1867-68 college of soil physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 college of soil...
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1867-68
College of Soil Physics
Donald Gabriels
22 October - 9 November, 2007
Dept. Soil ManagementGhent University
Belgium
Factors affecting the water erosion process.
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Donald GabrielsResearch group
Soil erosion and Soil conservationGhent University, Belgium
COLLEGE ON SOIL PHYSICS
Water erosion: factorsWATER EROSION: FACTORS
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Erosion by water – How?
Ploegzool
Ponding
Infiltration
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Sheet erosion (splash erosion and overland flow)
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Transport due to wind-driven rain
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Transport due to wind-driven rain
u* and KEz or Mz
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Sheet erosion
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Interrill erosion
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Rill erosion
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Gully erosion
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Natural factors influencing soil erosion (by water)– rainfall erosivity
• intensity– soil erodibility
• particle size (silt and fine sand)• clay content • organic matter content• (embedded) stones
– topography • slope steepness
– vegetation• surface cover• canopy cover• roots
reduce rainfall erosivity
reduce soil erodibility
Erosion by water is a natural process ...
aggregate stability
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Human factors– harvest of vegetation
• loss of soil cover– soil tillage
• decrease in organic matter and biological activity
• compaction of subsurface layers– surface sealing (e.g. roads, pavement)
• increase of overland flow
…but can be influenced by human practices
Erosion > soil loss tolerance
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Soil loss tolerance value:depends on the on and off site effects of soil erosion
• on site: depth of fertile soil layer→ values proposed by the Soil Conservation
Service (Logan, 1982)
• off site: – water quality (e.g. eutrophication risk)– silting up of reservoirs and ditches– risk of flooding
soil depth (cm) soil loss tolerance (t/ha yr)
< 25 till solid rock 2.2< 25 till sand 4.5
25 to 50 till solid rock 4.525 to 50 till sand 6.7
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What are the consequences?• On site
– decrease of soil quality– filling up of gullies– loss of yield, nutrients, pesticides
• Off site– mudflows– silting up of reservoirs– deterioration of water quality
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Loss of soil qualityLoss of soil quality
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Formation of gullies
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Loss of yield
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Mudflows
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Silting up reservoirs
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Deterioration of water quality (eutrophication)
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How can we measure it?• Laboratory:
• soil pans• rainfall simulations• flume experiments
• Field• erosion plots• rainfall simulations• flume experiments
• Watershed• deposition in reservoirs• sediment discharge at the outlet
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• Laboratory rainfall simulation
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• Field rainfall simulation
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• Field plot (flume with pressure transducer + collector drum)
Field plot 1
Flume
Pressure sensor Runoff Collector
Field plot 1Field plot 1
Flume
Pressure sensor Runoff CollectorRunoff
Collector
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• Watershed(ultrasonic sensor to determine the water level)
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• Watershed(sampling device)
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• Watershed(turbidity sensor)
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Universal Soil Loss Equation – USLE (1978)
Revised USLE – RUSLE (1997)
A = soil loss (sediment yield) per unit area(Mg ha-1 year-1)
R = rainfall-runoff erosivity factor (MJ mm ha-1 h-1 year-1)
K = soil erodibility factor(Mg ha h-1 MJ-1 mm-1)
LS = slope-length factorC = cover-management factorP = supporting practices factor
A = R x K x LS x C x P
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R – Rainfall-runoff erosivity factor
• Potential of rain to detach and transport sediment
• Rainfall is characterised by
