The Southern High Plains of Texas plants between 3.5 to 4.0 million acres of cotton annually, representing the largest cotton production region in the world. To plant this acreage approximately 70 to 80 million pounds of cottonseed are needed; all of which is grown on the High Plains. Due to the large amount of seed required, the increased use of transgenics, and associated high costs, maximizing seed quality has become a concern. Water supply, growing season length, and nutrient supply are the major limiting factors to cotton production in this region. Cotton will utilize between 20-22 inches water throughout the growing season. With an average rainfall of 18 inches yr^-1, water must be supplemented to the developing crop to maximize production. The prevailing temperatures are characterized by marginal heat unit accumulation during the early and latter parts of the growing season. The cool temperatures in September and October limit the maturation of both the seed and fiber of bolls resulting from flowers in mid-August. The nutrient supply, highly controlled by the producer, represents the final limitation to production of cotton on the High Plains. Nutrient management can affect rate of crop maturity, as well as, water use efficiency. Because of this, more efficient nutrient management strategies, particularly N and P, are needed to maximize seed production as governed by water supply and heat unit accumulation. The soil conditions on the Southern High Plains results in very low quantities of soluble P available to the growing plants (high soil pH, >7.6, and high quantities of CaCO₃). Supplying a balanced blend of nutrients through the irrigation water during the early fruiting period will increase the soluble P fraction and reduce the potential for P limiting fruit retention and seed growth rates resulting in more seed of the highest quality. This study compared different methods of phosphorus application (no phosphorus, pre-plant, sidedress, fertigation) and evaluated the effect that each had upon seed production and quality. This study also compared the ratio of N: P and established the most optimal rate of fertigation to maximize seed production and quality. The N: P ratios are 5:0, 5:1, 5:2, and 5:3 (# N: # P₂O₅) per inch of irrigation water. Three years of data indicate that fertigation is an acceptable method producing the greatest seed yields with adequate seed indexes and seed density. The ratio of N: P indicates that with increasing levels of irrigation more P is required. Through the use of fertigation, producers will be able to manage nutrient inputs as governed by the growing season and yield potential.