With hybrid varieties of canola becoming dominant in the Northern Agricultural Region (NAR), breeders of these varieties have been suggesting that early, high rates of nitrogen (N) are required to maximise their yield potential. The NAR can have highly variable seasons so it can be difficult for growers to gauge potential yield early in the season. What we need are risk management strategies to meet yield potential in good seasons and avoid over fertilising in poorer seasons.
CSBP conducted trials in the NAR in 2019 and 2021. The trials looked at the effects of N timing on the growth and yield of hybrid canola, with a particular focus on comparing early high N rates to the more conventional method of splitting the N fertiliser between an early and later application.
The two seasons were very different. In 2019 the break of the season didn’t occur until late May, which was then followed by a deluge of rain for six weeks, and then very dry conditions from early July to the end of September. In 2021 the break for canola occurred with the passing of Cyclone Seroja in early April, and rainfall was average to above-average to the middle of August followed by a dry September.
The trials suggest that with these hybrid varieties, growers can be more flexible with their N applications. Yields were similar whether all the N was applied in the early growth stages (before the 8-leaf stage), or with some applied early and some later (at the bud visible stage). Compare the yields in row 2 (all early N) and row 3 (split N) in Tables 1-3.
2019, Casuarina. Sown with 43Y27.
2021, Northampton. Sown with Raptor.
2021, Tenindewa. Sown with HY410XX.
The season matters
Applying all the N at the bud visible stage delayed flowering at all three sites, compared to plots that had at least 50% of the N applied early. This led to significant differences in yields depending on the season.
In 2021, the plots at Northampton and Tenindewa were showing visual symptoms of N deficiency at the time of application (bud visible stage), but there was no yield penalty. Yield loss did not occur as these plots had enough time to respond as the N was applied in the middle of the growing season (late June) when there was good rainfall.
A delay in flowering is less than ideal in a year when canola is germinating in early June and seasonal conditions are dry (Table 1, Casuarina, in the south west of the Mullewa Shire 2019). The delay in flowering meant a significant yield loss in a year when yields were very poor, as the canola did not have enough time to respond to the nitrogen fertiliser.
When topping up canola with N it is important to not only consider the crop growth stage, but also the time of the growing season. This will give the crop every chance to have the time and moisture to respond.
Image: Canola flowering delay at Tenindewa.
Learn more about our Flexi-N range here: csbp-fertilisers.com.au/products/cropping/liquids