Background
Sowing canola in mid-April has become standard practice in the far north of the WA cropping zone. However, there is little research data on the effect of these sowing dates on yield. The Tactical Break Crop Agronomy team took advantage of early sowing opportunities in 2015 and 2016 to sow trials early and fill this knowledge gap.
Method
Two trials were undertaken which tested a range of canola varieties sown at two different sowing dates (TOS 1 and TOS 2). In 2015 a trial was sown at Binnu on April 15 and April 29. In 2016 very early sowing occurred at Wongan Hills on March 31 and April 15 (Figure 1)..
At Binnu there were 10 varieties (5 TT and 5 RR); CB Telfer (very early), Stingray (early), Bonito (early/mid), Hyola® 450TT (mid), Hyola® 559 (mid/late), Pioneer 43Y23 (early), Hyola® 404 (early/mid), GT41(early/mid) GT50 (mid), Hyola® 525 (mid)
At Wongan there were 6 varieties; all were Round-up Ready hybrid plant types; Pioneer 43Y23 (early), Hyola® 404RR (early/mid), GT50 (mid), Hyola® 525RT (mid/late), Hyola 600RR (late), Hyola® 725RT (very late).
Results
Yield Binnu
The overall yield of the trial was 1322 kg/ha. Averaged across all varieties TOS 1 yielded 1647 kg/ha compared to TOS 2 997 kg/ha. Hence 650 kg/ha less yield from delaying sowing by 15 days, a loss of 43 kg/ha/day. There was a variety response (P<0.001) with the more recently released hybrids among the highest yielding varieties.
There was no significant difference between the varieties in their response to sowing time. Round-up Ready types yielded 1362kg/ha on average and triazine tolerant types yielded 1282kg/ha (Figure 2).
Yield Wongan Hills
The overall yield of the trial was 2755kg/ha. Canola sown on March 31 yielded 2853kg/ha compared to 2658kg/ha for canola sown on April 15, averaged across all varieties. Hence delaying sowing by 15 days led to 195kg/ha less yield, which is equivalent to an average loss of 13kg/ha/day.
For the early varieties, Pioneer 43Y23 and Hyola® 404RR, there was no advantage toi seeding in March compared to April. For the mid-season maturity varieties, GT50 and Hyola® 525RT, yields increased by 360kg/ha (24kg/ha/day) or 11 and 12 % respectively with March sowing. For the long-season maturity varieties Hyola® 600RR and Hyola® 725RT, yields increased by around 260kg/ha from March sowing (17kg/ha/day) or 9 and 10% respectively (Figure 3).
Seed quality
For both trials there were significant differences in seed oil content between varieties but not between the sowing times.
Plant growth
In both trials, the plants that emerged earlier produced more biomass, although this response was less pronounced in the short season, smaller plant-type varieties (Figure 4).
APSIM simulation modelling comparison
The yields obtained in the Wongam Hills trial were compared to predicted yields using the APSIM model.
On average, the optimum time of sowing for Wongan Hills is simulated to be 7 April - 6 May, with lowere yields for March sowing (Figure 5).
The trial yields were close to that simulated by the model for the 2016 season. In 2016, simulated yield increased when sown in March compared to April, due to summer rain and early season rainfall. However, the model output for 2000-2015 suggests this is not common.
Conclusions
The research to date strongly indicates, if a mid-April sowing opportunity occurs growers should take it. This will maximise yield and reduce the risk of experiencing a long delay to the next sowing opportunity. Although there will be increased disease and pest risk, due to the longer period of exposure, and increased risk of adry spell after sowing.
APSIM simulations are a valuable tool in understanding and simulating (predicting) particular seasonal results.
More work is required to investigate very early sowing of canola over a wider range of years and locations.