Sum15-08 Nitrogen, Phosphorus and Potassium in Wheat, Merredin


Expanding the series of eastern wheat belt trials assessing how wheat responds to N and P fertilizer applications under different conditions by the addition of K.

For further details contact your local Area Manager or the Summit Research Team

Table 1: Soil Analysis
Fig 1: Grain Yield and Protein
Fig 2: Responses to P & N +/- K


  • Differences in yield between N and P treatments were significant and consistent with Summit trials over many years in the area and K application should be a consideration depending on results of soil testing.
  • Application of K at seeding improved yields at almost all P and N rates and markedly enhanced the response to increasing P rate.
  • Returns from lower N rates were improved by K application.
  • Yield and gross margins are optimised at recommended P 8-10 kg/ha and N 30-60 kg/ha, and growers should consider K applications where soil Colwell K is below 50 mg/kg in topsoil and decreases deeper in the profile.