Distribution and Formation of Two Calcareous soils on the southern high plains of Texas

A distinct taxonomical difference was recognized within the Estacado mapping unit on the Southern High Plains (SHP), in MLRA (Major Land Resource Area) 77C. The difference recognized prompted an investigation on whether or not a new soil series needed to be added to the legend of many counties on the SHP. The potential new soil, the Bovina series, will be identified and separated from the Estacado soil. The Estacado series is classified as Fine-loamy, mixed, superactive, thermic Aridic Paleustolls, and the proposed Bovina series is classified as Fine-loamy, mixed, superactive, thermic Calcidic Paleustolls. The primary characteristic of interest is the depth to calcic horizon (horizon with 15 percent or more secondary carbonate). The concept of the Bovina series is the same as the Estacado soil except the calcic horizon is shallower than 60 cm, while the Estacado series has a calcic horizon deeper than 60 cm. Taxonomically, it has also been observed that the particle size control section is also a factor, because many soils mapped Fine-loamy border fine and fine-silty. Progressing from southwest to northeast across the SHP, the particle size control section become fine and fine-silty rather than fine-loamy, due to the general fining in this direction.
The interpretations between these two soils differ greatly. The Bovina soil would be considered HEL (Highly Erodible Land), because of the shallow calcic horizon. This means it would be considered first for government conservation programs such as CRP (Conservation Reserve Program) and EQUIP (Environmental Quality Incentive Program). Landscape relationships are fundamental to understand soil formation, distribution and occurrence. A study was conducted on two calcareous soils on the SHP of Texas to better understand and predict their occurrence and variability across the landscape. Physical, chemical, mineralogical, morphological and characteristics were used as tools in addition to GIS (Geographic Information Systems) mapping. GIS was used to examine landscape relationships, such as depth to the calcic horizon. Sand/silt ratios, clay mineralogy, and carbonate percentages were used to study the lithology.