Key Points
- In over twenty years of research in New Zealand, yield responses of maize grain to P or K fertilisers have been very uncommon
- In the US, yield responses to starter fertiliser are common, but often the starter fertiliser contains N and often the increase in yield is uneconomic
- This series of trials indicated that yield and economic responses of maize to P fertiliser should not be expected unless Olsen P is less than 10
- Growers may spend more than $130/ha on P fertilisers that give no yield response
- Further research is needed to define agronomic responses to starter fertiliser and determine the optimum placement of fertiliser to evaluate the impacts on emergence, plant development, disease resistance, lodging and responses in relation to P retentiveness of soils