Canola establishment across central NSW

Take home messages

  • Across 95 paddocks within the low, medium and high rainfall zones of central NSW, the  average canola establishment was 48%, and ranged from 17% to 86%.
  • Seed size was the main differentiating factor that improved canola establishment.
  • Other key agronomic factors for improved canola establishment were stubble removal, reduced sowing speed, shallow seed placement and phosphorus (P) fertiliser separated from the seed.
  • Hybrid (H) varieties were generally larger in size, and establishment was better than open-pollinated (OP) varieties.

Background

Canola establishment has become an emerging issue within central NSW over the past decade, due to increased seed costs, reduced seeding rates, unreliable autumn rainfall and sowing into marginal seedbed conditions.

Canola seed costs from 1990 to 2010 were relatively stable at 4% of total input costs, and have since increased to 14% of total input costs in 2018 (NSW DPI crop budgets). The increased seed cost is largely related to the dominance of H varieties over OP varieties since 2011 to 2018 (Figure 1). Target plant density during the era that OP varieties dominated the market place (pre-2010) was 50–80 plants m2 (Wurst et al. 1997) and seeding rates between 3–5kg/ha. However, since the adoption of hybrids, the target plant density has been reduced to approx. 20–50 plants m2 (Zhang et al. 2016, Matthews et al. 2018) depending on rainfall zone. Currently, best management practice is to firstly determine target plant density (plants m2) for your rainfall region, and then determine seeding rates via knowledge of seed size, germination percentage (%) and estimate of establishment %.

Recent developments in understanding variety phenology, sowing time, and the adoption of slower developing spring varieties have brought forward the sowing window from 25 April to early April (Brill et al. 2018) for slower developing spring types. This broader, more flexible sowing window enables canola establishment to occur when seasonal conditions allow (i.e. rainfall events), rather than wait for the traditional Anzac Day trigger point to initiate sowing. This greatly improves the flexibility of the farming system, however, establishing canola in early April has the disadvantage of high seedbed moisture dry-back due to greater evaporation demands caused by higher temperatures. For example, at Parkes (medium rainfall zone), the average daily evaporation reduces from 5.9mm, 3.7mm to 2.2mm across the respective months of March, April and May (Figure 2). This means that a shallow planted canola seed is at higher risk of seedbed moisture dry-back if sown in early April compared to May, particularly in the warmer regions of NSW (i.e. Condobolin).

In summary, the margin for error in establishing canola is small, we are now sowing less seeds, they are costing more money, and we are placing those seeds in higher moisture dry-back conditions.  Successful canola establishment is a significant factor, and a risk in canola production. The primary purpose of this survey was to evaluate current canola establishment rates and uniformity of plant spacings. The secondary purpose of the survey was to evaluate management practices that affect canola establishment, such as stubble management, seeding systems, fertiliser and seed quality.

Figure 1. Year release of H or OP canola varieties in Australia from 1978 to 2017 (Source: Steve Marcroft).

Figure 2. Average daily evaporation rates across central NSW during March, April and May (Source: CliMate).

Method

A field survey was conducted in 2017 across 95 commercial paddocks within the low, medium and high rainfall zones of central NSW (approx. 30 paddocks from each rainfall zone). Paddocks were selected from the following localities — Tottenham, Tullamore, Trundle, Condobolin, Bogan Gate, Parkes, Forbes, Marsden, Manildra, Cowra, Young, Boorowa and Jugiong.

Paddocks were selected to include various combinations of stubble management (burnt, retained and cultivated) and seeding system (knifepoint /presswheel, disc or scatter-plate). The survey design allowed for 10 paddocks with each combination of stubble management and seeding system from each rainfall zone (low, medium and high).

Plant establishment was measured across 15 x 1m2 quadrants per paddock, and from this an establishment % was determined via knowledge of seed size and sowing rate. If the seed size was unknown, a sample was taken for seed size determination. Plant population and plant uniformity were measured via the development of the ’vacancy %’ method. This method relies on using a 1m2 section of mesh with 10cm squares. The mesh is used as the quadrant to count plants across 4 x 1m linear rows, as well as to count the total number of vacant squares within four linear metres. From this plant population and a vacancy % were determined.

