Pre Crop

  • Use tools and paddock knowledge to estimate the level of additional nitrogen required to meet potential crop yield.
  • Assess the costs, benefits and risk of various nitrogen application rates against the probability of potential yield being achieved.

In crop

  • Compare the costs, benefits, and risk of each fertiliser option against doing nothing
  • Consider nitrogen use efficiency and the potential risk of leaching and costs of further fertiliser application.
  • Undertake a “what if” scenario analysis to see what impact changing assumptions on key variables (e.g.  grain price and seasonal conditions), have on the costs.

Post Crop

  • Other than after a drought there is unlikely to be any residual nitrogen from the fertiliser in the soil.

Further details:

Pre Crop

  • Use tools and paddock knowledge to estimate the level of additional nitrogen required to meet potential crop yield.
    • Use tools (such as the Select Your Nitrogen calculator) that combine 0–10 cm soil organic carbon value, soil type, and legume history to assist in calculating nitrogen fertiliser requirement.
    • Consider possibility of leaching over summer.
  • Assess the costs, benefits and risk of various nitrogen application rates against the probability of potential yield being achieved.
    • Use tools to compare costs, yield response and protein under various seasonal scenarios. Assess each result with probability of the scenario occurring.
    • Consider staged application to be flexible with the season.
    • Assess the risk of fertiliser seed toxicity and consider taking mitigating action.
    • Consider other yield limiting constraints or deficiencies that will limit the responsiveness of nitrogen application.
    • Estimate the loss in potential yield (opportunity cost), and therefore revenue and profit impact, associated with low or no nitrogen fertiliser application

 

In Crop

  • Compare the costs, benefits, and risk of each fertiliser option against doing nothing
    • Tools such as SYN and Yield Prophet can help you adjust nitrogen decisions for yield potential and leaching changes during the season.
    • What are the likely outcomes of each fertiliser option? When the yield response of fertiliser is not known with certainty, due to factors such as seasonal influences, consider the most likely (expected), as well as the worst and best results from each option.
    • Consider choosing a fertiliser option where the expected return is sufficient to offset the risk of lower than expected response rates.
    • Weigh up the costs and benefits of various nitrogen application methods, ie top-dress, spraying etc.
    • Consider the impact on grain protein percentage as well as yield when calculating price received as there may be an inverse relationship with yield and protein.
    • Consider the growth stage of the plant. Is it too advanced to respond and therefore not economic?
    • Is more fertiliser economic for the additional (marginal) yield response that is most likely?
    • Are there any other constraints to estimated yield potential? If so, would addressing these be more economic?
    • Will the rain following application be enough to achieve yield potential? Consider various finishing scenarios in your analysis.
  • Consider nitrogen use efficiency and the potential risk of leaching and costs of further fertiliser application.
  • Undertake a “what if” scenario analysis to see what impact changing assumptions on key variables (e.g.  grain price and seasonal conditions), have on the costs.
    • Some variables can influence decision outcomes but are not directly controllable, including fluctuations in wheat price, the value of the Australian dollar and seasonal influences. But they need to be considered, even if we can’t include them directly. A “what if” analysis may help you in your decision making.

Post Crop

  • Other than after a drought there is unlikely to be any residual nitrogen from the fertiliser in the soil.
    • A general rule of thumb is that there is no residual nitrogen after 250mm growing season rainfall (less if carryover moisture from summer rains).