Effects of management options for grazing cattle within dairy farming

On an experimental farm, water and nitrogen flows in the unsaturated zone have been monitored at two grazed permanent grassland plots since 1991, providing a basis for validating simulation models. High variability of nitrate-N concentrations was probably caused by uneven spreading of unrine and dung patches during grazing. Simulation studies with grazing options showed that high concentrations in the field could be explained by these options. Urine patches occurring later in the growing season gave higher concntrations with a more pronounced effect in the second year. In a relatively wet field, effective grazing management might keep nitrate-N concentrations below 11.3 mg/l (EU directive), but in the drier field other measures will be necessary