Agriculture Reference
In-Depth Information
Figure 7.14
Soil erosion by water on the lower slopes of the Côte d'Or, Burgundy. Photograph by the
author. See color insert.
of the slope (affecting the volume and velocity of water) and with surface cover
(affecting the resistance offered to water flow).
Land Management
. This complex factor includes the effect of land use and
land management practices. Bare soil is always more susceptible to erosion than
soil under vegetation. In the case of vineyards, susceptibility to erosion depends
on the time of year (winter versus summer), the distance between rows, and
whether the inter-rows are cultivated or under a cover crop. In the Côte d'Or of
Burgundy, clean cultivation of inter-rows on sloping land leads to considerable
soil erosion during summer thunderstorms (fig. 7.14). In the Willamette Valley
of Oregon, vignerons prefer to grow winter cover crops to protect the soil from
erosion. Generally, the difference in erosion on the same soil under different man-
agement practices is greater than the difference in erosion between different soils
under the same management.
7.5.2.3
Calculating Erosion Rates
The interaction between factors that determine the rainfall erosivity and soil erodi-
bility at a particular site is shown in figure 7.15. An explanation of the widely
used
Universal Soil Loss Equation
(
USLE
) is given in box 7.8.
7.5.3
Erosion by Wind
As with erosion by water, wind erosion depends on the potential of the wind to
erode (according to its energy) and the susceptibility of the soil. Wind erosion is
a serious problem only in low rainfall areas (
250-300 mm annually), because
only dry soil blows. However, a good cover of vegetation protects even dry soil.
