SUM19-11: Factorial Phosphorus x Potassium Rates in wheat, Mukinbudin


To evaluate the response of wheat to phosphorus (P) and potassium (K) fertilizer application at a sandy loam site south of Mukinbudin.

Trial Details

Location: Tim & Dudley Squire, Mukinbudin.

Trial Size: 12 trts x 4 reps = 48 plots.

Soil Type: Sandy loam.

Crop Sown: Scepter Wheat, 79kg/ha,  14/05/2019.

Table 1: Pre-trial soil test analysis.


Figure 1: Individual treatment yield (bars) and protein (lines) presented as the mean across 4 replicates. There is a significant increase in yield with applied P.
Figure 2: Individual treatment gross margins showing the variability in grain segregation as rate of K applied increases.

Key Notes

  • Mukinbudin experienced a decile 3 growing season rainfall in 2019 with significant dry periods during early April to mid-June, most of July and all September; this rainfall pattern severely impacted the yield potential in this trial.
  • Increasing rates of P and K did not affect emergence, with an average of 152 plants/m2
  • Plant vigour significantly increased as rates of P applied increased, although higher rates of K did not have the same effect.
  • Tissue tests indicated a significant increase in P and K uptake with higher rates of P applied, with K application not having the same effect.
  • Yield significantly increased as rate of P applied increased, although grading was limited by high screenings.
  • Under 2019 conditions the most profitable treatment was $360/ha when 18kg P/ha and 20kg K/ha was applied.

Contact local Area Manager, Kobus Marais, 0427 766 508 for more details on this trial.