Soils at some prehistoric agricultural sites in New Mexico were investigated to study agricultural adaptation in a semi‐arid mountainous region, evaluate soil productivity, and determine long‐term effects of agriculture on the physical environment. The sites, farmed during the Mimbres Classic period (about AD 1000 to 1150), occur within certain geomorphic settings, implying a strategy to optimize climatic and hydrologic conditions for runoff agriculture. The landscape was modified by terracing, which probably served to reduce runoff velocity, increase soil moisture, and thicken the naturally thin A horizon. Comparisons of prehistoric agricultural soils with nearby, similarly developed, uncultivated soils indicate significant differences in soil properties over eight centuries after farming ceased. Soil changes resulting from the prehistoric agriculture were mostly degradative, including accelerated erosion, compaction, and reduced concentrations of nutrients such as nitrogen and phosphorus. Despite soil degradation, study of maize growth in the soils suggests favourable productivity with fertilization and improved soil conservation. © 1990 Taylor and Francis Group, LLC.
