Measuring real time nitrate leaching from a tile drained Hawkes Bay onion field: Final report

The data showed a strong linear relationship between the N concentration measured by the sensor and in the grab sample (sensor N concentration = 1.09 × grab sample N concentration + 0.14, R2 of 97%). This indicates that the sensor can provide a good indication of sump nitrate-N concentrations, and that with calibration the accuracy can be improved further. The ability to measure real-time nitrate concentrations in the drainage water provided data that showed clear links between management practices, rainfall events and N leaching. Both modelling and real-time data also showed that modified agricultural practices, such as the use of catch crops, could reduce nitrate losses to ground water.