Alfredo Maestro Tejero's vineyards are located within the Ribera del Duero D.O., but Alfredo prefers not to participate in the D.O., so the wines are labeled Vino de la Tierra de Castillo y Le�n. His are completely natural wines, with no sulfur added in the vineyard or the winery. All vineyard treatments are natural, and many of them follow biodynamic practices.