Cotton Lint Yields and Soil Phosphorus levels as Influenced by Long-term Poultry Litter Application, Conservation Tillage and Winter Rye Cover Cropping.

Repeated application of poultry litter to crop lands may lead to build up of phosphorus in surface soil which is prone to loss from runoff and erosion. Hence a long-term experiment was conducted at north Alabama to evaluate the poultry litter on cotton lint yields and to study build up of soil P. Treatments were established in 1996 on a Decatur silt loam and consisted of conventional-tillage (CT), mulch-tillage (MT), and no-tillage (NT) systems with winter rye cover cropping and ammonium nitrate (AN) and poultry litter (PL) as nitrogen sources. On average, NT recorded 22% higher lint yields than that of CT under cotton-rye cropping system (CR). But under cotton-fallow cropping system (CF), CT recorded 18% higher yields than NT. In CT plots lint yields did not differ with either of the N sources at 100 kg N ha^-1. But under NT system, on average, plots that received 100 kg N ha^-1 as AN recorded 15% significantly higher lint yield compared to PL at the same rate. All tillage systems gave similar lint yields when received AN @100 kg N ha^-1. However, CT plots which received PL @ 100 kg N ha^-1, gave similar yields compared to MT and similar or higher lint yields compared to NT system. Available phosphorus concentration of top soil (0-15cm) was significantly influenced by tillage and nitrogen source interactions. NT plots receiving PL @ 100 kg N ha^-1 recorded significantly lower available P at 0-5 cm (43 mg/kg) and 5-15 cm (27 mg/kg) depths compared to CT plots receiving PL at the same rate (75 and 36 mg/kg, respectively). These results show that poultry litter application under conservation tillage system and winter rye cover cropping is suitable for cotton production and helps in safe disposal of poultry litter.