Factors affecting arsenic and copper runoff from fields fertilized with poultry litter.

Arsenic (As) and copper (Cu) runoff from fields fertilized with poultry litter has received increasing attention in recent years, although it is not known if heavy metal runoff from poultry litter poses a significant threat to the environment. The objective of this study was to determine the main factors affecting As and Cu concentrations in runoff water from pastures receiving poultry litter applications. Rainfall simulation studies were conducted to determine the effects of the following treatments on metal runoff: (i) aluminum sulfate (alum) additions, (ii) diet modification using phytase or high available phosphorus corn, (iii) fertilizer type, (iv) poultry litter application rate, and (v) time until the first runoff event occurs after poultry litter application. Results showed that alum additions to poultry litter significantly decreased As and Cu concentrations in runoff water. Copper concentrations were highest in runoff from poultry litter from birds fed phytase diets compared with other diets; however, this effect may have been a result of wet storage conditions rather than diet. Triple superphosphate applications resulted in the lowest heavy metal concentrations in runoff water among all fertilizer treatments, while normal poultry litter resulted in the highest concentrations. Arsenic and Cu concentrations increased in runoff water as poultry litter application rates increased and decreased with increasing time until the first runoff event. These data indicate that adding alum to poultry litter, a cost-effective best management practice, which also results in lower P runoff and ammonia emissions, may also be an effective tool in reducing metal runoff.