Why are regur soils capable of sustaining moisture sufficiently for a long time?
Answers
Among the in situ soils of India, the black soils found in the lava-covered areas are the most conspicuous. Those soils are often referred to as regur but are popularly known as “black cotton soils,” since cotton has been the most common traditional crop in areas where they are found. Black soils are derivatives of trap lava and are spread mostly across interior Gujarat, Maharashtra, Karnataka, and Madhya Pradesh on the Deccan lava plateau and the Malwa Plateau, where there is both moderate rainfall and underlying basaltic rock. Because of their high clay content, black soils develop wide cracks during the dry season, but their iron-rich granular structure makes them resistant to wind and water erosion. They are poor in humus yet highly moisture-retentive, thus responding well to irrigation. Those soils are also found on many peripheral tracts where the underlying basalt has been shifted from its original location by fluvial processes. The sifting has only led to an increased concentration of clastic contents.
Answer:
They have rich content of calcium carbonate , magnesium , potash and lime but the phosphorous content is poor.