Risk assessment of Nitrogen and Phosphorus transfer after manure land application: a review of the main influencing parameters

International audience; The two major pathways of N and P loss from a plot of land receiving manure to water resources are leaching and runoff. The risks of contamination of surface water by runoff are associated to the sensitivity of the plot to runoff and N, P availability/mobility during runoff which depends on the rate of manure applied, climatic conditions, application technique and soil conditions (humidity,…). N, P loss by runoff following manure spreading could be strong in winter, spring and summer during heavy rainfall. Therefore the risk of transfer by runoff should be defined according to the cover of the plot rather than the application period. However, the likelihood that runoff water reaches rivers is not clearly established as it also depends on various parameters (plot characteristics, distance to river, tillage,…).. The water contamination due to infiltration is also complex with the same rage of factors influencing runoff loss. In addition, leaching loss is also related to nutrient cycling and their transport through the soil profile.