Impact of excreted nitrogen by grazing cattle on nitrate leaching

Data from the De Marke experimental farm on water and nitrogen flows in two grazed pastures were used for model calibration and validation. The irregular distribution of excreta was used for a simulation study quantifying the variability of nitrate-N concentrations. The resulting simulated distribution explained the average and peak values of the measured concentrations. Temporal variability (weather) was used to assess the nitrate leaching risk under urine patches. At Site A the probability of exceeding the EC directive for drinking water under a urination deposited in either July or September was 10 and 25% respectively, and at Site B this was always 100%