SUM20.33: Apex Yield Series – Strategic Nitrogen Rates & Timing for Wheat on Heavy Loam Soil, Mingenew


This trial assesses a number of nitrogen application strategies with increasing rates to match site conditions and Scepter wheat yield potential at a loamy site south east of Mingenew. Nitrogen was applied at different rates and timings; either early (at 5 and 8 weeks after emergence) or late (at 8 and 12 weeks after emergence).

Trial Details

Location: Mingenew.

Trial Size: 1.61m x 10m, 13 treatments x 3 reps = 39 plots.

Soil Type: Loamy Sand.

Crop Sown: Scepter Wheat, sown 11/05/2020 at 100kg/ha.

Season Rainfall: 260 mm, Yandanooka BOM, 34 mm below long-term average.

Table 1: Pre-trial soil nutrient analysis.


Figure1: Harvest yield (bar) were generally higher in early application of N and grain protein (line) with no consistent trends between early and late. The fuel gauge treatments showed an increase in protein as rate of N applied increased.

Figure 2: Yield response to early and late N applications, a stronger yield response to increasing N rates for early than late application. Mitscherlich function fitted to both treatments

Figure 3: Individual gross margin returns show an economic advantage to applying N early or based on N-Calc recommendations.

Key Messages

  • Plant biomass responded strongly to increasing N. Growth differences became greater as the season progressed.
  • Grain yield averaged 3.1t/ha, with a 1.5t/ha variation across applied N rates.
  • The importance of avoiding ‘hidden hunger’ was evidenced in significantly higher yields and returns from early applications of nitrogen compared to late applications.
  • Applying N at 5 and 8 weeks after emergence indicatively returned an average $80/ha more profit than application at 8 and 12 weeks. Late applications require more N to catch yield from earlier applications, putting them at an input disadvantage.
  • Under 2020 growing season conditions the most profitable treatment was applying 85kg N/ha early with a return of $950/ha.

For further information about this trial please get in touch with local Area Manager Juliet McDonald,