Nitrogen leaching from tile-drained fields and lysimeters receiving contrasting rates and sources of nitrogen

Leaching of nitrogen from arable land can lead to pollution of groundwater and surface water. Various measures have been implemented in agriculture to reduce leaching, but there is still potential to do more. To find the best agricultural management regime to limit the problem, leaching from soils under different management must be measured. Different methods to estimate leaching are available, but they have not been thoroughly evaluated. This study compared (a) leaching of nitrogen from five different fertilizer treatments differing in amount and source (mineral and organic) of nitrogen and (b) two different methods for measuring leaching (tile-drained field plots and lysimeters). Nitrogen leaching from five different fertilizer treatments was studied for three years in a tile-drained field facility and for three of the treatments also for 16 months in a lysimeter facility. Leaching from organic and mineral nitrogen sources was similar in the three-year field study. Mineral nitrogen input above the economic optimum tended to give greater leaching (by 24%–43%) than nitrogen input at the expected optimum. Measurements in lysimeters and tile-drained field plots gave similar results, although leaching values tended to be slightly higher (by 18%–25%) in the tile-drained field. Overall, both facilities give reliable estimates of nitrogen leaching and are suitable for leaching studies.