Field Research & Agronomy

TIMING AND RATES OF NITROGEN ON CANOLA

BACKGROUND

Nitrogen influences aspects of both vegetative growth and oil production in canola. Growers are continually seeking information about optimal strategies in terms of rate and timing of applications to maximise grain production while maintaining the ability to get that grain off at harvest.

Elsewhere in the state, anecdotal observations have been made of a shortened flowering window following N application to canola crops where flowering has started.
Yet, there is little well-recorded evidence of timings, relative crop stages and seasonal conditions to provide hard data to this effect.
With this in mind, we initiated a trial incorporating N application at different rates and at different times in a canola crop to record and observe the impacts on the length of flowering occurrence in the season and, ultimately, yield and oil production.

For further information on this trial contact your local Area Manager or our field research team on research@summitfertz.com.au

1. Early biomass responses followed through to yield where there was a significant response to applied nitrogen.
   
   
2. The N Gauge treatment (126N upfront), which aims to provide an unlimited source of nitrogen throughout the growing season, had the highest yield of 1.84 t/ha.
   
   
3. 72 kg/ha of nitrogen maximised returns under these conditions.
   
   
4. There was no significant difference in yield between timings of nitrogen application, even when nitrogen was applied at full flowering.
   
   
5. Timing and rate of nitrogen did not affect grain quality under these conditions. All treatments were close to 50% oil and received the subsequent oil bonuses.
   
   
6. The N-calculator recommended top-up rate of 17kg N/ha generated yield and returns very near the top of the response curve.
   

CONCLUSION

There was a significant yield response to nitrogen rate but not to timing of application under these conditions. Earlier nitrogen applications were observed to pod sooner and subsequently lose flowers compared to later applications, which flowered for longer.
These flowering observations did not result in any significant yield differences come harvest.

Harvest yield and gross margin were optimised at ~70kg/ha of nitrogen.
The insignificant difference in yield and quality between top up timings could provide growers with the flexibility to delay nitrogen decisions.
The highest yielding treatment was the N-Gauge where all N was applied upfront. Having enough nitrogen upfront is vital to avoid serious yield penalties and to utilise later N top-ups efficiently, all top-up treatments in this trial received 33 kg/ha of N at sowing.

Interestingly, grain quality was not affected by nitrogen rate or timing under these conditions. All treatments had close to 50% oil and received the subsequent oil bonuses.
100 kg/ha of Vigour® and 50 kg/ha of urea at sowing (33N) with the addition of 140 L/ha of MaxamFlo (40N 11S) during the season seems to be a solid nitrogen strategy for canola under these conditions.