SUM20.28: Nitrogen x Phosphorus Rates to Support Scepter Wheat Production, Tammin


Assessing standard crop fertiliser practice against new strategies. This trial assesses the response of wheat under a factorial nitrogen (N) and phosphorus (P) fertilizer application trial design in the Tammin area to increase recognition of the value of optimal N and P to wheat yield, grain quality and profitable returns.

Trial Details

Location: Tammin

Trial Size: 2.2m x 10m, 16 treatments x 4 reps = 64 plots.

Soil Type: Loamy sand.

Crop Sown: Scepter Wheat, sown 06/05/2020 at 80kg/ha.

Season Rainfall: 161 mm, BOM Bungulla, 76 mm below long-term average

Table 1: Pre trial soil nutrient analysis.


Figure 1: Harvest yield (bars) and grain protein (lines) across four replicates. Yield increased with applied N and P.

Figure 2: All yield response curves to N and P rate applications. There was a strong responseto both N and P and the relationship between responsiveness and applying sufficient rates of both nutrients is clear. Mitscherlich function is fitted to each dataset.

Figure 3. Grouped mean gross margins for applied P and N. Optimum returns come from 75Kg N/ha and 12kg P/ha.

Key Messages

  • Plant growth significantly increased with both applied N and P.
  • Yield increased with increasing rates of both N and P, ranging between 1.28t/ha and 2.45t/ha.
  • The most profitable treatment was 12kg P/ha and 75kg N/ha, returning $625/ha.
  • The trial data indicates there are significant increased profits to be made by small investment in establishing a strong foundation crop P status at sowing.

For further information about this trial please get in touch with local Area Manager Tracey Hobbs,