With grain yield of less than 400kg/ha, there was no grain yield response to applied N and no economic response to applied N.
At ‘low rainfall’ N rates of 30kg/ha top-up N at 12 weeks gave a similar response to top-up N within eight weeks.
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).
|Property||Merredin Research Station|
|Growing season rainfall (GSR, April to October)||193mm, GSR + stored water (estimate) = 255mm. Long term average (LTA, 1974on) 203mm and 240mm. Lower than LTA June and July, but above average September|
|Soil type||Brown sandy loam (1.08% organic carbon), estimated to be 124kg N/ha available in paddock from soil and plant residues|
|Paddock rotation||2013 - wheat, 2012 - wheat, 2011 - wheat, 2010 - 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)|
|Sowing date||13 May|
|Seeding rate||Target density 30 plants/m2 - Sturt TT 2.4kg/ha, Pioneer 43Y23 RR 1.5kg/ha,100kg/ha of Doublephos at seeding, 400kg/ha of gypsum (17% Ca, 14% S) top-dressed over whole site before sowing (kg/ha) and 120kg/ha of Muriate of Potash top-dressed over whole site 27 June|
|Basal fertiliser||100kg/ha of Doublephos at seeding, 400kg/ha of gypsum (17% Ca, 14% S) top-dressed over whole site before sowing (kg/ha) and 120kg/ha of Muriate of Potash top-dressed over whole site 27 June|
|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 amd 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 $126/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
Grain yield and gross margin results for this trial were extremely poor. Treatments had no significant effect on grain yield. Applying N reduced the concentration of oil of both varieties by an average of 0.08 units of oil per kg of applied N. The loss of oil with applied N combined with the cost of N resulted in a negative gross margin response to applied N.
At rates of N most commonly used in low rainfall areas of less than 30kg N/ha, it did not appear to matter when N was applied. Applying 30N within eight weeks or applying 10 at seeding and a top up at 12 weeks produced the same level of oil. At higher rates of total applied N it appeared timing of N had did alter the oil in the seed of canola. At a total rate of applied N of 50 or 70 applying 10 at seeding and then the top up at 12 weeks gave similar results to applying the top up N within eight weeks, however if the N was applied in more of a ‘split application’ with 30N within eight weeks and the top up at 12 weeks oil levels dropped. However applying 30N within eight weeks and then applying more at 12 weeks is highly unlikely to be undertaken by growers in low rainfall areas.
Sturt produced higher oil then Pioneer 43Y23 RR, but there were no differences between varieties for grain yield or gross margins. In addition there were no interactions between variety and N treatments.
|N Treatment||Pioneer 43Y23 RR||Sturt||Pioneer 43Y23 RR||Sturt||Mean||Pioneer 43Y23 RR||Sturt||Mean|
|30N in eight weeks||212||301||40.6||40.2||40.4||-225||-155||-190|
|50N in eight weeks||221||249||38.1||39.2||38.7||-254||-212||-233|
|70N in eight weeks||212||259||38.3||39.5||38.9||-287||-235||-261|
|30N in eight weeks and 10N 12WAS||197||245||38.7||39.7||39.2||-250||-198||-224|
|30N in eight weeks and 20N 12WAS||240||207||37.1||37.9||37.5||-247||-234||-240|
|30N in eight weeks and 40N 12WAS||245||197||36.0||37.7||36.8||-277||-268||-273|
|10N seeding and 20N 12WAS||250||188||40.7||40.1||40.4||-206||-212||-209|
|10N seeding and 40N 12WAS||206||250||38.1||39.8||38.9||-261||-210||-235|
|10N seeding and 60N 12WAS||202||216||37.8||38.9||38.3||-293||-257||-275|
With reasonably high background N levels in the paddock and low yield potential, the best option was to not apply N.
This trial (14MR18) 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.