Summary
With grain yield of less than 1t/ha, there was only a small grain yield response to applied N and no economic response to applied N. Top-up N at 12 weeks gave a similar response to top-up N at eight 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
| Property | Tim, Dave and Fiona Osborne’s, Eldred Road, Salmon Gums |
|---|---|
| Agzone 5 growing season rainfall (GSR, April to October) | 175mm, GSR + stored water (estimate) = 198mm |
| Soil type | Sandy loam (0.7% organic carbon), estimated to be 58kg N/ha available in paddock from soil and plant residues |
| Paddock rotation | 2013 - barley. 2012 - wheat, 2011 - wheat, 2010 - field pea |
| 22 treatments | Two cultivars (Sturt TT [TT open-pollinated variety] and Pioneer 43Y23RR [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 | 17 April |
| Seeding rate | Target density 30 plants/m2 - Sturt TT 2.4kg/ha, Pioneer 43Y23RR 1.5kg/ha |
| Basal fertiliser | 400kg/ha of gypsum (17% Ca, 14% S) top-dressed over whole site before sowing (kg/ha),100kg/ha of Impact treated Superphos at seeding, 120kg/ha of Muriate of Potash top-dressed over whole site four weeks after seeding |
| Treatment | Name | Seeding | 8WAS | 12WAS | Total N |
|---|---|---|---|---|---|
| 1 | Nil | 0 | 0 | 0 | 0 |
| 2 | 10N seeding | 10 | 0 | 10 | 0 |
| 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 $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 (5 Year decile price)
TT costs: seed $5/ha, Herbicides $56/ha, Grain worth $535/t
Results
No difference between varieties therefore we are presenting the mean results only.
Conclusion
In a relatively dry growing season at Salmon Gums grain yield responded to around 30kg N/ha. The gain in yield was relatively small at around 5kg per unit of N applied and oil decreased with each kg of N. Therefore it was uneconomic to apply N to canola. When N was applied had no effect on the yield or oil response. This experiment is an example where by delaying N top-up until later in the year may have allowed growers to decide not to apply N.
Acknowledgements
This trial (14ED15) 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 Osborne family for hosting the trial and to the Esperance RSU for trial management. Pam Burgess (DPIRD Esperance) provided technical assistance to ensure all treatments and measurements occurred in a timely and accurate fashion.