Field Research & Agronomy

Potassium strategies and phosphorus rates in wheat

AIM:

To determine the optimal strategy and form for applying potassium fertiliser in the Borden area, whilst also investigating phosphorus rates.

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

KEY MESSAGES

• Greater than 1 t/ha yield response was measured to phosphorus at 20 kg/ha (P
• Yield and returns were optimised at 15-20 kg/ha of P and 10 kg/ha of K.
• Under high yielding scenarios, extra care should be taken to replace P and K exported with the grain to avoid nutrient mining and safeguard subsequent crops.
  

CONCLUSIONS

• Greater than 1 t/ha yield response was measured to phosphorus at 10 and 20 kg/ha compared to 0P.
• A similar NDVI response to K was measured between MOP topdressed immediately before sowing (IBS), MOP banded below the seed, and K supplied in a complete compound granule - Vigour® .
  At the high K rate, Vigour treatments looked to have a slight advantage over MOP topdressed or banded but this was not statistically significant.
• Despite early biomass indications, there was no significant yield response to K rate or placement. Vigour® and MOP topdressed IBS showed a similar response to K rate whereas MOP banded had faded at the 20K rate (Figure 4b). It is conceivable that 40 kg/ha of MOP banded (20K) could have caused chloride toxicity issues for the seedling, limiting germination and future yield potential
• Phosphorus at 15-20kg/ha supplemented with 10kg/ha of K would be a solid nutrition strategy to maximise returns under these conditions.

Potassium export should be noted particularly with high yielding crops; ~4kg of K is removed with each tonne of wheat harvested. With mid-range soil K levels (71ppm), maintenance K should be applied to avoid nutrient mining and to safeguard future crops.