Agricultural land degradation by piping erosion in Chaco Plain, northwestern Argentina

Abstract

Soil piping has been pointed out as an important water erosion agent in a wide range of climatic regions. It is responsible for high soil losses in loess derived soils. The goal of this study is to evaluate the factors that are acting in the generation of piping processes and explain the mechanism of pipe collapse initiation. The study was carried out in loess derived soils located in a rural area of the Chaco Plain, between Tucuman and Santiago del Estero provinces, in northwestern Argentina. Pipe collapse types were described and soil loss estimation was performed. Factors influencing the process were studied under six different categories, i.e. physico-chemical and soil mechanical, soil mineralogical, microstructural, biological, and land use properties. In the study area, pipes took place in agricultural fields, principally in pastures, with slope gradients between 1% and 3%. Soil pipe collapse occurred in the area as a consequence of sudden wetting of the collapsible soils during summer storms. Pipe collapse forms vertical pipes or macropores that provide pathways for runoff directly into the soil pipe network. In addition, tension cracks adjacent to pipe collapses can provide pathways for preferential flow from the surface to the soil pipe network. With successive water infiltration the size of the pipes tends to increase and evolves to advanced stages of the process by internal erosion and eventually more pipe collapse. Blind gully formation is the final step of the piping process after the pipes roof collapse.