NEW research has found that taking a tactical approach to nitrogen (N) applications based on environmental conditions can provide opportunities that might otherwise be overlooked.
The Tactical Wheat Agronomy for Western Australia research project, a joint Department of Primary Industries and Regional Development (DPIRD) and Grains Research and Development Corporation (GRDC) investment, has challenged conventional thinking about when to apply nitrogen.
The research project involved trials across the Wheatbelt and revealed a key influencer of wheat yield, quality and protein level is environment.
DPIRD research officer Dion Nicol said the tactical nitrogen agronomy research was conducted over three years and looked at differences in nitrogen timing for varieties.
"However it was quite clear early on in the project that the differences were mostly driven by environment, rather than differences between varieties," Dr Nicol said.
"The advantage of deferring nitrogen application is also that growers can identify those paddocks that are deficient, identify the amount of soil water available and how the season is tracking.
"That allows them to see what they're yield potential is based on, what they've got to date and when there's a gap, they can fertilise for that."
While the research is not suggesting starter nitrogen applications at seeding be abandoned, it has revealed that by delaying N applications, additional crop management opportunities can be considered.
The trial data also indicated that by taking more of a tactical approach to the timing of nitrogen fertiliser applications, WA's wheat growers might significantly improve grain quality without yield penalty.
"The impact of nitrogen timing would have an increase in protein while maintaining the equal best yield," Dr Nicol said.
"What that tended to mean is that you got a great nitrogen recovery, so in terms of putting the equivalent of nitrogen out, you got more back as protein per hectare."
The trials found deficiencies could be addressed until flag leaf emergence without yield loss, provided there was rainfall to incorporate the nitrogen and enough time left in the season.
Dr Nicol said dry conditions could limit some of the later applications but as yield potential increased in better conditions, the window tended to widen.
"What we can see is that the length of time you can defer is driven by the environmental conditions and your risk of dry spell and poor uptake, rather than the development stage of crops," he said.
"What this means is that in earlier sown crops you potentially have more time than those than are late sown."
As a result, growers can consider their in-season nitrogen timing more around their environment and likely conditions across a season, rather than a strict adherence to growth stage-based decision.
"If the season improves as it progresses and there is a gap in your nitrogen budget, it's not too late," Dr Nicol said.
"Optimising the rate is always a tricky question, it's a dynamic problem, but with the timing there is no yield penalty in coming back later, provided you can get that uptake of nitrogen."