It has been said by soil scientists that, by working the soil, it is possible to do in a few years what would take nature thousands of years to accomplish. Intensive soil cultivation and the addition of proper soil amendments can aggregate sandy soil to give it more crumb, or open heavy lime marl to give it more porosity. In both instances, when the proper soil consistency is maintained, the soil is said to have heart.
Among soils, only alluvial clay loams have this heart naturally. Clay is the heart of heart in the soil. But, as it is with everything in nature, there can be too much of a good thing. To much clay can produce a dense, sour soil in which water stagnates in puddles, plants rot from the roots, and growth is slow and uncertain, especially during cool seasons. Heavy clay heats up slowly. And if it ever dries out, it takes a concerted effort to penetrate it with water, since clay tends to shed water rather than absorb it when dry.
All things being equal, however, clay has a great potential to establish heart in the soil since it is absorptive, plastic, and chemically dynamic, when trying to overcome soil deficiencies.
A gardener has a bit of an advantage over a farmer, if the clay soil is truly impervious. A farmer deals with clay in selecting rotations of plants, which can pulverize the soil and break up the clods. In the west, where alkalinity also works against soil porosity, gypsum is often added because its sulfur content connected to the calcium (lime) brings the pH closer to neutral. This encourages heart in clay. Through proper plant rotations, as well as the application of rock powders, compost, and very careful tillage, a farmer can turn clay into soil in a number of years.
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