Timing of nitrogen for canola grown in the high rainfall areas of WA, Gibson 2014 trial report

Page last updated: Thursday, 18 April 2019 - 4:53pm

Previous experience with canola has found there is no yield penalty if nitrogen is applied within eight weeks of sowing and most farmers aim to apply nitrogen within this timeframe. However in high rainfall zones there have been requests from growers to investigate if canola continues to respond to nitrogen applied later than eight weeks.

Summary

  • Canola grain yield and gross margins were more dependent on nitrogen rates than the application timings.
  • Delaying application of nitrogen after eight weeks reduced canola yield. The reduction was greater the higher the proportion of total applied N delayed.
  • Hyola 404RR produced significantly higher grain yield and oil than ATR Wahoo, but similar gross margins.

Aim

To investigate the effect of nitrogen rates and time of application on grain yield, oil and gross margins of Roundup Ready and Triazine Tolerant canola.

Trial details

Table 1 Trial details
Property Esperance Downs Research Station, Gibson
Agzone 6 growing deason rainfall (GSR) 433mm
Soil type Loamy sand (1.42% organic carbon)
Paddock rotation 2013 - wheat, 2012 - sub clover, 2011 - sub clover
Sowing date 9 May
Seeding rate Target density 40 plants/m2
Fertiliser (kg/ha) 100kg/ha of Superphosphate at seeding, 120kg/ha of Muriate of Potash and 400kg/ha of gypsum (17% Ca, 14% S) top-dressed over whole site four weeks after seeding, 1L 0.7kg Zn/ha and 0.5kg Mn/ha Twin Zink and Mantrac sprayed over the whole trial six weeks after seeding

Treatment details

28 treatments

  • Two cultivars: ATR Wahoo (Triazine Tolerant open-pollinated variety) and Hyola 404RR (Roundup Ready hybrid variety) x 14 N treatments (kg N/ha) with timing spread between seeding, eight, 12 and and up to 14 weeks after sowing (Table 1).
  • Trial design: Split plot design with herbicide tolerant varieties as main plots and nitrogen rates and timings randomised within these, sown in three banks.
  • Replications: Three
Table 2 Treatment details (WAS = weeks after seeding)
No. Total N N Splitting N Treatment name Seeding 8WAS 12WAS 14WAS
1 0 Nil 0N 0 0 0 0
2 50 Seeding and 8WAS 15N 35N 15 35 0 0
3 75 Seeding and 8WAS 15N 60N 15 60 0 0
4 100 Seeding and 8WAS 15N 85N 15 85 0 0
5 125 Seeding and 8WAS 15N 110N 15 110 0 0
6 50 Two-way split 15N 10N 25N 15 10 25 0
7 75 Two-way split 15N 35N 25N 15 35 25 0
8 100 Two-way split 15N 35N 50N 15 35 50 0
9 100 Two-way split 15N 30N 25N 15 60 25 0
10 100 Three-way split 15N 60N 0N 25N 15 60 0 25
11 100 Three-way split 15N 35N 25N 25N 15 35 25 25
12 125 Two-way split 15N 85N 25N 15 85 25 0
13 125 Three-way split 15N 85N 0N 25N 15 85 0 25
14 125 Three-way split 15N 35N 50N 25N 15 35 50 25

Assumptions used in gross margins

Oil bonus: +/- 1.5% per unit of oil (%) either side of 42%, with no oil ceiling.

Additional costs: Seeding, harvest, insecticides assumed to be $180/ha.

Nitrogen costs: $1/kg (as urea) at seeding and $1.53/L ( as urea ammomonium nitrate [UAN]) at eight, 12 and 14WAS: application costs $8/ha per application.

RR costs: Seed $98/ha, herbicides $45/ha.

RR price: Grain worth $513/t (decile 5).

TT costs: Seed $40/ha, herbicides $60/ha.

TT price: Grain worth $535/t (decile 5).

Results

Grain yield

Grain yield of canola increased significantly with applied nitrogen and achieved the highest yield of 2.4t/ha at 125kg/ha (Figure 1). The grain yield of Hyola 404RR was on average 315kg/ha higher to ATR Wahoo, and Hyola 404RR produced higher yield than ATR Wahoo at all levels of applied nitrogen.

