Key Points
- Two experiments were conducted to investigate the impacts of early season N leaching
- Irrigation was used to induce leaching under various fertiliser regimes applied to a maize crop
- Yields were unaffected by irrigation as high rates of N fertiliser were used
- Excessive irrigation altered the distribution on soil mineral N but not the total amount in the sampling depth (180cm)
- Fertiliser N remained within the rooting zone of the maize crop (180cm)
- Calculations of N movement corresponded with field measurements
- If N has moved to depth, a shallow soil sample (15cm) may underestimate soil N availability
- Two new projects will investigate the long term effects of N movement and the use of deeper soil sampling to improve estimates of soil N availability