TERROIR OF THE TEXAS HIGH PLAINS

The Texas High Plains is a major wine grape production region of Texas and has been officially recognized as an American Viticultural Area (AVA) since 1993. The AVA is located (centroid approximately 33.5N, 102.1W) south of the Texas Panhandle and lies within the High Plains subregion that is part of the southernmost extension of the Great Plains province. The distinctive characteristics of the Texas High Plains are derived from its unique terroir - a semi-arid climate with hot summers and mild winters, the high-elevation level plain, sedimentary and eolian geology, and very deep, well-drained soils found nowhere else in the State. Vineyards are planted primarily on three similar soil series widely found in the region. These are very deep, well drained, moderately permeable soils derived from sandy (Patricia and Brownfield series) or loamy (Amarillo series) eolian sediments from the Blackwater Draw Formation of Pleistocene age. These soils are well-suited for grape production with low to moderate fertility and good drainage, yet adequate water-holding capacity. Climatic conditions are also conducive to high quality grape production; relatively low annual precipitation of 43.7-52.6 cm (17-21 in) enables grapevine vigor management through irrigation practices. This is an important tool for optimizing canopy microclimate for fruit quality. Low rainfall and low relative humidity also provide an environment not conducive to most fungal diseases of grapes. The region receives an average of 2341 ^oC growing degree-days (April-October, 10 ^oC base). Although the region is considered a hot climate for grape production based on degree-days, temperatures become favorably moderate at night during the fruit ripening period owing to the high elevation and low relative humidity. High solar radiation contributes to vine fruitfulness and very good color development in red wine grapes.