Technical Abstract: Poultry litter is a rich source of nearly all essential plant nutrients. It is generated in large quantities in the same southeastern US states where cotton is a dominant field crop but is rarely used as a primary cotton fertilizer partly because of lack of precise management recommendations. This research was conducted to determine what rates of broiler litter fertilization are adequate and whether supplementation with conventional inorganic N fertilizers would be necessary for optimum lint yield and quality under conventional and no-till production systems. The research was conducted from 2002 to 2004 on two commercial farms representing no-till (Coffeeville, MS) and conventional tillage (Cruger, MS). The treatments consisted of an unfertilized control, a farm standard fertilized with conventional fertilizers, and fresh broiler litter fertilization with rates of 2.2, 4.5, and 6.7 Mg ha-1 in an incomplete-factorial combination with 0, 34, or 67 kg ha-1 N as urea-ammonium nitrate solution (UAN) for a total of 10 treatments. Litter without supplemental UAN-N increased yield by up to 110 kg lint ha-1 for every 1 Mg ha-1 litter under both conventional and no-till production systems. The often recommended litter rate of 4.5 Mg ha-1 was not adequate to increase yield to be equivalent to that of the standard fertilization with conventional fertilizers. It was necessary to supplement this or the other litter rates with UAN-N to support yields equal to or greater than the yield of the farm standard. The most consistently well-performing fertilization at both locations in all years was the 4.5 Mg ha-1 litter supplemented with 67 kg ha-1 UAN-N. Lint yield was highly correlated with applied total plant available N (NTPA) which was estimated as the sum of 50% of analytically-determined litter N and 100% of UAN-N. Fiber quality, fiber length and micronaire in particular, also responded to NTPA, but the responses were smaller than lint yield. Litter when adequately supplemented with UAN-N did not adversely affect fiber quality. Only litter treatments (± supplemental UAN-N) that did not provide adequate N for lint yield negatively affected fiber length and micronaire. These results show that broiler litter, under both no-till and conventional tillage systems, should be supplemented with conventional N fertilizers when used at rates as low as 4.5 Mg ha-1 when the no-till yield target is ~1500 kg ha-1 and the conventional yield target is ~1700 kg ha-1).