The trial, which was undertaken as part of the GRDC funded project ‘Maintaining profitable farming systems in retained stubble’, compared the establishment of canola sown with disc and tyne seeding machinery in situations when stubble was retained and burnt, and when urea was applied at sowing.
Initial plant counts conducted on April 28 (16 days after sowing) showed that plant establishment was better where the tyne seeder has been used. This was apparent regardless of whether stubble had been retained or burnt.
Since then, and with the arrival of the season break on May 9 and 10, more canola has established in both the disc and tyne sown plots. This has mirrored the experience of local growers with advisers reporting widespread staggered canola germination which has come as a result of the dry start to sowing this year (a consequence of below average season rainfall in 2015, a dry summer, low sub-soil moisture and very little rain in April 2016).
While on April 28 (16 days after sowing), only one canola plant/m2 was recorded in the disc-sown, stubble retained treatment, on May 19 (5 weeks after sowing) 12 canola plants/m2 had emerged. Meanwhile, in disc-sown burnt treatment plant numbers rose from three plants/m2 on April 28 to 20 plants/m2 on May 19.
Where the tyne seeder was used plant counts remained unchanged where stubble had been retained and increased slightly where stubble was burnt.
To examine the effect of nitrogen application on crop emergence, growth and yield, urea was applied to half of each plot at sowing at a rate of 60kg/ha.
The application of urea at sowing had very little effect on crop establishment where the disc seeder had been used, regardless of whether stubble had been retained or burnt. This result was unexpected with urea thought to reduce emergence in a dry sowing situation.
In the tyne-sown plots, however, plant numbers dropped by six plants/m2 in both retained stubble and burnt situations when urea was applied at sowing. This was despite the urea being place under the seed to minimise the impact (Figure 1).
To examine the impact of post sowing baiting for insects and slugs, Mesurol at 2.5kg/ha and Metarex at 8kg/ha was applied as 3 x 10 metre wide bands across the trial site. The reduction in plant numbers was very noticeable in the unbaited areas, particularly in the stubble retained plots.
In the disc-sown, stubble retained plots plant numbers dropped from 12 plants/m2 down to two plants/m2, while in the burnt treatments no bait reduced emergence by five plants/m2.
Where bait was applied in the tyne-sown plots, emergence was six plants/m2 higher in the stubble retained treatments and four plants/m2 in the burnt treatments (Figure 2).
Tiles were placed in each treatment immediately after sowing to assess slug, millipede and earwig populations. Millipedes were present in high numbers and the seedlings suffered serious damage. The whole site was treated with an insecticide applied on May 12 (sprayed at night to maximise efficacy). Counts after spraying indicate reasonable control but there are still low levels of millipedes alive (Figure 3).
The work thus far has highlighted the many challenges faced when establishing canola in the Western District. Follow progress on the research via the SFS website or https://thestubbleproject.wordpress.com/.
This article was published in the Stock and Land on June 9.