Calcium naturally occurs in most soils around the globe. However, in temperate grasslands and deserts, soils form through calcification, or the process that leaves a large layer of calcium beneath the surface of the soil. In areas where agriculture and ranches have lead to land mismanagement, unintentional calcification can cause long-term problems. Does this Spark an idea?
Process
Calcium from lower layers of soil is pulled up by deep tap roots. As plants shed their leaves, the calcium in the leaves breaks back down and is leached through the soil during rainstorms. Compact soils don't leach calcium as readily as well-draining soil, such as soil high in organic matter. So when compact or frozen sublayers of soil lie under lighter soils, a layer of calcium builds up. This is known as calcification.
Problems
In agriculture, calcification may occur at levels in the soil too low for shallow-rooted plants to reach. Since most agricultural practices are monoculture, or the exact same crop over an entire field, this means the entire crop may show signs of calcium deficiency despite the fact that calcium is plentiful in the soil. If enough calcium deposits remain at the same level over long periods of time, it will form caliche, or hardpan. This layer of soil will keep water from seeping down into the soil, and will lock deeper-rooted plants away from nutrients lower in the soil.
Human Calcification
Humans contribute to calcification through constantly flood irrigating, overgrazing a field (putting too many animals on too small a field) or by using heavy machinery. For example, when a farmer floods his field, the surface calcium seeps down. Due to the sheer amount of water on the surface, the water drags many nutrients downward. They hit a slightly less permeable layer, and the calcium is left behind as water continues to try to move downward. Later, the farmer uses heavy machinery to till his fields. This creates further compaction deep in the soil, and leaves only the surface loose for plants to grow. A few years of this quickly forms hardpan.
Considerations
No-till methods and diversification of crops (using several different kinds of crops with several different root depths) can reverse some of the worst problems of calcification. As deeper rooted or taproot plants break up the hardpan, water follows the roots down deep into the soil at a more constant rate. The calcium moves back up to the surface when it is absorbed through the plant and deposited during leaf fall. Because that calcium is available to shallower-rooted plants, farmers or gardeners need not apply more calcium. As long as the farmer or gardener does not use heavy machinery in this area, eventually the hard-pan will break up and the calcium will re-distribute fairly evenly.
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