Other data collected from each paddock includes sowing date, seeding depth, fertiliser rate/placement/source, variety, seeding rate, GPS coordinates, seed treatment, sowing speed, soil type, seedbed moisture conditions at sowing, and crusting events post sowing.

Results and discussion

A wet March and some timely rainfall events in April (Figure 3) allowed canola to be sown into favourable seedbed conditions across the low, medium and high rainfall zones of central NSW in 2017. March rainfall was above the long-term average (LTA) at Condobolin, Parkes and Cowra, with an additional 41mm, 56mm and 49mm above the LTA, respectively. Seedbed moisture conditions were favourable at the start of April, and then started to decline from mid-April onwards. Additional rainfall around Anzac Day ensured favourable crop establishment for most of central NSW. In the paddock survey, the earliest, median and last sowing dates were 10 April, 22 April and 10 May, respectively.

Figure 3. Daily autumn rainfall events across Condobolin, Parkes and Cowra in 2017.

Across the 95 survey paddocks, 44 were hybrid varieties and 51 were OP (Table 1). Breeding type (H or OP) was largely influenced by growing season rainfall and length of growing season, with H varieties dominating the high rainfall zone (22 H, 1 OP), OP dominating the low rainfall zone (4 H, 28 OP), and an even split between H and OP in the medium rainfall zone (H 18, OP 22). Refer to Table 1 for further details

Table 1. Breeding type and herbicide tolerance of paddocks surveyed across the low, medium and high rainfall zones of central NSW in 2017.

Breeding type

Rainfall region

Total
LowMedHigh

Hybrid

4182244

Clearfield®

19717

Conventional

34 7

Roundup Ready®

 224

Roundup Ready® + Triazine Tolerant

  22

Triazine Tolerant

 31114

OP

2822151

Triazine Tolerant

2822151
 32402395

Across the 51 survey paddocks that were OP, 16 paddocks were purchased seed and 35 paddocks were grower retained seed. Interestingly, only four of the 35 grower retained seed paddocks were not graded to seed size. Seed size grading ranged from 1.6mm to 2mm sieve size, however the sieve size was determined by the ratio of total seed graded to how much seed was required for the following sowing.

Interestingly, across all paddocks the average seeding rate was 2.5kg/ha for OP (1.6–4kg/ha), and 2.4kg/ha for H (0.9–3.2kg/ha). The average seed size from the H varieties was 4.9g/1000 seed (203,610 seeds/kg), and 3.9g/1000 seeds (257,106 seeds/kg) for the OP.

Table 2 illustrates a summary of results for establishment %, plant density and vacancy %. The average establishment was 48%, and the majority (between 1st and 3rd Quartile) of paddocks ranged between 38% and 58%. Establishment improved from low to medium to the higher rainfall zone, with the low, medium and high rainfall zones achieving a respective 43%, 47% and 55% establishment.

Table 2. Establishment, plant density and vacancy % on 95 paddocks surveyed in central NSW in 2017.

Frequency

Establishment (%)

Plants density

(m2)

Vacancy

(%)

Min17%1076%

1st Quartile

38%1956%
Mean48%2647%

3rd Quartile

58%3239%
Max86%6418%

While each paddock had 36 pieces of information recorded, the main factor that differentiated establishment % was seed size. The mean seed size was 4.3g/1000 seeds and ranged from 3.3g to 6.6g/1000 seeds.

Figure 4 shows that establishment improved as seed size increased, however this trend was not linear and establishment decreased between the seed size of 4g and 4.5g/1000. In addition to seed size, there was an average increase in establishment by 6% (points) from selecting an H seed over an OP seed (51% establishment for H, and 45% establishment for OP).

After seed size, the top four agronomic practices that influenced canola establishment were seeding system (P=0.01), stubble management (P=0.02), sowing speed (P=0.02) and P fertiliser placement (P=0.05).

On average, reducing stubble loads via either burning or cultivation improved canola establishment by 10% (Figure 5). The main benefit appears to be from the physical removal of the stubble, rather than cultivated seedbed.