Delaying some of the nitrogen application after eight weeks reduced the canola yield and the penalty was greater the higher the proportion of total N that was delayed.  For example, a significant yield reduction of 173kg/ha was observed when 125kg N/ha was applied as a three-way split applied (50kg within eight weeks, 50kg/ha at 12 weeks and 25kg/ha at 14 weeks after seeding) compared to the treatment which applied all of the nitrogen within eight weeks of seeding (Figure 2).

Grain oil concentration

Generally increasing rates of nitrogen resulted in a decline in oil concentration of canola with the lowest concentration found at 125kg/ha (Figure 1). Delaying nitrogen application tended to reduce oil (Figure 3).

Varieties differed significantly in their oil concentration with Hyola 404RR containing 48.6% compared to ATR Wahoo with 46.8%.

Gross margins

Canola gross margins began to plateau at 50kg N/ha (Figure 1). Thus application of 50kg/ha nitrogen within eight weeks of seeding produced higher gross margins than the nil treatment but statistically similar gross margins to all other the treatments.

On occasions delaying nitrogen application reduced gross margins. For example, when 75kg N/ha was split applied at 12 weeks after seeding gross margins were reduced by $98/ha compared to applying 75N within eight weeks. Similarly when 125kg N/ha was applied in a three-way split (50kg within eight weeks, 50kg/ha at 12 weeks and 25kg/ha at 14 weeks after seeding) a reduction of $125/ha was observed compared to applying all of the nitrogen within eight weeks of seeding (Figure 4 and 5).

On average Hyola 404RR produced similar gross margins than ATR Wahoo.

Grain yield of canola increased significantly with applied nitrogen and achieved the highest yield of 2.4 t/ha at 125 kg/ha
Figure 1 Effect of nitrogen fertiliser rate on grain yield, gross margin and oil concentration of canola at EDRS Gibson in 2014. LSD (P<0.05): grain yield = 119 kg/ha; gross margin = $69/ha; oil = 0.47%
Delaying some of the nitrogen application after 8 weeks reduced canola yield and the penalty was greater the higher the proportion of total N that was delayed
Figure 2 Effect of nitrogen treatments on the grain yield (kg/ha) of canola at EDRS Gibson in 2014. LSD (P<0.05) = 160 kg/ha. N treatment – N (kg/ha) applied at 0 (seeding), 8, 12 and 16 weeks after seeding, respectively
Delaying nitrogen application tended to reduce oil
Figure 3 Effect of nitrogen treatments on the oil concentration (%) of canola at EDRS Gibson in 2014. LSD (P<0.05) = 0.64%. N treatment – N (kg/ha) applied at 0 (seeding), 8, 12 and 16 weeks after seeding, respectively
On occasions delaying nitrogen application reduced gross margins
Figure 4 Effect of nitrogen treatments on the gross margins ($/ha) of canola at EDRS Gibson in 2014. LSD (P<0.05) = $88/ha. N treatment – N (kg/ha) applied at 0 (seeding), 8, 12 and 16 weeks after seeding, respectively
Effect of nitrogen treatments on the gross margins
Figure 5 Effect of nitrogen fertiliser rate and split applications on the gross margins ($/ha) of canola at EDRS Gibson in 2014. LSD (P<0.05) = $75/ha

Conclusion

Delaying some of the nitrogen application beyond eight weeks after seeding to 12 or 14 weeks did not lead to yield or gross margin benefits. Instead there was a tendency of declining yield and gross margins; and generally the penalties were greater higher the proportion of total N that was delayed.

Acknowledgements

This trial (14ED13) is one of a series conducted throughout Western Australia as part of the GRDC/DPIRD co-funded project Tactical Break Crop Agronomy in Western Australia. The help from Pam Burgess in conducting this trial is greatly appreciated and acknowledged. Thanks to EDRS Gibson for hosting the trial and to the Esperance RSU for trial management.

Contact information

Raj Malik
+61 (0)8 9821 3247