Figure 1. Nitrogen rates where cotton is planted every year (Rates of N-P-K test) and cotton following soybean (Two-year Rotation experiment) at five Alabama locations, 1992-1998. Relative yield is the lint yield compared to the lint yield of a treatment receiving 90 pounds N per acre. All N is applied in split applications. Data in Fig. 1 is a compilation of average (mean) relative yields for N rates at each location and year. Relative yield is the percentage yield of each treatment compared to a standard N rates of 90 pounds per acre. Cotton crops on Coastal Plain soils appear to respond to N similarly and are combined into one curve with a near maximum yield at 90 pounds N per acre. Cotton crops on the finer textured soils of the Tennessee Valley (Decatur silty clay loam) reach a near maximum yield at 60 pounds N per acre, probably due to less leaching loss and some N retention.