Ustic
Ustic Moisture Regime | |
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Semi-arid |
Ustic is a class of soil moisture regime. It is one of a range of different soil moisture regimes, such as: aquic moisture regime, aridic moisture regime, udic moisture regime and xeric moisture regime. The ustic moisture regime is intermediate between the aridic regime and the udic regime.[1]
Definition
The ustic moisture regime (Latin: ustus, burnt) applies to
Geography and Climate of Ustic Soils
There are certain climate conditions which characterises a particular soil as ustic: the soil temperature must be 22 °C (degrees Celsius) or above annually, or winter contra summer soil temperatures must vary by less than 6 °C at a particular depth of 50 cm below the soil surface. The soil moisture control section of ustic soil is dry, in some or most parts, for at least 90 or more cumulative days in a normal year. Ustic soil is also moist, in some parts, for more than 180 cumulative or 90 consecutive days per year.[2]
If the soil temperature is 22 °C and above annually, or if winter contra summer soil temperatures vary by more than 6 °C at a particular depth of 50 cm below the soil surface, the soil moisture control section of ustic soil is dry, in some or most parts, for at least 90 or more cumulative days in a normal year. Although it is not dry in all parts for more than half of these cumulative days, at a soil depth of 50 cm the soil temperature is greater than 5 °C. In the event that the moisture control section is moist in all parts for 45 or more consecutive days in the four months after the winter solstice, the moisture control section is then dry in all parts for less than 45 consecutive days in the four months after the summer solstice.[2]
Regions with an ustic soil moisture regime often experience erratic rainfall which mostly occurs during the growing season. Summer droughts are erratic, but frequent. Ustolls (soils characterized with the ustic soil moisture regime) are the most commonly occurring suborder of
The ustic soil moisture regime is also common in Central Africa (Zambia, Tanzania, Angola), in India, and in some countries of Eastern Europe and South America.[5]
Characteristics of Alternative Moisture Regimes
Soil Moisture regimes affects soil genesis (formation), and the usage and maintenance of soil condition, so they are used as a soil classification criterion for soils with similar properties and Morphology.[6] The following are the four other major soil moisture regimes:
Aquic (or Perudic)
Soils that have the aquic moisture regime are virtually free of dissolved
Udic
The soil moisture control section is not dry in any part for around 90 days in the udic moisture regime. The soil moisture control section becomes udic if the mean soil temperature is lower than 22 °C and the mean summer and winter soil temperatures (at a depth of 50 cm from the soil surface) differ by 6 °C or more, is dry in all parts for less than 45 consecutives days in the 4 months following the summer solstice. Soils that have an udic moisture regime commonly occur in areas of humid climates that have well distributed rainfall: i.e. they have adequate summer or winter rains, and generally cool summers.[1]
Aridic
The moisture control section in the aridic moisture regime is dry when the temperature of soil, at a depth of 50 cm from the soil surface, is above 5 °C for more than half of the cumulative days per year and moist when it’s above 8 °C for less than 90 consecutive days. Soils that have an aridic moisture regime normally occur in an
Xeric
The xeric (Greek: xeros, dry) moisture regime is the typical moisture regime in areas where winters are cool and moist and summers are warm and dry - i.e.
Plants in the Ustic Moisture Regime
A principle characteristic of ustic
Advantages
In many regions possessing thermic or mesic soil temperature regimes, there are relatively short warm seasons followed by a longer cold season, limiting the period during which grain can be harvested and re-planted. Consequently, these regions require rapid
Regions possessing an ustic soil moisture regime have a significantly large window for the harvesting of crops at the onset of the dry season. For example, Brazilian farmers in the
Gallery
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Aquic moisture regime
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Udic moisture regime
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Aridic moisture regime
See also
References
- ^ a b c d e Natural Resources Conservation Service. "Keys to Soil Taxonomy, United States Department of Agriculture, Natural Resources Conservation Service, Twelfth Edition, 2014".
- ^ a b c Natural Resources Conservation Service (2010). Keys to Soil Taxonomy (Eleventh ed.). United States Department of Agriculture. p. 28.
- ^ National Soil Survey Center. "Soil Survey Technical Note 9: Populating Taxonomic Moisture Class and Subclass in NASIS". United States Department of Agriculture. Retrieved 26 November 2014.
- ^ Grunwald, Sabine. "Mollisols". University of Florida - Soils & Water Science Department. Retrieved 17 October 2014.
- ^ "Soil Genesis and Development". Plant & Soil Sciences. Retrieved 20 October 2014.
- ^ Tim, Kettler. "Soil Genesis and Development, Lesson 6 - Global Soil Resources and Distribution". Plant & Soil Sciences eLibrary. National Science Publisher. Retrieved 17 October 2014.
- ^ Foth, Henry; Schafer, John W. Soil Geography and Land Use. New York: John Wiley & Sons.
- .
- ^ Soil Survey Staff (1981). Soil survey manual, Revised edition. Washington, D. C.: U. S. Govt. Printing Office.
- ^ .