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SOIL & WATER MANAGEMENT & CONSERVATION

The High Water-Holding Capacity of Petrocalcic Horizons

^a USDA-ARS, Jornada Experimental Range, Las Cruces, NM 88003-8003
^b Dep. of Plant and Environmental Sciences, New Mexico State Univ., Las Cruces, NM 88003-8003

^* Corresponding author (mduniway{at}nmsu.edu).

Petrocalcic soil horizons occur in most arid and semiarid ecosystems around the world, often within the plant rooting zone. Little is known, however, about the water-holding characteristic of soils indurated with CaCO₃. We conducted a replicated experiment to define the soil-water release curve (SWRC) for a range of petrocalcic horizon materials. Samples from both plugged and laminar zones of two Stage V petrocalcic horizons in southern New Mexico were characterized. Wetter soil-water potentials were measured using a pressure plate; more negative potentials (down to less than < –10 MPa) were measured using a chilled mirror water activity meter. Measured SWRC data were fitted to the van Genuchten equation. The SWRC methods used were found to be both reliable and repeatable. Plant-available water-holding capacity (AWHC) for desert species (with wilting point set at –4.0 MPa) ranged from 0.26 m³ m^–3 in plugged zones to 0.06 m³ m^–3 in some laminar zones in contrast to about 0.07 m³ m^–3 in the loamy sand parent material. Correlation analyses across morphologies of AWHC and soil properties resulted in significant statistical relationships only with bulk density and porosity. The AWHC and CaCO₃ content, however, were significantly negatively correlated within the laminar and positively correlated within the plugged petrocalcic horizon morphologies. Cementation by CaCO₃ dramatically alters the water-holding characteristics of soils and understanding these horizons is crucial to understand patterns of soil water in desert systems throughout the world.

Abbreviations: AWHC, available water-holding capacity • FC, field capacity • SWRC, soil-water release curve • WP, wilting point