Traditionally fed outdoor sows at commercial stocking rates can deposit onto soil in excess of 500 kg of nitrogen per hectare per annum from unused dietary nutrients. This has the potential to give rise to serious environmental pollution problems, and it is therefore important to seek methods to reduce this amount or to influence its pollution potential. One major determinant will be the extent to which it can be captured and utilised in grass growth, but this will be dependant on the extent to which the rooting activity of the pigs has destroyed the vegetation cover. This experiment was therefore designed to measure the impact of reducing dietary nitrogen inputs and maintaining grass cover by nose-ringing of sows on the long term changes in soil nitrogen content.