Timing of nitrogen in low rainfall canola, Wongan Hills 2014 trial report

Page last updated: Wednesday, 27 March 2019 - 10:41am

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

  • Grain yield responded to applied nitrogen up to 30kg N/ha.
  • Highest oil %, oil yield and gross margins were obtained with no applied nitrogen.
  • When nitrogen was applied, did not alter the yield, oil or $/ha response to nitrogen of both varieties.
  • Thus 30, 50 or 70kg N/ha applied either in splits at seeding and eight weeks or seeding and 12 weeks provided similar responses.

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 Wongan Hills Research Station
Growing season rainfall (GSR, April to Oct) 242mm, GSR + stored water (estimate) = 323mm. Long term average (LTA, 1974on) 270mm and 309mm
Soil type Yellow deep sand (1.2% organic carbon), estimated to be 123kg N/ha available in paddock from soil and plant residues
Paddock rotation 2013 - wheat, 2012 - pasture, 2011 - pasture, 2010 - barley
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 13 May
Seeding rate 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 2 Treatment details table
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 20N 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 (5 year decile price).

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

Results

Pioneer 43Y23 (RR) had similar grain yield, oil, oil yield and gross margins to Sturt (TT).

Table 3 Grain yield, oil %, oil yield and gross margin of two canola varieties at Wongan Hills in 2014
- Pioneer 43Y23RR Sturt TT P LSD
Grain yield (kg/ha) 756 697 0.202 68
Oil % 42.5 42.9 0.572 0.7
Oil yield (kg/ha) 321 299 0.312 32
Gross margin ($/ha) 40 61 0.385 37

Response to N

Grain yield responded to applied nitrogen up to ~30 kgN/ha, attaining yields of 0.73t/ha. Whilst highest oil %, oil yield and gross margins were obtained with no applied nitrogen. Both varieties responded similarly to applied nitrogen with no variety x N rate interaction for grain yield.

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

The highest gross margins (GM) were seen at the nil, with a mean GM of $97/ha, and by 30N in eight weeks. Gross margins decreased as nitrogen rates increased above 30kg N/ha. As for oil and yield, the gross margins of both varieties responded similarly to nitrogen rate (no variety x N interaction).

Table 4 Grain yield, oil %, and gross margin (mean of varieties) response of canola to nitrogen application at Wongan Hills in 2014
N GY Oil GM
0 674 43.8 97
10 647 43.3 60
30 732 43.0 72
40 749 42.6 60
50 742 42.5 46
70 744 42.1 18
N P 0.006 <0.001 <0.001
LSD 57 0.6 32
N x variety P 0.574 0.219 0.663

Timing of nitrogen

When nitrogen was applied, it did not alter the yield, oil or $/ha response to nitrogen of both varieties. Thus 30, 50 or 70kg N/ha applied either in splits at seeding and eight weeks or seeding and 12 weeks provided similar responses.

Conclusion

In this trial both varieties performed similarly. Grain yield responded to applied nitrogen up to 30kg N/ha. Whilst highest oil %, oil yield and gross margins were obtained with no applied nitrogen. As the rate of applied nitrogen increased the % oil in the seed of both canola varieties decreased at a rate of 0.02% oil per kg applied N/ha. Gross margins decreased as nitrogen rates increased above 30kg N/ha.

Overall when nitrogen was applied, did not alter the yield, oil or $/ha response to nitrogen of both varieties. Thus 30, 50 or 70kg N/ha applied either in splits at seeding and eight weeks or seeding and 12 weeks provided similar responses.

Acknowledgements

This trial (14WH11) 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 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