The literature was reviewed for nitrate leaching under irrigation. The mass of nitrate leached is directly related to the percolation volume. Both water management and nitrogen managementareimportant in controlling nitrate leaching. Applying only enough nitrogen fertilizer to meet yield goals, timing of nitrogen application and the use of slow release fertilizers are nitrogen management practices that will reduce nitrate leaching. There have been a number of nitrogen simulation models that have been developed, but there is a lack of field data to validate the models.