Soils in ancient irrigated agricultural terraces in the Atacama Desert, Chile

Abstract

The Atacama Desert is among the driest places on Earth, yet ancient agricultural systems are present in the region. Here, we present a study of terraced agricultural soils in the high‐altitude eastern margin of the Atacama Desert in northern Chile, mainly dating to the Late Intermediate Period (ca. 950–1400 AD) and Inka period (ca. 1400–1536 AD). Terraced fields were compartmentalized to distribute limited irrigation water originating mainly from springs. Natural soils used for agriculture are mostly Aridisols developed on Pleistocene alluvial fan terraces and hillslopes underlain by volcanic bedrock. One research objective is to evaluate long‐term soil change from agriculture. In this hyperarid climate, agriculture is only possible with irrigation, so natural soils on the same geomorphic surface adjacent to irrigated soils provide baseline data for assessing anthropogenic soil change. Data from soil profiles and surface transects indicate intentional soil change through terracing, removal of soil rock fragments, and probable fertilization. Agricultural soils have anthropogenic horizons ranging from 16 to 54 cm thick. Most agricultural soils have higher phosphorus levels, suggesting enrichment from fertilization. Changes in soil organic carbon and nitrogen are also evident. Unintentional anthropogenic soil change resulted from CaCO3 input through irrigation with calcareous spring water. Initial studies suggest that agriculture here was sustainable in the sense of conserving soils, and maintaining and possibly improving soil productivity over centuries.

An integrative approach to ancient agricultural terraces and forms of dependency: the case of Cutamalla in the prehispanic Andes

“…With the exception of a few more densely populated highland zones such as the Cusco region, however, only a fraction of ancient farming terraces are still in use nowadays and they are often in rather poor condition, modified, or even demolished because of modern and mechanized methods of agriculture. In contrast, the soil fertility of ancient terraced fields can remain high (Nanavati et al, 2016;Sandor et al, 2022), even if they have been abandoned or poorly maintained (for research with different findings, see Goodman-Elgar, 2008). In general, whether the properties of agricultural soils improve or degrade over time is related to a combination of environmental, agricultural, and social factors (Sandor and Homburg, 2017).…”

Building resilience from risk: Interactions across ENSO, local environment, and farming systems on the desert north coast of Peru (1100BC–AD1460)

“…Today, soils in Pampa de Mocan are classified as regosols, or unconsolidated materials, originating from relatively recent erosional or alluvial formations, and lacking horizons – undeveloped and low in organic matter (see Watson, 1979: 208; ONERN, 1973). However, studies show that these soil conditions can be partly mitigated via the deposition of fine sediments through the application of irrigation water (Sandor et al, 2022; Strawhacker, 2013). For example, natural quebrada soils in the Pampa de Mocan are gravelly and highly permeable, allowing for good drainage.…”

“…For example, natural quebrada soils in the Pampa de Mocan are gravelly and highly permeable, allowing for good drainage. Repeated application of silt suspended in irrigation water would increase the silt and clay content of these soils, resulting in increased water retention capacity and chemical reactivity, which can enhance fertility (see Hesse and Baade, 2009; Sandor et al, 2022).…”

The Anthropocene: Comparing Its Meaning in Geology (Chronostratigraphy) with Conceptual Approaches Arising in Other Disciplines

“…The soil scientists Certini and Scalenghe (2011) proposed that anthropogenic soils as old as 2000 BP mark the beginning of the Anthropocene, for human‐altered soils mark a substantial global impact of humans on the total environment, and by 2000 BP civilization's effects on soils were extensive. From local to regional scales, soil scientists have documented the long history of human–soil relations in Africa, Asia, Europe, and the Americas (McNeill & Winiwarter, 2004; Sandor, 2006). Amundson and Jenny (1991) evaluated the variety of ways that soils have been altered by Pacific island colonizers, indigenous peoples of North America, Midwestern US farmers, and nineteenth and twentieth century city‐park managers.…”