Canola yield penalty with delayed sowing

How late is too late to sow canola? What is the yield penalty from time of sowing (TOS) or late sowing? What is the estimated yield loss from delayed sowing of canola in WA? Department of Agriculture and Food, Western Australia (DAFWA) research officers have used two methods to address these questions;

1. Yield loss from delayed sowing trials in WA.

2. Yield loss estimated by APSIM modelling for Kojonup, Esperance, Wongan Hills, Newdegate, Mingenew, Merredin and Mullewa.

1. Yield loss from delayed sowing trials in Western Australia

DAFWA development officer Jackie Bucat has compiled data from, and summarised, time of sowing trials for canola in WA (Figure 1).

There are variable yields and variable loss profiles for the start of May.

However, from mid-May onwards, there is a generally a similar rate of loss across most trials.

Overall, the yield loss from delayed sowing is about 15kg/ha/day for the third week of May, up to a peak of 25kg/ha/day for the first half of June.

In general, growers could expect to lose more than half a tonne of yield if sowing is delayed from mid-May to mid-June.

A decrease in oil percent would also be expected, with later sowing time.

Table 1 Canola yield penalty with delayed sowing, from WA trials
  Average loss per day (kg/ha) Average loss per week (kg/ha)
Third week in May 10 70
Fourth week in May 15 105
First week in June 25 175
Second week in June 25 175
Third week in June 20 40

Similar rate of loss after mid-May from trials at Merredin, Mullewa, Mt barker, Wongan Hills, Beverley and East Chapman
Figure 1 Canola yield decline with delayed sowing, data from WA trials

2. APSIM modelling estimates of yield loss for different locations

Localised differences in expected yield and estimated yield loss rates can be shown by computer modelling. DAFWA research officers Bob French and Imma Farre have used Agricultural Production Systems Simulator (APSIM) to model canola yield decline with later time of sowing, for seven locations.

The modelling was done using 2017 rainfall, up until 24 May, then the ongoing rainfall for each of the last 40 seasons. The median results are presented in Figure 2.

These results give an estimation of expected yields, as well as the rate of loss. Differences in the rate of loss between environments is shown, with later peak yield loss in longer season environments (Table 2). During the period 10-20 May, yield losses may be around are 8kg/ha/day at Kojonup but 36kg/ha/day at Mullewa.

If sowing is delayed from 10 May until the end of May, APSIM estimated a cumulative 46% yield loss at Mullewa, but only 9% at Kojonup (Table 3).

Highest yields at Kojonup, followed by Gibson, Wongan Hills, Newdegate, Mingenew, Merredin and Mullewa.
WA canola yield with delayed sowing, modelled with APSIM, with 2017 rainfall up to 20th May, and median result of last 40 seasons after 20th May

APSIM modelling included predicted losses to frost and heat. Variety used for APSIM was ATR Bonito (Kojonup, Esperance, Wongan Hills, Merredin) and Hyola 404 (Mullewa). Single soil type used (shallow sandy duplex).

Table 2 APSIM modeled yield loss (kg/ha/day) for sowing delayed from 10 May
Sowing Kojonup Gibson Wongan Hills Newdegate Mingenew Merredin Mullewa
20 May 8 5 25 15 28 29 36
30 May 13 21 30 23 30 22 30
9 June 23 16 27 24 36 21 21
19 June 30 27 19 23 27 11 18
29 June 25 28 25 19 16 23 12
Table 3 Cumulative yield loss (%) when sowing delayed from 10 May, as modelled with APSIM
Sowing Kojonup Esperance Wongan Hills Newdegate Mingenew Merredin Mullewa
20 May 3 2 13 8 16 19 26
30 May 9 12 27 21 32 33 46
9 June 18 19 41 34 52 46 61
19 June 31 31 51 47 67 53 74
29 June 41 43 63 57 76 68 82

How late is too late to sow canola?

Answering this question depends on;

  • Stored soil moisture - 2017 rainfall included in the APSIM modelling
  • On-time yield estimate - best to use average from past ‘normal’ seasons
  • Estimated yield loss - as suggested above, balanced with your experience
  • Break even yield - essential to know this to make an informed decision
  • End of season conditions - much will depend on finishing rains.

Options when considering dropping a canola paddock


If plans were to grow canola as a valuable break crop in your rotation, the best decision may be to go ahead, albeit with a lower profit estimate, to capture the disease/weed control rotation benefit. Minimise inputs and delay nitrogen top up until early flowering, when a better seasonal assessment can be made.


If there is disease or weed pressure building up in the paddock, beware of substituting a cereal crop as the paddock might end up in a worse position for the start of the 2018 season.


Field pea may be a good option for later sowing on heavier soil types, but access to seed and high seed prices make this an unlikely option.


Leaving this paddock to fallow or pasture may not have been what was planned for 2017, but will leave the paddock well set up for a more promising start in 2018. A fallow will store future moisture as well as giving a disease and weed break. Legume pastures will put the paddock ahead for nitrogen in 2018 and topping any pasture will put the paddock ahead for weed control.

Contact information

Page last updated: Wednesday, 31 May 2017 - 9:10am


Jackie Bucat
Bob French