For optimum yields in the Northern grains region, canola needs to be sown in the period from mid-late April to mid-May. While it is generally accepted that canola establishes best when sown into a moist seedbed at a depth of about 2 cm, such conditions are rarely available in cropping zones of the Northern grains region. In 2012 a trial, utilizing several trial sites, was conducted across Northern NSW to investigate the effect of sowing depth, fertiliser rate and retained stubble on the establishment of several hybrid and open pollinated canola varieties. In addition to the field trials a glasshouse trial conducted at Tamworth was designed to determine if any establishment differences were due to variety choice, plant type (hybrid vs O.P.) or seed size.

Several consistent messages emerged from the trials resulting in the general recommendation of a planting depth of 2.5 cm for canola where conditions allow.

However, these trials also show that where the soil surface is dry but moisture is available below 2.5cm, it is possible to establish a commercially acceptable population by sowing deeper. Pioneer® brand 44Y84 (CL), which was included in the trial, was a standout variety and also had the largest seed of all the varieties sown, overall hybrids in general had higher establishment than open-pollinated lines.

Averaged across all trials and varieties, establishment at the 2.5 cm seeding depth was approximately 66%. With the exception of 44Y84 (CL), all varieties had significantly reduced establishment at the 5 cm sowing depth compared to the 2.5 cm sowing depth.

All varieties had significantly reduced establishment at the 5 cm sowing depth compared to the 2.5 cm sowing depth, with the exception of Pioneer 44Y84 (CL).

Increasing the sowing depth from 5 cm to 7.5 cm resulted in the lowest establishment for all varieties, reducing establishment by an average of 81% compared with the 2.5 cm sowing depth. Significantly though, 44Y84 (CL) had higher establishment than all other varieties at the deepest sowing rate (7.5 cm). 44Y84 (CL) established on average 16 plants/m² at the 7.5 cm sowing depth, compared with Pioneer® brand 43C80 (CL), ATR-Gem and AV-Garnet which established 3, 5 and 6 plants/m², respectively.

There was no consistent yield reduction when sowing depth was increased from 2.5 cm to 5 cm; however the yield loss at the 7.5 cm sowing depth compared with the 2.5 cm sowing depth was 0.35 t/ha, averaged across all varieties. 44Y84 (CL) was on average the highest yielding variety, with an average yield of 1.5 t/ha. This compares with the next best lines, Hyola 50 and Hyola 555TT, which averaged 1.2 t/ha. 43C80 (CL) and ATR Gem had an average yield of 0.8 t/ha.

Figure 1: Establishment of six canola varieties at three sowing depths, averaged across three trials at Coonamble, Nyngan and Trangie in 2012

Figure 2: Establishment of six canola varieties sown at three sowing depths, averaged across two trials at Moree and Blackville in 2012

 

Increasing the phosphorus rate (as triple super in these trials) can also reduce establishment of canola, therefore it could be assumed that the combination of both deep sowing and high fertiliser rates would have a greater effect on establishment, however further trials will need to investigate this. Retained stubble, especially heavy stubble loads, were shown to be an additive effect and will reduce establishment regardless of sowing depth.

The effect of deep sowing on grain yield  is much less pronounced than it’s impact on establishment, therefore deeper sowing could be worth considering to ensure timely canola establishment.

The effect of deep sowing on grain yield is much less pronounced than it’s impact on establishment, therefore deeper sowing could be worth considering to ensure timely canola establishment.

Across all trials, yield results from hybrids were generally greater than the open-pollinated lines. 44Y84 (CL) was the highest yielding line in the trials where it was included and Pioneer® brand 43Y85 (CL) was the highest yielding line when 44Y84 (CL) was not included.

Summary

Aim to sow canola to target 20-25 plants/m² in the Northern grain regions and western NSW, adjusting sowing rate based on seed size. Where seed needs to be placed deeper than optimum seeding depths (deeper than 2.5 cm), ensure that the seed is large (greater than 5 g/100 seeds) and that high rates of fertiliser in contact with the seed are avoided. High stubble loads will reduce establishment at all sowing depths. Hybrids had significant farming system (establishment and vigour) and yield benefits in the trials conducted in 2012.

 

  • Planting canola deeper than 2.5 cm reduced overall establishment in 2012; however grain yield was generally affected to a smaller degree.
  • Where planting into moisture below the optimum seeding depth (>2.5 cm), use large seed (minimum 5 g per 1000 seeds), avoid high rates of fertiliser in direct contact with the seed and avoid high stubble loads.
  • Hybrids generally have larger seed than open pollinated varieties. Relatively large seed will generally have better establishment than relatively small seed.
  • Seeding rates should be based on target plant population and seed size rather than applying a blanket sowing rate (in kg/ha), particularly given the large differences in seed size between varieties.
  • In 2012 trials, hybrids generally displayed yield and farming system benefits over open pollinated varieties.

 

Acknowledgements

Rohan Brill¹, Matthew Gardner², Leigh Jenkins³ and Tim McNee4

¹NSW DPI Coonamble, ²NSW DPI Tamworth, ³NSW DPI Warren, 4NSW DPI Nyngan

The farmer co-operators: the Dixon family, ‘Gilgi’ Coonamble; the Wass family, ‘The Plains’ Nyngan; Paul and Charles Tattum, ‘Bonniedoon’ Moree; Joe Fleming, ‘Parraweena’ Blackville is gratefully acknowledged.

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– See more at: http://www.grdc.com.au/Research-and-Development/GRDC-Update-Papers/2013/02/Canola-establishment-effect-of-variety-choice-seeding-depth-and-phosphorus-rate#sthash.okg5gBCj.dpuf