A joint project of the USDA-ARS and University of CA was conducted over a four year period to assess growth, yield and nitrogen (N) uptake responses of cotton to a range of nitrogen applications under subsurface drip irrigation. This investigation is part of a series of field studies underway to identify potential for better plant responses and reduced groundwater NO₃-N contamination through use of alternative management practices such as frequent, low-dose applications under drip irrigation, split N applications, reduced preplant N and/or lower total N applications Plants were grown under subsurface drip irrigation and irrigated daily to avoid water deficits. Phosphorus, potassium as well as nitrogen fertilizers were injected into the water. Nitrogen treatments were 0, 60, 120 or 180 kg N per hectare (ha) combined with pre-plant applications of 0 or approximately 53 to 56 kg N per ha. Soil NO₃-N levels in the upper 1.2 m of the soil profile were in the 10 to 30 mg N0₃-N/kg range in the first and second years of the study. In the third and fourth year, soil N levels were significantly lower, and petiole nitrate-N levels in 120 kg and lower N application treatments were in the borderline deficient or deficient range of University of CA recommendations for cotton. Peak yields (between 1600 and 2100 kg lint per ha) occurred in 120 and 180 kg N treatments, with no difference in yields with applications in excess of 120 kg N per ha except in the 120 kg treatment without pre-emergence supplemental N in the fourth year. Residual soil N levels have significantly influenced the response to amounts of applied N over the three years.