improve local drainage and promote the proliferation of earth worms that can, over time, break relatively thin hardpan layers. More difficult hardpans may be further improved through the action of both adjusting the soil pH with lime if the soil is acidic, and with the addition of gypsum. This combination can help loosen clay particles bound into a hardpan by the actions of hard salts such as iron, calcium carbonate and sodium, by promoting their mobility through a higher pH while proving a suitable source of exchanging minerals (the gypsum). This works because gypsum salts, although not "soft", are still water permeable and have a larger, more open structure, the results of which do not promote as hard a matrix as was replaced. However, unlike when employing mechanical means, breaking a hardpan through the use of amendments may require action over the course of years, and even then one is by no means assured success. The results are primarily determined by how extensive and / or intractable the hardpan is. See also Caliche Claypan Duricrust Duripan Fragipan References Soil Pedology