Key Points
- Weather records for the Waikato region were analysed to determine the size and frequency of rainfall events that might cause leaching of fertiliser N applied to maize crops.
- The wettest months are in winter, with large rainfall events uncommon.
- Long duration rainfall events (5+ days) are more common during winter (20%) and spring (12%) than summer (6%), making timely operations often difficult.
- In the wettest season, fertiliser N applied at sowing would not have moved below 1m until late May, by which stage the crop would have taken up all the fertiliser N.
- The results from the case study simulation matched those found in a leaching study carried out in the same season.
- Provided appropriate fertiliser N rates are used, the Waikato region has a low risk of fertiliser N leaching, therefore it is possible to apply a greater proportion of fertiliser N before or at sowing.