Base cation evidence for enhanced water infiltration in Ancestral Pueblo gravel mulch fields, Northern New Mexico, USA

In the Northern Rio Grande region of New Mexico, USA, Ancestral Pueblo villages experienced rapid demographic and economic growth in the late 14th and 15th centuries A.D. Recent research has proposed that this growth was underwritten by cotton production for exchange. Gravel mulch was an important component of cotton agriculture, but its function and soil legacies are not well understood. Since water management was likely a critical feature of gravel mulch, this study examines soil variables affected by changes to water supply. Gravel mulch analyzed in this study was found to have a substantial impact on the surface soil particle size distribution, but other aspects of soil quality were unaffected. The depth profiles of base cation ratios in mulched and unmodified locations suggest that gravel mulch continues to enhance water infiltration. Based on the timing of cotton development and inferred infiltration depths associated with gravel mulch soils, gravel mulch technology is well suited to the monsoonal precipitation regime of the region and the phenology of cotton.