Abstract

Purpose Nadi soils (Aquands) are derived from volcanic ashes and have a limited effective depth that restricts the movement of water throughout their profiles. Drainage systems are therefore essential for the productive use of these soils, though these may induce soil shrinkage/subsidence. The aim of this work was to evaluate the shrinkage potential and curves of Aquands along a longitudinal climatic gradient in southern Chile (from 38 DEG; to 42 DEG; S). Methods Undisturbed and disturbed soil samples of five soil series under pasture were collected in metallic cylinders and plastic bags, respectively, from two soil depths (0-20 and 20-40 cm). A peat soil was also used as a reference of a soil with a high shrinkage capacity that has not historically suffered water stress. Shrinkage curves were measured and their phases were determined. Soil shrinkage parameters, bulk density, air capacity, soil organic carbon (SOC), and extractable aluminum (Al-a) were also determined. Results From north to south, as the SOC increased, the shrinkage potential of the soils increased as well. Shrinkage curves showed clear structural and wide proportional shrinkage, with an absence of zero shrinkage. The hydraulic stress caused by drainage affected the pore shrinkage capacity and could lead to high subsidence and, in turn, a decrease in soil depth. Conclusions Aquands showed a very high shrinkage capacity (COLE 0.09), which was positively related to their OC content and negatively related to the initial bulk density of the soil. After drying events (- 500 hPa), Aquands reached a volume decrease of up to 25%, reflecting a low resilience capacity that, in turn, affects the soil physical properties, i.e., structure, subsidence, and soil depth. The observed increase in shrinkage processes in the Nadi soil transect may be due to the accumulated OC content created by the extremely waterlogged conditions associated with the edaphoclimatic conditions under which these soils were developed.