Impact of conservation tillage and nutrient management on soil water and yield of cotton fertilized with poultry litter or ammonium nitrate in the Georgia Piedmont

Cotton has become a dominant crop in the southeastern USA, but only about 12% of the 620,000 ha of cotton (Gossipium hirsutum L.) in Georgia, for example, is under conservation tillage. Georgia and bordering states produce about 42% of the poultry in the United States and in Georgia alone, this results in over 1.6 million Mg of poultry litter (PL) annually. The fertilizer value of PL is well-recognized but much of it is applied to pastures and only a small percentage is applied to crop land. Limited information is available on the response of cotton to PL as fertilizer in conservation tillage systems in the Southeast. The performance of cotton under two tillage and two fertilizer treatments was evaluated from 1996 to 1999 to highlight management options for increased adoption of conservation tillage and PL use. Cotton, followed by a rye (Secale cereale L.) cover crop, was grown under a factorial arrangement of tillage (no-till (NT) vs conventional tillage (CT)) and fertilizer (ammonium nitrate, as conventional fertilizer (CF) vs PL) on a Cecil sandy loam (clayey, kaolinitic thermic Typic Kanhapludult; Chromi-Alumic Acrisol) near Watkinsville, Georgia. Average lint yield from 1996 to 1999 was in the sequence no-tillpoultrylitter (NTPL)>no-tillconventionalfertilizer (NTCF)>conventionaltillagepoultrylitter (CTPL)>conventionaltillageandfertilizer (CTCF). Differences were significant at P <or= 0.05 for NTPL vs CTPL, NTPL vs CTCF, and NTCF vs CTCF. Average yield differences were also significant between NT and CT but not PL and CF. PL yielded more than CF only in 1997. NT generally had a more favorable soil water regime than CT. Yield differences among treatments occurred during the first 3 years only. Drought in the fourth year reduced yield across all treatments and negated treatment effects. Lint yield would increase in the southeastern USA and an additional outlet for the PL would be created by adopting NT and fertilizing with PL in cotton production.