Order modifier

DI change

Rationale

Andisols

+4

Andic soil materials have high water retention properties

Alfisols, Ultisols

+3

Argillic horizon enhances water retention

Mollisols

+1

Large amounts of organic matter enhances water retention

Gelisols

-5

Frozen for much of the year, making soil water less accessible

Suborder modifier

DI change

Rationale

Arg

+3

Argillic horizon enhances water retention

Fluv

+2

Floodplain soils may have more incidents of extreme wetness/ponding

Calc, Gyps

+1

Calcic and Gypsic horizons facilitate water retention

Hum

+1

Large amounts of organic matter facilitate water retention

Dur

-2

Duripan (or ortstein) reduces rooting volume

Fol

-2

Thin to bedrock, Folists do not retain large amounts of water

Vitr

-2

Coarse textures reduce water retention

Sal

-3

Salty soil water is not always readily available to plants

Psamm

-6

Sandiness causes soils to drain freely and dry quickly

Great Group modifier

DI change

Rationale

Hist

+4

High organic matter contents point to additional wetness

Arg

+3

Argillic horizon enhances water retention

Hydr

+3

These soils have high water rentention capacities

Fluv

+2

Floodplain soils may have more incidents of extreme wetness/ponding

Melan

+2

Large amounts of organic matter facilitate water retention

Pale

+2

Strong development and thick Bt horizons facilitates water retention

Calci, Calc

+1

Calcic horizon facilitates water retention

Gyps

+1

Gypsic horizon facilitates water retention

Hum

+1

Large amounts of organic matter facilitate water retention

Somb

+1

Large amounts of organic matter facilitate water retention

Umbr

+1

Large amounts of organic matter facilitate water retention

Epi

-2

Perched water makes the upper profile wetter than it otherwise might be

Fol

-2

Drier than other Histels

Hal

-2

Salts reduce plant’s ability to utilize water

Natr, Na

-2

Sodium negatively influences soil water uptake by its influence on structure and water chemistry

Plinth

-2

Plinthite reduces rooting volume

Quartz

-2

Typically sandy, with little opportunity to retain water or neoform clay minerals, which retain water

Dur

-2

Duripan (or ortstein) reduces rooting volume

Vitr

-2

Coarse textures reduce water retention

Fragi, Fragloss

-3

Fragipan reduces deep percolation and commonly perches water

Petr

-3

Indurated horizon reduces rooting volume

Sal

-3

Salty soil water is not always readily available to plants

Anhy

-5

Anhydrous conditions typical of similar to cold, dry soils

Psamm

-6

Sandiness causes soils to drain freely and dry quickly

Subroup modifier

DI change

Rationale

Lamellic

+5

Lamellae enhance water holding capacity of otherwise xeric, sandy soils

Paleargidic

+5

Combination of Pale (+2) and Argidic (+3)

Andic, Aquandic, Udandic, Ustandic

+4

Andic soil properties typically impart high water retention capabilities

Histic, Thaptic-Histic

+4

High organic matter contents point to additional wetness

Calciargidic

+4

Combination of Calcic (+1) and Argic (+3)

Alfic, Argic, Aqualfic, Argiaquic, Argidic, Haploxeralfic, Ultic

+3

Bt horizon enhances water holding capacity

Albaquultic, Aquultic

+3

Implies strong Bt horizon and enhanced water holding capacity

Ruptic-Ultic, Ruptic-Alfic

+3

Bt horizon enhances water holding capacity

Hydric (in Histosols only)

+3

These soils contain a layer of water

Palexerollic

+3

Strong development and thick Bt horizons facilitates water retention

Ruptic-Histic

+3

High organic matter contents point to additional wetness

Cumulic

+2

Overthickened A horizon facilitates wtaer retention

Fluvaquentic, Fluventic, Torrifluventic, Udifluventic, Ustifluventic

+2

Floodplain soils may have more incidents of extreme wetness/ponding

Hydric (all but Histosols)

+2

These soils have high water rentention capacities

Vitrandic, Vitritorrandic, Vitrixerandic

+2

Coarse textures reduce water retention

Calcic, Calcidic, Gypsic, Haplocalcidic

+1

Calcic horizon facilitates water retention

Argiduridic

+1

Combination of Argic (+3) and Duric (-2)

Kandiudalfic, Kandiustalfic

+1

Bt horizon enhances wtaer retention, but low activity clays limit this effect

Natrixeralfic, Natrargidic

+1

Combination of Natr (-2) and Alfic (Argic) (+2)

Humic, Humaqueptic

+1

Large amounts of organic matter facilitate water retention

Mollic, Aquollic, Rendollic, Udollic, Ustollic, Xerollic, Haploxerollic

+1

Thicker A horizons facilitate water retention and infiltration

Pachic, Umbric

+1

High organic matter contents facilitate water retention

Ustalfic

+1

Bt horizon enhances water holding capacity

Fragic, Fragiaquic

-1

Fragipan reduces deep percolation and commonly perches water

Duric, Duridic

-2

Duripan (or ortstein) reduces rooting volume

Halic

-2

Salts reduce plant’s ability to utilize water

Natric

-2

Sodium negatively influences soil water uptake by its influence on structure and water chemistry

Plinthic, Plinthaquic

-2

Plinthite reduces rooting volume

Sodic

-2

Salts reduce the plant’s ability to utilize water

Vitric

-2

Coarse textures reduce water retention

Haploduridic

-2

Duripan reduces rooting volume

Salic, Salidic

-3

Salty soil water is not always readily available to plants

Terric

-3

Thin nature of histic epipedon suggests that the water table is not as high as in competing subgroups

Arenic

-4

Sandiness reduces water retention capacity and facilitates surface dryness

Ruptic-Lithic

-4

Half the value of Lithic (-8)

Petroferric

-4

Indurated horizon reduces rooting volume

Petrocalcic, Petrocalcidic, Petrogypsic

-5

Cemented subsurface pans reduce rooting volume

Grossarenic

-6

Thick, sandy surface horizons reduces water retention capacity and facilitates surface dryness

Psammentic, Torripsammentic

-6

Sandiness causes soils to drain freely and dry quickly

Lithic

-8

Shallow bedrock contact greatly reduces rooting volume