Sugarcane is grown on over 20 million ha worldwide, and on nearly 400,000 ha in the United States. Substantial water is required to produce this high biomass crop, therefore when rainfall is limited irrigation is necessary. As population and industry expand, water for irrigation of agricultural crops becomes increasingly limited. Improved irrigation efficiency based on a fundamental understanding of crop water requirements and use under various conditions is increasingly important. Fertilization practices vary greatly depending on local conditions. However, substantial nitrogen inputs are almost always required to produce sugarcane. This work was conducted to determine whether water availability affects sugarcane nitrogen fertilization requirements, and whether N application affects responses to water stress. Field studies were conducted in semiarid South Texas on alluvial, calcareous, sandy clay loam soils. Sugarcane responses to N fertilization were minimal in first and second crops, indicating that adequate residual N was available, even though this was not evident in the soil testing. In later ratoon crops, responses to N fertilization increased, reflecting depletion of residual reserves. Decreasing water availability had little effect on sugarcane responses to N fertilization at low stress levels, but as water stress increased N fertilization responses declined. If water is limiting crop growth, N fertilization is of no use. N fertilization did not compensate or offset the effects of water stress.