The installation and operation costs of drip irrigation systems can be reduced if the systems are designed using a lower uniformity. However, it remains unclear whether a lower system uniformity will result in a decreased crop yield and product quality in arid regions. Field experiments were conducted in arid environments in the 2010 and 2011 growing seasons of cotton (Gossypium hirsutum L.) to evaluate the effects of system uniformity on plant growth, nitrogen uptake, and lint yield and quality. In the experiments, three Christiansen uniformity coefficients (CU) for irrigation of approximately 65, 80, and 95% (referred to as low, medium, and high uniformity, respectively) and three irrigation levels of 50%, 75%, and 100% of full irrigation (referred to as low, medium, and high irrigation level, respectively) were used. During both seasons, a great decrease in the CU for plant height and leaf area index was observed for the low and medium uniformity treatments, while a slight increase in the CU was observed for the high uniformity treatment. System uniformity imposed an insignificant influence on the mean values of plant height, leaf area index, nitrogen uptake, and quality parameters, but a lower system uniformity significantly reduced the CU for plant height, leaf area index, nitrogen uptake, and lint yield. The influence of system uniformity on lint yield was related to the level of irrigation and the favorability of weather conditions for obtaining the potential yield. When the weather conditions (e.g., temperature) were favorable for crop growth, the low system uniformity treatment produced a significantly lower lint yield than the medium and high uniformity treatments at the full irrigation level. The interactive effects of system uniformity and irrigation level on crop growth and lint quality were insignificant. In arid regions, a CU value of around 80% could be used as the target uniformity of drip irrigation system.
