ARS | Publication request: THE HIGH WATER-HOLDING CAPACITY OF PETROCALCIC HORIZONS

Submitted to: Soil Science Society of America Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: August 1, 2004
Publication Date: N/A

Technical Abstract: Petrocalcic soil horizons develop extensively in arid ecosystems around the world, often within the rooting zone of many desert plant species. In coarse-textured soils, this results in a dramatic change in moisture-holding capacity through the conversion of a horizon dominated by large pores to a fine-pore matrix. We conducted a replicated experiment to measure the characteristic moisture release curve for a range of petrocalcic horizon materials. Samples from both the plugged and laminar horizons from two stage V petrocalcic horizons in southern New Mexico were sampled. Tensions closer to zero were measured using a pressure plate; more negative tensions (down to -5Mpa) were measured using a chilled mirror water potential device (Decagon Devices WP4). Our method was repeatable and results were fitted using the van Genuchten equation. Plant available volumetric water-holding capacity for desert species (with permanent wilting point set at -4Mpa) ranged from 24% in plugged horizons to 3% in some laminar horizons in contrast to approximately 5.5% in a loamy sand. Cementation by calcium carbonate dramatically alters the water-holding characteristics of soils and understanding these horizons is crucial for understanding patterns of soil water in desert systems.