Rainfed farming is very difficult because vertisols can be worked only under a very narrow range of moisture conditions : they are very hard when dry and very sticky when wet.
22.
Sugarcane can be grown on many soils ranging from highly fertile well-drained mollisols, through heavy cracking vertisols, infertile acid oxisols, peaty histosols, to rocky andisols.
23.
Some, known as " crusty vertisols ", have a thin, hard crust when dry that can persist for two to three years before they have crumbled enough to permit seeding.
24.
Vertisols are not extensive in the US, being confined to areas where there is a great abundance of swelling clays, e . g . montmorillonite, that cause churning of soils as a consequence of wetting and drying cycles.
25.
With the aid of X-ray diffraction, paleosols can now be classified into one of the 12 orders of Soil Taxonomy ( Oxisols, Ultisols, Alfisols, Mollisols, Spodosols, Aridisols, Entisols, Inceptisols, Gelisols, Histosols, Vertisols and Andisols ).
26.
Alternate shrinking and swelling causes " self-mulching ", where the soil material consistently mixes itself, causing vertisols to have an extremely deep A horizon and no B horizon . ( A soil with no B horizon is called an " A / C soil " ).
27.
Major areas where vertisols are dominant are eastern Australia ( especially inland Queensland and New South Wales ), the Deccan Plateau of India, and parts of southern Sudan, Ethiopia, Kenya, and Chad ( the " Gezira " ), and the lower Paran?River in South America.
28.
Wilkinson and Humphreys offer evidence that bioturbation appears to be the most active pedogenic process operating in many soils . While probably close to the mark, research over multiple decades strongly indicates that bioturbation is the dominant process in the upper part of most soils, notable exceptions possibly being vertisols and cryosols, where shrink-swell and freeze-thaw processes, respectively, appear dominant.
