Assessment of erosion and deposition rates within an Austrian agricultural watershed by combining ¹³⁷Cs, ²¹⁰Pbex and conventional measurements

To control soil erosion and associated land degradation worldwide there is a need to assess the impact of major land use and the effectiveness of specific soil conservation technologies using various approaches. This study was conducted in an agricultural field at Mistelbach, Austria to assess the magnitude of deposition rates using Fallout RadioNuclides 'FRNs' (137Cs and 210Pbex) and the mid-term (13 years) erosion rates using conventional runoff plot measurements in a small agricultural watershed under conventional and conservation tillage/cropping practices. Long-term erosion measurements (1994-2006) from runoff plots located in the upper part of an agricultural field just up-slope from a deposition area reached 29.4 t ha- 1 yr- 1 from the conventional tilled plot, 4.2 t ha- 1 yr- 1 from the conservation tillage plot and 2.7 t ha- 1 yr- 1 from the direct seeding treatment. Soil losses were reduced significantly by a factor of 10 using no tillage, direct seeding treatment. Using 137Cs data that integrate the 1954-2007 period, the sedimentation rates down slope of the field containing the runoff plots were estimated to be 26.1 t- 1 ha- 1 yr- 1 using the 137Cs depth distribution profile and at 20.3 t- 1 ha- 1 yr- 1 using the Mass Balance Model 2 (MBM 2). The erosion rates under conventional tillage are in agreement with the sedimentation rates estimated down slope of the field by the 137Cs depth distribution profile and MBM 2. In the lowest part of the watershed sedimentation rates of up to 50.5 t- 1 ha- 1 yr- 1 were estimated through the 137Cs depth distribution profile. These rates were greater than the average erosion rates measured by the erosion plots because this area is more representative of sedimentation processes occurring in the study area due to its topographical position and the basin geomorphology. The 210Pb data obtained did not fulfil the requirements for the successful application of the methodology under the experimental conditions. This study demonstrates the complementarities of both methodologies (137Cs and runoff plots) to assessing erosion and sedimentation processes in an agricultural landscape. © 2009 Elsevier B.V. All rights reserved.