Use of 7Be to document soil erosion associated with a short period of extreme rainfall

摘要

Intensification and expansion of agricultural production since the 1970s have increased soil erosion problems in south-centraludChile. Quantitative information on soil loss is needed for erosion risk assessment and to establish the effectiveness of improved landudmanagement practices. Since information from traditional sources, such as erosion plots, is limited, attention has been directed toudthe use of environmental radionuclides for documenting erosion rates. Cs-137 has been successfully utilised for this purpose, butudonly provides information on medium-term erosion rates. There is also a need to document event-related soil erosion. This paperudoutlines the basis for using 7Be measurements to document short-term erosion and reports its successful use for quantifying theuderosion that occurred within an arable field, as a result of a period of heavy rainfall (400 mm in 27 days) occurring in Mayud2005. The study field had been under a no-till, no-burning system for 18 years, but immediately prior to the period of heavy rainfalludthe harvest residues were burnt. The erosion recorded therefore reflected both the extreme nature of the rainfall and the effects of theudburning in increasing surface runoff and erosion. The sampled area corresponded to that used previously by the authors to documentudthe medium-term erosion rates associated with both conventional tillage and the subsequent switch to a no-till system. Comparisonsudbetween the erosion documented for the period of heavy rainfall in 2005 with these medium-term erosion rates permits someudtentative conclusions regarding the importance of extreme events and the impact of burning in increasing the erosion associatedudwith the no-till system.