soil compaction in vineyards is due to the passage of machinery, especially if it is heavy and the soil is wet and clay-textured. Vineyards are particularly prone to compaction because tractor wheel tracks are confined to narrow strips, often in close proximity to the vine row. The soil is compressed so that the surface absorbs less water and soil pores are destroyed, and the supply of air and water to vine roots is diminished (see soil structure). Further, soil strength is increased, providing a physical barrier to root growth and earthworm activity. Soil compaction can reduce vine vigour and thus yield, and, in some instances, wine quality. Soil compaction, which may be the most serious environmental damage done in many vineyards, can be reduced by avoiding the use of heavy machinery on wet soils, and by using tracked rather than wheeled vehicles. Horse-drawn equipment is both a more traditional—and modern—alternative.