Anthrosols on terraced soilscapes of the Atacama Desert: Physical and chemical properties of millennial-scale cultivation legacy

ABSTRACT Integrating ancestral agricultural techniques into modern practices is essential to developing sustainable, resilient food systems in environments constrained by limited natural resources. This study investigated the Anthrosols of the Atacama Desert, analyzing how traditional populations managed and transformed local soils to enable sustainable agriculture under extreme arid conditions. To this end, samples of cultivated and natural soils were collected in six villages in the province of El Loa, characterizing their granulometry, the content of organic matter, macro and micronutrients, electrical conductivity and soluble anions, besides the mineralogy of the clay fraction by X-ray diffractometry. Statistical analyses (Kruskal-Wallis and Kendall tests) were used to evaluate differences and correlations between the parameters studied. Based on the study of cultivated soils, the results indicate that these Anthrosols underwent three distinct processes of anthrosolization: (1) the construction of terraces with selected materials, involving the removal of larger gravels and the concentration of finer particles, providing more favorable agricultural conditions; (2) irrigation management with Andean meltwater, enriching soils with Na, Ca, and Mg, while maintaining pH range without inducing salinization; and (3) the addition of animal manure, significantly increasing the organic matter and nitrogen contents compared to adjacent reference desert soils. Particle size analysis revealed a higher content of fine particles in cultivated soils (CS) compared to non-cultivated soils (NCS), resulting in greater water retention and improved soil structure. Chemical analysis indicated higher pH, cation exchange capacity, and base saturation values in CS, while phosphorus levels remained similar between CS and NCS, suggesting a high regional natural background of volcanic materials. The mineralogy of the clay fraction evidenced the presence of 2:1 (illite, smectite) and 1:1 (kaolinite) minerals, in addition to the formation of secondary carbonates in some CS, probably associated with irrigation practices. These Anthrosols, as ancestrally built and managed, represent valuable archaeological records of agricultural knowledge and have the potential to support long-term, sustainable cultivation strategies in arid environments subject to water scarcity and adverse climate conditions.