Soil is comprised of mineral or organic soil particles with spaces called “pore space”. This space contains varying amounts of air and water depending on soil type and conditions. The ratio of particle to pore space would ideally be 50:50 in natural un-compacted friable soils. However for most soils the reality is very different. The demands of grazing and the regular use of machinery, often in wet and highly unfavourable conditions, is very destructive to soil structure. Intensive stocking on wet soils can 'pugging' in paddocks, and heavy machinery can result in soil compaction. Either of these conditions can cause poor drainage, poor plant growth, greater fertiliser requirements and more topsoil and contaminant runoff to waterways.
Soil compaction starts at the surface and builds progressively throughout the soil profile often to considerable depths, preventing water penetration and the movement and up-take of all essential elements. As the soil particles pack closer and closer together pore space is eliminated and the soil becomes devoid of air and water, thus denying grass plants the “essentials of life”.