Stochastic approach to assess a nitrateprocess-factor in soil water

A process-factor was driven for the NO^- 3 -N concentration in the soil water. The processfactor was calculated to a catchment in Belgium. The NO^- 3 -N concentration in the surface water at the outlet of the catchment was used as Cs. The model was run on each individual field within the catchment for four consecutive winter periods. A Monte Carlo approach was used (i.e. the simulation was repeated 1500 times with new picks from the NO^- 3 -N distribution functions on October 1st considering the crop rotation. The results indicated that, the process-factor, calculated as the ratio of the simulated NO^- 3 -N concentration in the soil water at 90 cm and the measured NO^- 3 -N concentration in the surface water, for the catchment is 2.35. Moreover, the proper management of crop nutrients (nutrient source, application rate and timing) is an important way to help control the loss of nutrients through surface runoff and subsurface drainage water.