Technical Abstract: The most successful aquaculture enterprise in the U.S. is channel catfish Ictalurus punctatus production. In the U.S., 257 million kg of channel catfish were sold in 2007 at a value of $455 million. Large-scale commercial channel catfish culture began in the late 1950s and expanded rapidly from 1978 through 1990. About 70% of the catfish industry is localized in northwest Mississippi in the Yazoo-Mississippi River floodplain. Soils in this area consist of 50-60% montmorillonite clay, 30-40% silt, and less than 5% sand. Channel catfish production can be divided into four different phases: 1) broodstock, 2) hatchery, 3) nursery, and 4) grow-out. Some farms employ all production phases, while others concentrate on just fingerling production or grow-out. Fertilization strategies, therefore, depend on the production phase in question.