Vera, Agriculture and Agri-Food Canada, Melfort, SK, Chris Holzapfel, Indian Head Agricultural Research Foundation, Indian Head, SK and Bryan Nybo, Wheatland Conservation Area, Inc., Swift Current, SK
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: SCIC
Project Summary
Researchers in Saskatchewan initiated a three-year project in 2010 to try to answer the question of how producers could respond when faced with low plant populations in hybrid canola due to poor stand establishment, spring frost, or pest damage. Although hybrid canola is able to compensate for low plant populations, knowing the yield response to low plant populations would assist producers with decisions for reseeding. Overall, the study found that with a plant stand of 20 plants/m2 or less, reseeding in early June to hybrid canola provides a yield and economic benefit compared to leaving the stand of low-density canola. However, if conditions do not allow for reseeding to occur in late May or early June, producers are not recommended to reseed to canola.
Although there have been numerous studies looking at canola seeding rates, there is limited data on the response of canola, particularly hybrids, to extremely low plant populations. Although hybrid canola is able to compensate for low plant populations, producers need to know when the plant population is likely too low to compensate for the reduced plant stand. This is particularly important when producers are faced with reseeding decisions in the spring because of losses due to frost, wind, pests or other factors.
Researchers in Saskatchewan initiated a three-year project in 2010 to update the research on low plant populations in hybrid canola. The objectives of this project were to determine: the plant population when canola hybrids yield 90% of maximum; the effect of plant population on maturity, seed size and green seed; the minimum plant density at which hybrid canola should be reseeded; and the risks with each reseeding option in terms of maturity, yield and quality.
Field experiments were conducted across a range of growing conditions at Indian Head, Melfort, Saskatoon, Scott and Swift Current, Saskatchewan in 2010, 2011 and 2012. Canola was seeded at rates of 5, 10, 20, 40, 80, 150 and 300 seeds/m2 to evaluate the response of hybrid canola to low plant densities. The rate of 150 seeds/m2 is considered to be a standard seeding rate and was used as the check for comparison. Plots were fertilized to soil test recommendations and registered herbicides, insecticides and fungicides were applied as required at each site.
Two hybrid Brassica napus cultivars (5440LL and 9350RR) and one variety of Brassica rapa were reseeded into existing stands of low density canola in early and mid-June to evaluate reseeding options. Data collection included spring plant density, days to start and end of flowering, days to maturity, lodging index, grain yield, thousand kernel weight, percent distinctly green seed and fall plant density.
The results across all of the experiments showed that canola achieved 90 % of maximum yield at a plant density of 18 plants/m2. In general, days to maturity and percent green seed increased as plant density decreased. Averaged across locations, the highest plant populations matured nine days earlier than canola at the lowest plant populations. The reseeding project also showed a delay in maturity of five days with the low plant population compared to the high plant population seeded on the same date in early May.
When plant density was reduced the canola plant was able to compensate by increasing the number of branches and pods per plant. Averaged across years and locations, the number of pods per plant increased from 150 at seeding rates of 150 and 300 seeds/m2 to 851 at a seeding rate of 5 seeds/m2. In general, the increase in pods per plant was due to increased podding on primary and secondary branches, while the number of pods on the main stem stayed about the same. However, there was no significant yield difference between the two cultivars at any seeding rate.
Results from the reseeding trials showed a yield benefit from reseeding with B. napus in early June but no yield benefit to reseeding in mid-June. There was also no advantage to reseeding with B. rapa, even when reseeding was postponed to mid-June. Reseeding in early June to hybrid canola when plant stands are at 20 plants/m2 or less, provides a yield and economic benefit compared to leaving the stand of low density canola. However, if conditions do not allow for reseeding to occur in late May or early June producers are not recommended to reseed to canola.
Figure 1. From left to right: image 1: 5 pl/m2, image 2: 20 pl/m2, image 3: 80 pl/m2, image 4: 300 pl/m2.
Source: Anne Kirk, WARC.
Table 20. Influence of reseeding canola on economic return at Indian Head, Melfort, Saskatoon, Scott and
Swift Current in 2010, 2011 and 2012.
1Costs obtained in spring 2013 from industry.
2Based on a seeding rate of 150 live seeds m-2 for all treatments. Treatment 2 was seeded at 20 seeds m-2; however, this was to mimic a situation where canola was seeded at a typical seeding rate and environmental conditions resulted in a low plant stand.
3Based on costs from custom rate guide (Saskatchewan Ministry of Agriculture 2012).
4Based on a price of $0.58 kg-1
5Includes Saskatchewan Crop Insurance Corporation (SCIC) establishment benefit of $148.20 ha-1 to help cover reseeding costs.
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