Soil use in pre‐Hispanic and historical crop fields in the Guatacondo Ravine, northern Chile (2400 years BP): A geoarchaeological and paleobotanic approach

Abstract

In one of the most arid places on Earth, the Atacama Desert in northern Chile (18–21° S), pre‐Hispanic cultures developed different types of tillage and irrigation systems in the Guatacondo Ravine. Their agrarian production, based on a summer precipitation regime, enabled the formative villages of Ramaditas (2300–2600 years BP) and Guatacondo (2400–2800 years BP) to emerge, along with seasonal agriculture. Despite the insight gained into their agricultural technology, we know very little about how this type of soil management affected the soils' plant nutrient status. Thus, our main objective was to determine if the different tillage systems affected the soils' properties. We analyzed the soils and the pollen composition of different tillage systems and carried out direct radiocarbon dating (14C) of sediments. The soils' chemical properties (total nitrogen, phosphorus, and organic carbon contents) indicate greater nutrient retention in the square bed system, associated with a higher silt content and the use of organic fertilizers. Pollen analyses show the presence of crop, weed, and riparian species. In conclusion, the analysis of ancient soils gives us valuable information about the innovations and changes implemented in ancient times in the Guatacondo Ravine.

MODELING LONG-TERM HUMAN POPULATION DYNAMICS USING KERNEL DENSITY ANALYSIS OF 14C DATA IN THE ATACAMA DESERT (18º–21ºS)

“…The relatively lower intensity of human occupation in the Arica region and the region's later population growth could relate to horticultural social groups, who begin to continuously occupy the region thanks to the vegetal resources of the valley springs (Mu ñoz et al 2016). Our data suggest a more intense occupation of the Tarapacá region, related to earlier agricultural development, linked with irrigation and crop field features mainly in the lowlands (Segura et al 2021). There is a delay of approximately 2000 years in the change in estimated demographic trends in the Arica region, probably due to the difference in food production strategies, which involved an earlier and more intensive agricultural development in the Tarapacá region and a later and less intensive horticultural production in the Arica region.…”

Silvopastoralism and the shaping of forest patches in the Atacama Desert during the Formative Period (ca. 3000–1500 years BP)

“…3000-2000 BP (Berenguer, 2004;Briones et al, 2005;Núñez and Briones, 2022;Pimentel et al, 2011). Water supply favored human occupation of endorheic basins and riverbanks within the central depression or hyperarid core (Santoro et al, 2017;Segura et al, 2022). Legume forests of algarrobo are ubiquitous and abundant in these rising settlements.…”

‘White gold’ guano fertilizer drove agricultural intensification in the Atacama Desert from ad 1000

“…Recent studies of several hyperarid soils associated with certain archaeological sites where agricultural activity took place contain elevated concentrations of total organic C, N and PO4. These sites, located between 1000-3200 masl, date to 2000, 1000 and 400 years ago respectively, suggesting an anthropic influence in those periods 4,5 .…”