Key Points
- Weather records for Manawatu were analysed to determine the size and frequency of rainfall events that might cause leaching of fertiliser N applied to maize crops. This was supplemented with soil mineral N measurements in paddocks under different land uses.
- In the wettest season experienced over the past 35 years, fertiliser N applied 28 days after sowing (DAS) would not have moved below 1m until the following winter, well after crop N uptake of the fertiliser N.
- There was no difference in soil mineral nitrogen to 1.80 m in long-term maize and long-pasture paddocks.
- Soil nitrogen budgets show that growers are generally matching fertiliser input to crop uptake, but growers should take into account mineralisation of organic matter when determining N fertiliser rates for paddocks converting to maize from long-term pasture.