Water supply, growing season length, and nutrient supply limit cotton (Gossypium hirsutum) production on the Southern High Plains of Texas. Approximately one-half of the total cotton acreage in the area is capable of supplemental irrigation however, the supply is usually considerably less than the demand and deficit water management is common. Irrigation management is often limited by available water quantity that cannot be controlled by the producer. The use of LEPA (low energy precision application) rather than spray application of the irrigation water is becoming more widely adapted because of reduced evaporation losses of water. Growing season length is limited by heat unit accumulation rather than frost-free days with both cool springs and falls common. The major factor left to the producer's control is fertility. Fertility management can affect fruit retention and boll size of cotton, which can affect water use efficiency. Nitrogen requirements and application timing relative to the water supply has clearly been established for the region. The development of more efficient phosphorus management strategies is needed to maximize use of all available resources in cotton production. The main concern of phosphorus fertilization is that the soil system has a high pH and abundant free calcium that forms insoluble calcium phosphates that limit phosphorus availability to cotton. Applying multiple applications of a balanced nutrient blend in small amounts through the irrigation water during the time of peak crop use will increase phosphorus availability and maximize use efficiency of water and other nutrients. This study compared different methods of phosphorus application (no phosphorus, pre-plant, sidedress, and fertigation) to determine if there is a real difference in the plant response to the application methods. The ratio of nitrogen:phosphorus was compared to determine which phosphorus level is most effective through fertigation. The ratios were 5:0, 5:1, 5:2, and 5:3 (lb. N:lb P₂O₅) per inch of total water. In three years of research we have found that fertigation is an acceptable method of applying phosphorus to the cotton crop and that higher phosphorus ratios give a yield response through more lint per boll. Using fertigation as an application method will give producers the opportunity to manage their fertilizer inputs based on in season yield potential saving them both time and money.