The most significant limiting factor for sustained or improved production of cotton particularly in the Texas High Plains is the timely availability of water. One method for water application for cotton production that has increased in recent years is sub-surface drip irrigation (SDI). It has been estimated that approximately 250,000 acres of cotton is currently irrigated by SDI on the Texas High Plains. Since the interaction between the rate of crop development and water application by SDI in terms of maximizing productivity is unclear, a series of field studies were conducted using different water applications based on a range of irrigation well capacities to determine seasonal water use, root system distribution and crop yields. The results indicated significant differences in crop yields that were directly related to the amount of water applied. However, the yield increase was not linear particularly at the higher water application levels. There was increased root development at the lower soil depths (80-100 cm) as the season progressed as was the increase in root concentration in proximity to the buried drip lines.