Influence of organic chicken dejections on the soils of two contrasting outdoor-runs of AlterAviBio experimental facility: Ex-ante assessment of variations in C, N, P, Cu and Zn soil stocks

Organic broilers must have an access to an outdoor-run as specified in European Council regulations on organic farming. Yet, the impact of animals on the outdoor-run is unknown. The objective of this study was to estimate the influence of organic broiler production on the soils of two contrasting outdoor-runs (grassland vs. oak grove) regarding the stocks of C, N, P, Cu and Zn. 25 composite samples were composed for each outdoor-run. The initial stocks of C, N, P, Cu and Zn were determined for two horizons by measuring bulk density and total or available elements content. The excretion of C, N, P, Cu and Zn of broilers was estimated with French references and compared to detections thresholds calculated from initial stock values in order to determine whether significant stock variations could be detectable or not. C and N initial stocks vary correlatively in space and are higher in the oak grove soil. P stocks are important with a great spatial variability. Cu and Zn stocks are similar in both outdoorruns and beyond national standards. The theoretical variations in C, N and P stocks will be detectable whereas Cu and Zn stock variations will be not. The final actual stocks of C, N, P, Cu and Zn will be measured with the same method and compared to the results presented in this study.