Editing USDA soil taxonomy (section)

== Soil moisture regimes ==
[[File:United States Soil Moisture Regimes.jpg|thumb|upright=1.6|United States distribution of soil moisture regimes]]
[[File:Global Distribution of Soil Moisture Regimes.jpg|thumb|upright=1.6|Global distribution of soil moisture regimes]]

The soil moisture regime, often reflective of climatic factors, is a major determinant of the productivity of terrestrial ecosystems, including agricultural systems. The soil moisture regimes are defined based on the levels of the groundwater table and the amounts of soil water available to plants during a given year in a particular region. Several moisture regime classes are used to characterize soils. These categories are terminology modifiers at the soil suborder level of characterization.

{| class="wikitable"  style="margin:auto;"
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! scope="col" style="width:100px;" rowspan="1.5"| Soil Moisture Regime
! scope="col" style="width:850px;" colspan="1.5"| Major Characteristics
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| Aquic || Soil is saturated with water and virtually free of gaseous oxygen for sufficient periods of time, such that there is evidence of poor aeration (gleying and mottling); common in wetlands.
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| [[Udic moisture regime|Udic]] || Soil moisture is sufficiently high year-round in most years to meet plant requirement; common in humid regions.
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| [[Ustic]] || Soil moisture is intermediate between Udic and Aridic regimes; generally, plant-available moisture during the growing season, but severe periods of drought may occur; common in semi-arid regions.
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| Aridic || Soil is dry for at least half of the growing season and moist for less than 90 consecutive days; common in arid (desert-like) regions.
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| Xeric || Soil moisture regime is found in Mediterranean-type climates, with cool, moist winters and warm, dry summers. Like the Ustic Regime, it is characterized as having long periods of drought in the summer.
|-
|}