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

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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.


In a dry year, there was no economic response to applied N.


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 Liebe Group main trial site: Fitzsimons Farm – 17km east of Buntine along Dinnie Rd, East Buntine
Growing season rainfall (GSR, April to Oct) 136mm, GSR + stored water (estimate) = 186mm. Long term average (LTA, 1974on) 242mm and 283mm.
Soil type Sand over gravel (0.88% organic carbon), estimated to be 54kg N/ha available in paddock from soil and plant residues
Paddock rotation 2013 - wheat, 2012 - canola, 2011 - wheat, 2010 - lupin
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 1 May
Seeding rate Target density 30 plants/m2 - Sturt TT 2.4kg/ha, Pioneer 43Y23 RR 1.5kg/ha
Basal fertiliser 80kg/ha of MacroPro Plus (10%N, 14%P, 8.4%K, 8%S, Cu 0.1, Zn 0.2, Mn 0.01) at seeding – error resulting in all plots receiving 8kg N/ha
Table 2 Treatment details
Treatment Name Seeding  8WAS 12WAS Total N
1 8N seeding 8* 0 0 0
2 18N seeding 18 0 0 10
3 30N in eight weeks 18 12 0 30
4 50N in eight weeks 18 32 0 50
5 70N in eight weeks 18 52 0 70
6 18N seeding and 12N 12WAS 18 0 12 30
7 18N seeding and 32N 12WAS 18 0 32 50
8 18N seeding and 52N 12WAS 18 0 52 70
9 30N in eight weeks and 10N 12WAS 18 12 10 40
10 30N in eight weeks and 20N in 12WAS 18 12 20 50
11 30N in eight weeks and 40N 12WAS 18 12 40 70

*Due to MacroPro Plus being used at sowing instead of SuperPhos

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 $113/ha.

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

RR costs: seed $76/ha, herbicides $47/ha, grain worth $513t (five year decile price)

TT costs: seed $5/ha, herbicides $56/ha, grain worth $535/t


Below average rainfall in June, July and August resulted in low grain yields of around 0.5t/ha. Consequently the response to N was limited and gross margins were maximised at the lowest rate of applied N of 8kg N/ha.

Pioneer 43Y23 (RR) and Sturt (TT) performed similarly in terms of grain yield, oil %, oil yield and gross margins.

Grain yield (P = 0.88) and oil yield (P = 0.72) did not respond to applied nitrogen. The highest rates of N of 50 and 70 reduced oil %. Both varieties responded similarly to applied nitrogen with no variety x N rate interaction for grain yield, oil %, oil yield and gross margin. When nitrogen was applied did not alter the response to nitrogen of both varieties for GY (P = 0.42), oil % (P = 0.16), oil yield (P = 0.364) and gross margin (P= 0.38).


In a dry year, there was no economic response to applied N.


This trial (14WH10) 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