Timing of nitrogen in low rainfall canola, Cunderdin 2014 trial report

Page last updated: Wednesday, 27 March 2019 - 10:40am

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 Roundup ready (RR) hybrids respond to nitrogen has not been widely tested, particularly in low and medium rainfall areas.

Summary (key messages)

  • Pioneer 43Y23 (RR) perform better in terms of higher grain yield, oil yield and gross margins than Sturt TT, with both varieties producing similar oil percentage.
  • Grain yield responded to applied nitrogen up to 30kg N/ha.
  • Maximum oil percentage was produced with no applied nitrogen.
  • Gross margins also responded to nitrogen application up to approximately 30kg N/ha after which further increases in nitrogen led to no further financial gain.
  • Overall when nitrogen was applied it did not alter the response to nitrogen of both varieties for grain yield, oil, oil yield and gross margin.

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

  • Property: WANTFA site at Cunderdin
  • Growing season rainfall (GSR) (April to October): 266mm, GSR + stored water (estimate): 323mm, long term average (LTA) (from 1974 onwards): 206 and 246mm
  • Soil type: yellow-brown deep sandy duplex (1.49% organic carbon), estimated to be 46kg N/ha available in paddock from soil and plant residues
  • Paddock rotation: wheat 2013, canola 2012, wheat 2011, wheat 2010
  • 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 1)
  • Three replicates
  • Sowing date: 29 April
  • Seeding rate: target density 30 plants/m2 - Sturt TT 2.4kg/ha, Pioneer 43Y23 RR 1.5kg/ha
  • Basal fertiliser: 100kg/ha SuperPhos at seeding, 400kg/ha of gypsum and 120kg/ha of Muriate of Potash applied by hand over whole site on 10 June.
Table 1 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 8 weeks 10 20 0 30
4 50N in 8 weeks 10 40 0 50
5 70N in 8 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 8 weeks and 10N 12WAS 10 20 10 40
10 30N in 8 weeks and 20N 12WAS  10 20 20 50
11 30N in 8 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) had higher grain yield, oil yield and gross margins than Sturt TT, with both varieties producing similar oil percentage.

Table 2 Grain yield, oil %, oil yield and gross margin (mean of varieties) response of canola to nitrogen application at Cunderdin in 2014
  Pioneer 43Y23RR Sturt TT LSD
Grain yield (kg/ha) 1328 1049 79
Oil % 43.3 43.3 2.0
Oil yield (kg/ha) 575 454 52
Gross margin ($/ha) 672 537 53

Response to N

Grain yield responded to applied nitrogen up to approximately 30kg N/ha (approximately 85kg soil plus applied N/ha), attaining yields of 1.2t/ha, oil yield 0.5t/ha and gross margins $627/ha. Both varieties responded similarly to applied nitrogen with no variety x N rate interaction for grain yield.

Maximum oil percentage was produced with no applied nitrogen (mean oil percentage at 0N = 44.1%). As the rate of applied nitrogen increased the oil percentage in the seed of both canola varieties decreased at a rate of 0.02% oil per kilogram of applied N/ha. Both varieties responded at a similar rate (no variety x N interaction). The relatively slow decrease in oil percentage as nitrogen increased resulted in oil yield mirroring grain yield.

Gross margins also responded to nitrogen application up to approximately 30kg N/ha after which further increases in nitrogen led to no further financial gain. As for oil and yield, the gross margins of both varieties responded similarly to nitrogen rate (no variety x N interaction).

Timing of nitrogen

Overall when nitrogen was applied did not alter the response to nitrogen of both varieties (P = 0.05, for grain yield, oil, oil yield and gross margin). There was a trend (P<0.1) at the highest rate of applied nitrogen of 70kg/ha (10 and 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 differences.

Conclusion

The Cunderdin trial saw Pioneer 43Y23 (RR) perform better in terms of higher grain yield, oil yield and gross margins than Sturt TT, with both varieties producing similar oil percentage.

Grain yield responded to applied nitrogen up to 30kg N/ha.

As the rate of applied nitrogen increased the oil percentage in the seed of both canola varieties decreased at a rate of 0.02% oil per kilogram of applied N/ha.

Gross margins also responded to nitrogen application up to approximately 30kg N/ha after which further increases in nitrogen led to no further financial gain.

Overall when nitrogen was applied it did not alter the response to nitrogen of both varieties for grain yield, oil, oil yield and gross margin.

Acknowledgements

This trial (14NO17) is one of a series conducted throughout Western Australia as part of theGRDC/DPIRD co-funded project Tactical Break Crop Agronomy in Western Australia. Thanks to the Merredin RSU for trial management. Laurie Maiolo provided technical assistance to ensure all treatments and measurements occurred in a timely and accurate fashion.

Contact information

Mark Seymour
+61 (0)8 9083 1143
Sally Sprigg
+61 (0)8 9081 3153