When adding a wintering pad, there is typically a decrease in N leaching from urine as less is being deposited on the pasture, but an increase in background N leaching is possible due to increased effluent applications. The relative effects depend on the timing animals are placed on wintering pads, and the way the effluent is managed.
Generally placing animals on wintering pads, especially in late autumn/early winter, results in decreased leaching, and this decrease is larger if deferred application of effluent is also practiced.