Publisher's Synopsis
Excerpt from Surface Formations and Agricultural Conditions of the South Half of Minnesota
Soil is the loose unconsolidated material which nearly everywhere covers the surface of the earth and in which plant life may be maintained. It is made up of finely divided rock in which decaying vegetable matter and animal matter are mingled. A soil is generally in a state of change. It is being washed little by little to the creeks and rivers which carry it to the sea, where it often forms delta deposits; if no new soil formed, hard rock would finally be exposed instead of the loose plant-producing soil. But rocks at and near the surface are continually changing and new soil is being formed from the underlying rock or from loose clayey or gravelly material that may constitute the subsoil, or from bowldery material that at many places in Minnesota lies between the hard rock and the soil.
Water and air attack rock matter and break it down. Heat and cold, freezing and thawing, shatter the rocks and give plants an Opportunity to send roots into the cracks that are formed, and these, prying the rocks apart, reduce them to particles of still smaller size. Even the hard solid rocks are ultimately broken down; a building of good solid stone may crumble in a few hundred years, especially in a moist climate.
Some of the rocky matter is dissolved by the water and carried to the sea in solution. It is such dissolved material that makes water hard and that gathers in the bottom of a vessel when water is boiled. But not all of the soluble substances are dissolved and carried away; some remain in the soil, and the character of the soil depends largely upon these. Some soils are acid because they have not enough lime. Some are deficient in potash or phosphates, which are necessary if soil is to produce certain crops satisfactorily.
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