Tillage is the act of disturbing the soil through some type of mechanical means. It has been practiced since the development of crude instruments such as a pointed stick to create a hole into which a seed was dropped. The largest advance in the progress of tillage implements has been the invention of the moldboard plow, which inverts the soil and allows rapid cultiva- tion. Since that invention, there have been continual advances in the development of tillage equipment for the purposes of: creating a seed bed that is favorable for rapid germination; removing weeds; destroying crusts that impede the emergence of seedlings, or prevent water or gases from moving into or out of the soil; or removing compacted layers from the upper soil profile. There is a large array of tillage tools available to producers that reshape the soil into a more compliant medium for producing plants.
Tillage can be considered as a time-and-space op- eration within a given field. The time component is introduced because different tillage implements are used throughout a production sequence to achieve different goals in manipulating the soil profile. The space component is introduced because different till- age implements affect the soil in a variety of ways
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across a field. An example of this is that the preplant tillage operation often disturbs the entire soil surface, while cultivation only disturbs the area between the rows of plants. An entire production sequence can be considered as a series of tillage operations that changes the soil surface in different ways.
Zone tillage is a unique subset of tillage oper- ations in which only a portion of the soil surface is disturbed. In a very broad sense, zone tillage can be considered to represent cropping in which strips of the field are planted to different crops and managed differently or a strip is left in a fallow area to conserve precipitation for the subsequent crop. In the Great Plains of the USA and the Prairie provinces of Canada, the practice of strip farming with cultivated and fallow strips could be considered as a large-scale form of zone tillage. In this case, the zone is created by the temporal distribution of tillage operations in which strips of the field are cultivated one year and the next year the fallow strip is cultivated.