Nitrogen management in Western Australia is extraordinarily difficult for one simple reason - it is near impossible to know what the yield potential of the crop will be for the current season.
Because of that nitrogen management becomes a guessing game, and while there are tools available to help manage the between season variability, picking a target yield and fertilising to that yield, regardless of the season is still effective.
CSBP senior agronomist James Easton said the need for nitrogen fertiliser depended on both the amount of nitrogen in the soil and the yield potential.
"We can test our soils and take into account paddock rotations to estimate nitrogen supply, but the tricky bit is estimating yield potential," Mr Easton said.
"Nitrogen management is difficult because we can't predict the season we are going to get."
However, there are tactics and tools that growers can implement in order to make better nitrogen decisions.
Growers need to be realistic with their yield targets and also consider soil nitrogen reserves, as with continuous cropping they are a lot lower than what they used to be, especially without legumes in the rotation
On top of that, it is critical that growers understand the soil constraints - either address them or respect them - and also ensure that other nutrients are not limited by testing the soils and the crops.
"If overcoming a soil constraint increases the potential of a wheat crop by one tonne per hectare, an extra 40 to 50 kilograms of nitrogen per hectare is required if that potential is going to be realised," Mr Easton said.
"This is also the amount of additional nitrogen that is required to realise another 0.5 t/ha of canola yield potential - and that may be possible due to earlier crop establishment, better varieties, agronomic practices etc."
Continuous cropping has depleted soil nitrogen reserves and without productive legumes in the rotation, there is an increased reliance on nitrogen fertiliser.
Mr Easton said low grain proteins in past crops were a good indicator that nitrogen supply had limited yields.
"Experience tells us if and where that is likely to be the case, we should be thinking about whether we are applying enough nitrogen or re-visiting our paddock rotations," he said.
"Profitable responses to nitrogen are dependent upon other nutrients not limiting - soil and plant testing are important tools for monitoring and managing the supply of the other essential nutrients."
To manage nitrogen more precisely, data must be captured about the soil nitrogen supply, the crop nitrogen status and the likely yield potential, given the soil water status and future weather.
Problems, such as the disease status or soil constraints need to be captured and considered as well.
This information will need to be quickly communicated to the grower and agronomist through a mobile device, plus the information needs to be integrated to create a nitrogen recommendation that also communicates how risky that recommendation is.
Luckily for growers, all of that technology is available today and in the near future, it will become cheaper, better integrated and more user-friendly.
