SUM19-05: Factorial Nitrogen x Phosphorus Rate Trial in Scepter Wheat, Tammin


To evaluate the response of wheat to nitrogen (N) and phosphorus (P) fertilizer application at a sandy clay site east of Tammin.

Trial Details

Location: Tammin, Bungulla Farms (Brad Jones).

Trial Size: 64 plots.

Soil Type: Sandy clay.

Crop Sown: Scepter Wheat, 88kg/ha, 16/05/2019.

Table 1: Pre-trial soil nutrient analysis.


Figure 1: Harvest yield (bars) and grain protein (lines) increase with increasing N and P applied. 75kg N/ha and 18kg P/ha was the highest yielding treatment and 75kg N and nil P had highest protein.


Figure 2: Return additional to average gross margin returns from control (Nil N). Data shows the combination of P and N contributing to profits with P alone having a small impact under the seasonal conditions but an important requirement for maximising return from N. Optimal P rate was 6 kg/ha and optimal N 50 kg/ha.

Key Notes

  • Growth, yield and grain quality performance was relatively poor due to seasonal and site conditions.
  • Increasing both N and P rate improved Scepter wheat performance but with an average site yield of 1.0t/ha only N application up to 50 kg/ha was cashflow positive.
  • Increasing rates of N applied increased gross margin returns additional to nil control treatments, whereas increasing rates of P alone did not, however without establishment P, profits from N were more than halved.

Contact your local Area Manager Tracey Hobbs for more details on this trial, 0429 470 007.