SUM20.14: Potassium and Phosphorus Rate Interactions for Noodle Wheat production, Nungarin


Assessing standard crop fertilizer practice against new strategies. This trial investigates the interactions between increasing phosphorus (P) and potassium (K) interactions on a noodle wheat at a sandy clay loam site southwest of Nungarin. With hope to increase knowledge of P and K importance in wheat yield and grain quality.

Trial Details

Location: Nungarin.

Trial Size: 2.2m x 10m, 12 treatments x 4 reps = 48 plots.

Soil Type: Sandy Clay Loam.

Crop Sown: Ninja Wheat, sown 18/05/2020 at 90kg/ha.

Season Rainfall: 220 mm, Trayning West DPIRD, 9 mm above long-term average.

Table 1: Pre-trial soil nutrient analysis


Figure 1: Harvest yield (bars) and grain protein (lines) across four replicates. There is a significant increase in yield with applied K.

Figure 2: a) Responses to increasing P rate applications, with increasing rates of K applied. b) Increasing yield response to increasing K rates, with little differentiation between P rates. Mitscherlichfunction fitted to all lines.

Figure 4: Returns additional to average gross margin returns from control (P0 K0). a)The addition of P increased profits by approximately 13% at 12kg P/ha. b) The addition of K also increased profits, to a high of 36% at 40kg K/ha.

Key Messages

  • Plant vigour significantly increased as rates of P and K applied increased.
  • Yield increased with increasing rates of both P and K, ranging between 1.34t/ha and 2.08t/ha.
  • The most profitable treatment was 40kg K/ha and 12kg P/ha, returning $520/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 Kobus Marais