Soil Organic Matter and Nutrient Levels in Outdoor Runs in Organic Laying Farms

To evaluate the nutrient load due to the grazing of laying hens in outdoor runs, monitor- ing of soil characteristics was carried out in three organic Italian farms. For each farm, soil samples were taken from three increasing distances from the hen house and two depths and different chem- ical parameters were evaluated. The comparison among the results from the different distances show that N-NO3 and Olsen P are the most affected parameters by hen feaces: both present high values with a statistically significant difference in the area close to the poultry house and for the most superficial layer. Even TKN and TOC show significant differences between the concentrations of the first layer (more concentrated) and those of the second layer (less concentrated). In general, the surface soil layer closest to the chicken house is the portion of the outdoor run most affected by chicken droppings and represents the most critical point in terms of potential environ- mental impact. Therefore, it is necessary to intensify the management of the outdoor run with tools that can facilitate the grazing of animals and with vegetation that can absorb nutrients by limiting leaching and run-off. Keywords: free-range system; hen runs; nitrogen; phosphorus; organic matter.