Sum15-17 Tactical N with Fuel Gauges


Demonstrate and evaluate nitrogen-rich strips (N Gauges) and Normalised Difference Vegetation Index (NDVI) measurement as decision support tools to guide economic application of nitrogen during the growing season.

For further details contact yor local Area Manager or the Summit Research Team


  • Summit’s In-Season Nitrogen Calculator aims to calculate a precise N rate to maximize yield potential of a paddock where N may be limiting, using NDVI as on-the-spot growth measurement.

  • This trial demonstrates using dynamic and real-time comparisons between growth of wheat with and without N limitations to determine optimal N application for yield and returns.

  • The Nitrogen Calculator shows real promise on light country in the northern wheat belt.
    The Calculator optimised yield and gross margin at the 9WAS application and gave a reasonable estimation of optimal N rate at 7WAS.

  • Summit’s In-Season N Calculator adds another tool to predict yield potential during a broad window of the growing season so growers can have increased confidence in their N application decisions,
    decreasing risks of over-application and inefficient fertilizer usage.
Fig 1: Yield and Protein


  • N Calculator recommendation was accurate for 9WAS application with additional nitrogen not increasing yield. The recommendation was slightly below optimum for 7WAS application.

  • Achieving close to the target 10.5% protein indicates that recommended N rates were utilised to optimise growth and yield and application of N was not deficient or excessive.

  • This provides confidence to incorporate the use of N-gauges and the N Calculator to assist in making N application decisions to wheat crops during the season based on the growth status of the crop.

  • Summit will continue further testing of the N Calculator under different seasonal conditions in the northern wheat belt and the effect of timing of NDVI assessment and N-calculator recommendations on yield response to in-season N applications.