The NO3‐‐N concentration in saturation extracts and soil solutions was determined in 30‐m profiles in six treatments of a longterm fertility trial with citrus and in four commercial citrus groves in which the depth of sampling was 15 m or to the top of the water table.Drainage volumes and excess N in the soil, calculated as N input minus crop removal, provided a reasonable estimate of the NO3‐ concentration of water in the unsaturated zone in open‐porous soils when inputs were about 150 kg/ha per year. However, at higher rates of inputs to porous soils or at low rates with soils with profiles which had textural discontinuities, denitrification had to be assumed to obtain a reasonable N balance. Calculated transit times for water to move 30 m in the unsaturated zone varied from 12 to 49 years.