B. Barthes et al., Relationship between soil erodibility and topsoil aggregate stability or carbon content in a cultivated Mediterranean highland (Aveyron, France), COMM SOIL S, 30(13-14), 1999, pp. 1929-1938
In the Rougiers de Camares area (in the south of France), hillslopes are ve
ry susceptible to water erosion. This is the result of physical features (s
teep slopes, soft bedrocks, thin soils), climatic aggressiveness (frost, st
orms), as well as farming systems (intensive tillage, short crop cycles, la
nd consolidation). The objective of this work was to study the relationship
s between soil erodibility, macroaggregate stability, and carbon content of
surface samples (0-10 cm), in a Rougiers Entisol (Lithic Udorthent) under
various management practices (flat or raised moldboard ploughing, superfici
al tillage, direct drilling, with inputs in the form of mineral fertilizers
or sheep manure). The soil erodibility was assessed by field rainfall simu
lation (60 mm h(-1)) on manually retilled bare dry soil; water-stable macro
aggregation (>0.2 mm) was assessed by wet-sieving, after immersion in water
. Runoff, turbidity and soil losses were linked to water-stable macroaggreg
ation and carbon content in the 0-10 cm layer. During the first 30 minutes
of rainfall, runoff and soil losses were closely correlated with topsoil in
itial water-stable macroaggregation, but not with topsoil carbon content (a
lthough there was a correlation between water-stable macroaggregation and c
arbon content). At the end of the rain (runoff steady state), turbidity and
soil losses were closely correlated with topsoil carbon content, and to a
lesser extent, with water-stable macroaggregation. Water-stable macroaggreg
ation (which prevents crusting) and carbon content (which has an effect upo
n liquidity limit, among others) were thus important determining factors of
erodibility for the studied soil. The influence of management practices on
soil erodibility was therefore dependent upon their effects on these facto
rs.