Assessment of nitrogen and phosphorus loads present in environments impacted by alternative poultry processing operations utilized in pasture-raised poultry production

Pasture-raised poultry (PP) production systems allow chickens, turkeys or other poultry types to be raised entirely on pasture or in small, open-air moveable pens with access to fresh pasture daily. With an increase in consumer demand for poultry products produced using more humane and potentially environmentally sustainable practices, PP production systems are regaining popularity among farmers across the USA. The majority of research on PP is related to meat quality and forage conditions while the environmental effects have remained largely unstudied. The rotation of poultry on pasture is one of the primary best management practices (BMP) used to avoid over grazing and buildup of excess nutrients and pathogens; however, BMPs for handling and processing of the associated wastes (i.e., wastewater, feathers, offal) related to on-farm processing and mobile poultry processing units (MPPU) are not as well established. Therefore, a study with PP growers in the southern USA was initiated to provide important baseline information on the potential environmental impacts of processing methods used by PP production systems. Here, three farms utilizing on farm processing were sampled over a 9-month period and two farms utilizing a MPPU pilot plant were sampled over a 3-month period. Soil, compost and wastewater samples were collected during each sampling date for on-farm processing while only wastewater was collected at the MPPU pilot plant. Soil samples (24-cm cores) were analyzed for total nitrogen (TN), Mehlich-3 extractable phosphorus (M3-P) and moisture content. Compost derived from processing wastes was analyzed for TN, total phosphorus (TP), water extractable P and moisture content. Wastewaters were analyzed for total Kjeldahl nitrogen (TKN) and TP. Soil TN levels (0.075-0.30%) reported here are comparable with TN levels reported for various soils in the Southeastern USA while M3-P was generally below levels found in agricultural soils subject to conventional poultry litter application based on previously published data. Conversely, TN and TP levels -0.3 to 1.3 and < 0.4%, respectively-in compost were well below recommended values (i.e., approximately 2% each of N and P) for compost highlighting an opportunity for PP growers to create a more useful compost for land application. Last, wastewater collected from both, on-farm processing and the MPPU measure TKN and TP levels were much less than conventional processing. Overall, the present study provided baseline data on soil and compost nutrients related to on-farm poultry processing as well as wastewater composition for on-farm processing and MPPUs.