Lint Yield and Fiber Quality of Cotton Fertilized with Broiler Litter

Poultry litter is generated in large quantities in the same southeastern U.S. states where cotton (Gossypium hirsutum L.) is a dominant field crop, but is rarely used as a primary cotton fertilizer partly because of lack of adequate management recommendations. This research was conducted to determine adequate rates of broiler litter and whether supplementation with inorganic N would be necessary for optimum cotton lint yield and fiber quality. The research was conducted from 2002 to 2004 on two commercial farms representing conventional-till (CT) and no-till (NT) systems. The treatments consisted of an unfertilized control, a farm standard (STD) fertilized with inorganic fertilizers, and broiler litter 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). Litter without supplemental UAN-N increased yield by 23 to 110 kg lint ha^-1 for every 1.0 Mg ha^-1 litter under both CT and NT. The often-recommended litter rate of 4.5 Mg ha^-1 was not adequate to increase yield to be equivalent to that of the STD that received 101 to 135 kg ha^-1 as UAN. It was necessary to supplement this or the other litter rates with 34 or 67 kg ha^-1 UAN-N to support yield equal to or greater than the yield of the STD. The most consistently well-performing treatment under both tillage systems in all years was the 4.5 Mg ha-1 litter supplemented with 67 kg ha^-1 UAN-N. Lint yield was highly correlated (r^2 = 0.83-0.97) with applied total plant-available N (NTPA) under both systems. 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. These results show broiler litter as much as 4.5 Mg ha^-1 should be supplemented with inorganic N fertilizers when used as a primary cotton fertilizer and when the expected yield is (almost equal)1700 kg ha^-1 under CT and (almost equal) 1500 kg ha^-1 under NT.