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KEC.Fragixerepts

Key to Great Groups 

KEC. Other Xerepts that have a fragipan that has its upper boundary within 100 cm of the mineral soil surface. Fragixerepts, p. 549 

KEC. These are the Xerepts that have a fragipan within 100 cm of the mineral soil surface. Commonly, these soils have a brownish cambic horizon that is underlain by a fragipan at a depth of about 70 cm. Most Fragixerepts have perched water above the pan in winter, and few roots penetrate the pan. Consequently, plants tend to have shallow root systems. Many Fragixerepts formed in late-Pleistocene deposits. They have mostly gentle or moderate slopes, but some are steep. Most of these soils are loamy and have been leached of any free carbonates. The Fragixerepts in the United States are mostly in the States of Idaho and Oregon. They are of small extent. 

Definition 

Fragixerepts are the Xerepts that:

1. Have a fragipan within 100 cm of the mineral soil surface;

2. Do not have a duripan within 100 cm of the mineral soil surface; and

3. Do not have both:

                a. A calcic horizon with its upper boundary within 100 cm of the mineral soil surface or a petrocalcic horizon with its upper boundary within 150 cm of the mineral soil surface; and

                b. Calcareous materials in all parts above the calcic or petrocalcic horizon, after the soil between the mineral soil surface and a depth of 18 cm has been mixed. 

Key to Subgroups 

KECA. Fragixerepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, a fine-earth fraction with both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa water retention, and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling more than 1.0. Andic Fragixerepts 

KECB. Other Fragixerepts that have, throughout one or more horizons with a total thickness of 18 cm or more within 75 cm of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser than 2.0 mm, of which more than 66 percent is cinders, pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and

                a. In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and

                b. [(Al plus 1/2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more. Vitrandic Fragixerepts 

KECC. Other Fragixerepts that have, in one or more horizons within 30 cm of the mineral soil surface, distinct or prominent redox concentrations and also aquic conditions for some time in normal years (or artificial drainage). Aquic Fragixerepts 

KECD. Other Fragixerepts that have an umbric or mollic epipedon. Humic Fragixerepts 

KECE. Other Fragixerepts. Typic Fragixerepts 

Definition of Typic Fragixerepts 

Typic Fragixerepts are the Fragixerepts that:

1. Do not have, throughout a cumulative thickness of 18 cm or more and within a depth of 75 cm, one or more of the following:

                a. A bulk density, in the fraction less than 2.0 mm in size, of 1.0 g/cm3 or less, measured at 33 kPa water retention, and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

                b. Fragments coarser than 2.0 mm constituting more than 35 percent of the whole soil and cinders, pumice, and pumicelike fragments making up more than 66 percent of these fragments; or

                c. A fine-earth fraction containing 30 percent or more particles 0.02 to 2.0 mm in diameter; and

                                (1) In the 0.02 to 2.0 mm fraction, 5 percent or more volcanic glass; and

                                (2) [(Al plus 1/2 Fe, percent extracted by ammonium oxalate) times 60] plus the volcanic glass (percent) is equal to 30 or more;

2. Do not have, in any horizon within 30 cm of the mineral soil surface, distinct or prominent redox concentrations and also aquic conditions; and

3. Do not have an umbric or mollic epipedon.

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