『Abstract
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 Radio Nuclides ‘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 ha-1 yr-1
using the 137Cs depth distribution profile and at 20.3
t 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 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 fulfill 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.
Keywords: Soil erosion; 137Cs; 210Pb; Erosion
plots; Sedimentation rates; Erosion rates』
1. Introduction
2. Materials and methods
2.1. Study area
2.2. Runoff and erosion measurements using conventional erosion
plots
2.3. Soil sampling design in the reference site
2.4. Laboratory analyses
2.4.1. Samples pre-treatment, gamma spectrometry measurements
2.4.2. Physiochemical analysis of the reference site soil
2.5. Estimates of the 137Cs areal activity and conversion
into soil redistribution
3. Results and discussion
3.1. Erosion rates obtained with the conventional erosion
plots
3.2. Physiochemical characterization of the reference site and
evaluation of the 137Cs baseline level
3.3. 210Pb baseline level and test of the 210Pb
methodology
3.4. Assessment of soil deposition rates using 137Cs
data
4. Conclusions
Acknowledgements
References