Soil Science
Chapter 17. Soil erosion and its control
(*: important concept)
Zueng-Sang Chen (陳尊賢)
Tel: 2369-8349, soilchen@ccms.ntu.edu.tw; http://Lab.ac.ntu.edu.tw/soilsc/
Printed on Dec 20, 2004
17.1 Significance of soil erosion and land degradation
 * Geological erosion by natural (Fig 17.4, p744) and accelerated erosion by people disturbed the soil.
17.2 On-site and Off-site effects of accelerated soil erosion
 * Three types of on-site damage: loss of organic matter and essential nutrients, and spread the plant
disease
 * Five types of off-site damage: Eutrophication, turbidity, windblown dust, human health hazard
materials, and loss the productivity.
17.3 Mechanics of water erosion
 * Three steps of process: detachment, transport and deposition (Fig 17.9, p751)
 * Three types of water erosion: sheet erosion, rill erosion, and gully erosion (Fig 17.10, p752).
17.4 Models to predict the extent of water-induced erosion
 * Universal soil loss equation (USLE) A=RKLSCP, related to rainfall (R), soil erodibility (S), slope
length (L), slope gradient (S), cover and management (C), and erosion-control practice (P).
 * Revised universal soil loss equation (RUSLE) (Table 17.3, p755)
 contour strip-cropping and grass waterways (Fig 17.15, p761)
 * calculation exercise of USLE (Box 17.1, p763)
17.6 Conservation tillage
 * Five types of conservation tillage system: No-tillage, ridge tillage, strip tillage, mulch tillage, and
reduced tillage (Table 17.9, p764)
 Comparison of different tillage systems: convention tillage (慣常耕犛), disk chisel (minimum tillage) and
no-tillage (Fig 17.20, p767)
17.7 vegetative barriers
 *the use of vegetative barrier to create the natural or living terrace (Fig 17.22, p769)
17.12 Predicting and controlling wind erosion
 E=ICKLV, related to soil erodibility factor (I), climate factor (C), soil-ridge-roughness (K), width of
field (L) and vegetative cover (V) (p783)
 Control of wind erosion: Shrub and trees make good windbreaks and add beauty (Fig 17.37, p786)
17.13 Land Capability Classification (LCC) as a guide to conservation
 * Eight classes of LCC related to intensity of land use (Fig 17.39, p788)
Discussion:
1. What are three important types of damages that result on the land whose soils are eroding?
2. Please explain the function of tree canopy, tree roots, and leaf litters in the forest ecosystem, which
provides the primary protection against the soil erosion.
3. Please compare the general soil loss (tons/ha/yr) of soil erosion between good soil conservation practice
(or slightly soil erosion) and serious soil erosion in Taiwan.