Drylands critical zone project: Soil sensor data in an irrigated pecan orchard of western Texas

Abstract
In natural drylands, the formation of pedogenic carbonate (secondary calcite, CaCO3) is critical in impacting the soil properties hydrologically and biogeochemically, and modifying the global carbon cycle over geological time. When dryland ecosystems are converted to managed agricultural sites, irrigation water supplies HCO3- and Ca2+, accelerating the rates of CaCO3 formation and releasing abiotic CO2. We investigated the abiotic and biotic processes that have produced soil CO2 in dryland soils at an irrigated pecan orchard in Tornillo, Texas. Two sites within the pecan orchard, Pecan_Coarse, and Pecan_Fine, have contrasting soil textures resulting in different soil salinity, pedogenic carbonate accumulation rates, and tree sizes. A range of methods was employed including soil CO2, soil O2, and soil moisture sensors at two different soil depths (30 cm and 60 cm below ground surface). The overall objective of this study is to quantify the release of abiotic CO2 during the precipitation of irrigation-induced calcite, as a function of spatial variability due to soil texture, and as a function of growing season and irrigation events at a high temporal scale.