Timing of nitrogen in low rainfall canola, Chapman Valley 2014 trial report

Page last updated: Wednesday, 27 March 2019 - 10:43am

In general, as long as nitrogen is applied within eight weeks of sowing, there is no yield penalty.

How canola responds to nitrogen applied later than eight weeks has not been widely researched. Similarly how new generation canola such as RoundupReady (RR) hybrids respond to nitrogen has not been widely tested, particularly in low and medium rainfall areas.

Summary

  • Grain yield responded to applied nitrogen up to 70kg/ha.
  • Oil did not decrease as nitrogen rate increased, unlike what we have observed at other trials – probably a reflection of the continued grain yield response to N.
  • Positive gross margin returns were seen at 40-70kg/ha of applied nitrogen.
  • Overall when nitrogen was applied did not alter the response to nitrogen – but avoid putting the majority of N at 12 weeks.

Aim

To investigate the response to changing the nitrogen rate and changing the time of application. Canola yield and oil will be measured and RR hybrids will be compared with open-pollinated TT types (OP TT).

Trial details

Table 1 Trial details
Property Narra Tarra Moonyoonooka Road, Narra Tarra
Growing season rainfall (GSR, April to October) 255mm, GSR + stored water (estimate) = 325mm. Long term average (LTA, 1974on) 371 and 418mm. Lower than LTA June, July and August, but above average September
Soil type Brown deep sand (0.72% organic carbon), estimated to be 49kg N/ha available in paddock from soil and plant residues
Paddock rotation 2013 - wheat, 2012 - wheat, 2011 - wheat
22 treatments Two cultivars (Sturt TT [TT open-pollinated variety] and Pioneer 43Y23 RR [RR hybrid variety]) x 11 N treatments (kg N/ha) with timing spread between seeding, and up to 12 weeks after sowing (see Table 2)
Replicates Three
Sowing date 29 April
Seeding rate Target density 30 plants/m2 - Sturt TT 2.4kg/ha, Pioneer 43Y23 RR 1.5kg/ha
Table 2 Treatment details
Treatment Name Seeding 8WAS 12WAS Total N
1 Nil 0 0 0 0
2 10N seeding 10 0 0 10
3 30N in eight weeks 10 20 0 30
4 50N in eight weeks 10 40 0 50
5 70N in eight weeks 10 60 0 70
6 10N seeding and 20N 12WAS 10 0 20 30
7 10N seeding and 40N 12WAS 10 0 40 50
8 10N seeding and 60N 12WAS 10 0 60 70
9 30N in eight weeks and 10N 12WAS 10 20 10 40
10 30N in eight weeks and 12N 12WAS 10 20 20 50
11 30N in eight weeks and 40N 12WAS 10 20 40 70

Assumptions used in gross margins

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

Additional costs such as seeding, harvest, insecticides assumed to be $205/ha.

Nitrogen costs: $1.33/kg or $1.5/L, application costs $8/ha.

RR costs: seed $76/ha, herbicides $56/ha, grain worth $513t (five year decile price).

TT costs: seed $5/ha, herbicides $64/ha, grain worth $535/t.

Results

Pioneer 43Y23 (RR) and Sturt TT performed similarly in terms of grain yield, oil yield and gross margin and responded in a similar fashion to applied N. Sturt (TT) produced higher oil % than Pioneer 43Y23 (RR).

Table 3 Grain yield, oil %, oil yield and gross margin (mean of varieties) response of canola to nitrogen application at Chapman in 2014
- Pioneer 43Y23RR Sturt TT P LSD
Grain yield 1035 750 0.137 172
Oil % 42.1 44.2 0.01 0.6
Oil yield (kg/ha) 435 331 0.18 75
Gross margin ($/ha) 54 88 0.419 165

Response to N

Grain yield responded to applied nitrogen (P = <.001) up to ~70kg N/ha (~36kg soil plus applied N/ha), attaining yields of 0.9t/ha, oil yield 0.4t/ha and gross margins $71/ha.

Gross margins responded to nitrogen application at 40-70kg N/ha.

Timing of nitrogen

Overall when nitrogen was applied did not alter the response to nitrogen of both varieties. There was a trend (P = 0.006) at the highest rate of applied nitrogen of 70kg/ha (10 at seeding and 60 at a later date) for applications of the top-up of 60kg/ha that occurred at 12 weeks to be slightly lower yielding than the same top-up of nitrogen applied at eight weeks. If the same total nitrogen was split so as to apply 30 within eight weeks and the remaining 40 at 12 weeks there were no significant differences.

Canola grain yield responded to 70 kg of N
Figure 1 Grain yield response (mean of varieties) of canola to nitrogen application and timing at Chapman in 2014

Conclusion

In this trial both varieties performed similarly. Grain yield responded to applied nitrogen up to 70kg/ha. Oil did not decrease as nitrogen rate increased, unlike what we have observed at other trials – probably a reflection of the continued grain yield response to N. Positive gross margin returns were seen at 40-70kg/ha of applied nitrogen.

Overall when nitrogen was applied did not alter the response to nitrogen. There was a trend at the highest rate of applied nitrogen of 70kg/ha (10 at seeding and 60 at a later date) for applications of the top-up of 60kg/ha that occurred at 12 weeks to be slightly lower yielding than the same top-up of nitrogen applied at eight weeks. If the same total nitrogen was split so as to apply 30 within eight weeks and the remaining 40 at 12 weeks there were no significant differences.

Acknowledgements

This trial (14CH26) is one of a series conducted throughout WA as part of the GRDC/DPIRD co-funded project Tactical Break Crop Agronomy in Western Australia. Thanks to the local RSU for trial management. Stephanie Boyce and Jo Walker provided technical assistance to ensure all treatments and measurements occurred in a timely and accurate fashion.

Contact information

Martin Harries
+61 (0)8 9956 8553
Mark Seymour
+61 (0)8 9083 1143
Sally Sprigg
+61 (0)8 9081 3153