Table 2 shows that the average vacancy % was 47%, and ranged from 18% to 76%. Further research trials are being undertaken to develop calibration relationships between vacancy % and grain yield.

Figure 4. Fitted and observed relationship between seed size (g/1000 seeds) and canola establishment % with 95% confidence intervals.

Figure 5. Effect of stubble management, seeding system, sowing speed and fertiliser placement on canola crop establishment. Standard error bars shown.

Interestingly, old seeding system technology such as ’scatter-plates’ performed well in this survey. On average, the highest establishment of 58% was achieved with scatter-plates, and then reduced to 49% and 41% with the respective knifepoint and disc machine seeding systems. It is likely that the main benefits of the scatter-plate seeding system are due to shallow seed placement and favourable autumn conditions in 2017.

Establishment decreased as sowing speed increased, with a 16% establishment reduction if speed increased from 6–8km/hr to 13–17km/hr.

On average, there was a 7% reduction in establishment if P fertiliser was not separated from seed. There were two main groups of P fertiliser rates — 40% of paddocks had between 50–75kg/ha monoammonium phosphate (MAP) and another 40% had between 75–100kg/ha MAP.

Conclusion

Despite favourable sowing conditions in 2017, these results suggest there is an opportunity for improved canola establishment in central NSW. Effectively, growers are only establishing half of what they purchase, and if the autumn break was less favourable, it is likely to be much less. Traditionally, growers would apply an extra 1–1.5kg/ha of seed to compensate for poor sowing conditions, however this is no longer an option given the associated higher costs with hybrid seed.

Seed size was the main differentiating factor that improved canola establishment, while the other key agronomic practices were stubble removal, reduced sowing speed, shallow seed placement and P fertiliser separated from the seed. Hybrids were generally larger in size, and establishment was better than OP varieties. Further research is required to evaluate why the relationship between seed size and establishment was not linear.

The benefits of the scatter-plate seeding system in 2017 were likely to be associated with shallow seed placement combined with weather conditions that provided moist conditions for the canola seedling to germinate and establish. Canola establishment results are likely to be different if moisture seeking was required. These results highlight the importance of taking time to set up seeding equipment, particularly with the disc seeding machine as they are typically used in high stubble load paddocks, sowing speeds are higher and have limited fertiliser separation from the seed.

References

Brill, R., Menz, I., Reardon, D., Malcolm, D., McCaffery, D., McMaster, C., Kirkegaard, J. and Lilley, J. 2018: Canola – well executed agronomy still makes a difference in 2017. Wagga Wagga GRDC Update (https://grdc.com.au/resources-and-publications/grdc-update-papers/tab-content/grdc-update-papers/2018/02/canola-well-executed-agronomy-still-makes-a-difference-in-a-tough-2017)

Matthews, P., McCaffery, D. and Jenkins, L. 2018: Winter crop variety sowing guide 2018. NSW Department of Primary Industries, p71.

Wurst, M., Cummins, J. and Stanley M. 1997: TOPCROP Crop monitoring guide 1997-1998. PISA Clare, p48.

Zhang, H., Berger, J., Seymour, R., Brill, R., Herrmann, C., Quinlan, R. and Knell, G. 2016: Relative yield and profit of Australian hybrid compared with open-pollinated canola is largely determined by growing season rainfall. Crop & Pasture Science, 67, 323-331.

Acknowledgements

The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC – the author would like to thank them for their continued support.

This survey was part of the project ‘Improved canola establishment’, BLG110, 2017, a joint investment by GRDC and NSW DPI under the Grains Agronomy and Pathology Partnership (GAPP). The authors would also like to acknowledge the assistance of Justin Paul, Paula Charnock and Daryl Reardon in conducting the field survey, Jennifer Pumper for seed size testing and the growers and advisers who provided paddocks within central NSW.

Contact details

Colin McMaster
161 Kite Street, Orange NSW, 2800
0427 940 847
colin.mcmaster@dpi.nsw.gov.au
@master4colin

GRDC Project Code: BLG110,