Key Points
- Weather records from Whakatane were analysed to determine the size and frequency of rainfall events that might cause leaching of fertiliser N applied to maize crops. Drainage losses below 1m were calculated for the wettest season (2001-02) and less extreme seasons.
- Fertiliser N applied at sowing has some risk of moving below 1m during the growing season, but on average that is not likely to occur until 220 days after application.
- Around Whakatane, growers should split fertiliser N applications to maximise the chance of the crop taking up all the fertiliser N, and minimise leaching losses.
- Substantial drainage is likely over winter so growers should only apply as much fertiliser as required after the existing soil N pool is accounted for.