A shovel, spade, garden fork or rototiller mechanically modifies soil. Dig or till when soil is neither too wet nor too dry. It can result from improper digging or tilling. When preparing to install a lawn or garden, avoid use of heavy machinery. Rototill only when necessary.
Observation shows that earth worms leave rototilled soil.
Both factors have a negative impact upon the overall quality of garden soil. Digging in or walking on wet soils causes compaction. Once organic matter has been tilled into the soil, keep off the soil. Use paths or lay down boards that distribute weight more evenly over an area. A good rule is to work the soil no more than necessary to achieve desired soil structure.