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KAB.Petraquepts

Key to Great Groups 

KAB. Other Aquepts that have, within 100 cm of the mineral soil surface, one or more horizons in which plinthite or a cemented or indurated diagnostic horizon either forms a continuous phase or constitutes one-half or more of the volume. Petraquepts, p. 509 

KAB. These are the Aquepts that have one or more horizons, within 100 cm of the mineral soil surface, in which plinthite or a cemented or indurated diagnostic horizon either forms a continuous phase or constitutes one-half or more of the volume. A layer of plinthite and the placic horizon are the only horizons known to occur in the Petraquepts in the United States. A Typic subgroup is provided for Petraquepts with a duripan or petrocalcic horizon. Petraquepts are soils in which the ground water table fluctuates considerably during the year, between a level at or near the soil surface during the rainy season and a much lower level during less wet seasons. A histic or umbric epipedon and a cambic horizon may be present. In some of the soils, the placic horizon is so close to the soil surface that there is no cambic horizon above it. Petraquepts are in areas of very high rainfall. The vegetation may be a rain forest, Sphagnum, or other waterloving plants. The temperature regime is frigid to isohyperthermic. Slopes generally are such that water does not pond on the surface, but high rainfall keeps some of the soils continuously wet. Petraquepts are rare in the world. 

Definition 

1. Petraquepts are the Aquepts that have, within 100 cm of the mineral soil surface, one or more horizons in which plinthite or a cemented or indurated diagnostic horizon either forms a continuous phase or constitutes one-half or more of the volume; and

2. Do not have a sulfuric horizon that has its upper boundary within 50 cm of the mineral soil surface. 

Key to Subgroups 

KABA. Petraquepts that have both:

1. A histic epipedon; and

2. A placic horizon. Histic Placic Petraquepts 

KABB. Other Petraquepts that have a placic horizon. Placic Petraquepts 

KABC. Other Petraquepts that have one or more horizons within 125 cm of the mineral soil surface in which plinthite either forms a continuous phase or constitutes one-half or more of the volume. Plinthic Petraquepts 

KABD. Other Petraquepts. Typic Petraquepts 

Definition of Typic Petraquepts 

Typic Petraquepts are the Petraquepts that:

1. Do not have a placic horizon; and

2. Do not have one or more horizons within 125 cm of the mineral soil surface in which plinthite either forms a continuous phase or constitutes one-half or more of the volume.

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