– amount of rainfall (precipitation)– duration of rain storm– intensity of rainfall– momentum or kinetic energy of raindrops
• Wischmeier and Smith (1958): R = E I30
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Kinetic energy E
• KE of single raindrop
Ei = ½ mi vi2
• KE of rainstorm
E = ∑ Ei
impossible → group raindrops into classes of equal size (and hence m and v)
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• Determine raindrop-size distribution
– stain technique: paper + appropriate dye
– photographic methods
– immersion method: heavy grade oil
– flour pellet: flour on plate
– impact assessment: tension balance, acoustic device,
pressure transducer (distrometer)
– optical spectro-pluviometer: laser technique
Drop-size distribution depends largely on intensity (!!!),
origin of raindrop, type of cloud – max. 7 mm
For each drop size (class): calculate m = 1/6 π d3 (ρw-ρa)
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determination of v: from Laws (1949)
→ m + v → E
very labor intensive
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•“Direct” measurement of KE (needs calibration)
– Ellison splash cups (1947)
– Sensit KE meter: piezo-electrical crystals
still too labor intensive for practical purposes
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•Indirectly from intensity: Renard et al. (1991)
KE of pluviophase j
Epj = 0.29 [1 – 0.72 exp(-0.05 Ij)] ∆Pj
KE of rainstorm
Epj = KE of pluviophase j (MJ ha-1)Ij = rainfall intensity of pluviophase j (mm h-1)∆Pj = depth of rainfall of pluviophase j (mm)
E = ∑ Epj
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R – Rainfall-runoff erosivity factor
• Potential of rain to detach and transport sediment
• Rainfall is characterised by
– amount of rainfall (precipitation)– duration of rain storm– intensity of rainfall– momentum or kinetic energy of raindrops
• Wischmeier and Smith (1958): R = E I30
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I30 = maximum rainfall intensity in a 30 minute period within the rainstorm (mm h-1)
• pluviograph
• tipping bucket pluviometer (rain gauge)
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0
2
4
6
8
10
12
7:26
:24
PM
7:40
:48
PM
7:55
:12
PM
8:09
:36
PM
8:24
:00
PM
8:38
:24
PM
8:52
:48
PM
9:07
:12
PM
9:21
:36
PM
9:36
:00
PM
9:50
:24
PM
10:0
4:48
PM
10:1
9:12
PM
10:3
3:36
PM
10:4
8:00
PM
11:0
2:24
PM
11:1
6:48
PM
11:3
1:12
PM
time
inte
nsity
(mm
/h)
I30 = 8.74 mm h-1
30 min
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R – Rainfall-runoff erosivity factor
• Potential of rain to detach and transport sediment
• Rainfall is characterised by
– amount of rainfall (precipitation)– duration of rain storm– intensity of rainfall– momentum or kinetic energy of raindrops
• Wischmeier and Smith (1958): R = E I30
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Experimental models: USLE
• Calculation of mean annual rainfall erosivitymethod 1: R = 0.5 P
with P = mean annual rainfallremark: outcome is in american units
→ R’ = 17.3 x R (Mg mm ha-1 h-1)
method 2 (for KE > 25): E = 9.28 P – 8.838R = EI30/100
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Experimental models: USLE• Exercise: Calculate R if the mean annual
precipitation P equals 2695 mm.
method 1: R = 0.5 x P
method 2 (for KE > 25): Use I30 = 75 mm h-1
E = 9.28 x P – 8.838
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Experimental models: USLE• Exercise: Calculate R if the mean annual
precipitation P equals 2695 mm.
method 1: R = 0.5 x 2695= 1347.5= 1347.5 x 17.3= 23 311.8
method 2 (for KE > 25): Use I30 = 75 mm h-1
E = 9.28 x 2695 – 8.838= 16 171 J m-2 = 16 171.6 Mg ha-1
R = (16 171.6 x 75)/100= 12 128.7
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0
4
8
12
rege
nero
sivi
teit
%R
[%]
jan febr ma apr mei jun jul aug sept okt nov dec40
60
80
100
gem
idde
lde
maa
ndel
ijkse
nee
rsla
g Pm
[mm
]
%R
Pm
Monthly rainfall Pm and rainfall erosivity R at Ukkel (Belgium, period 1967- 1993)
equal distribution
large variations
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problem: many weather stations do not have pluviograph or tipping bucket pluviometer
R = 11.55 exp(0.0254 MFI)
e.g. Belgium (Michiels and Gabriels, 1993)
MFI = Modified Fournier Index
∑=
==
12
1
2i
i
iPp
pi = mean monthly rainfall in month iP = mean annual rainfall
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e.g. Belgium (Michiels and Gabriels, 1993)
R = 11.54 exp(0.00215 P)
e.g. Ethiopia (Hurni, 1985)
R = -8.12 + 0.562 P
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K – Soil erodibility factor
• Vulnerability or susceptibility of soil against erosion
• Erodibility depends on
– soil texture (silt + very fine sand fraction)– organic matter content– soil structure– permeability – hydraulic conductivity
– initial soil-water content
• K = soil loss (sediment yield) per unit of R on a standard plot (22.1 m long; 9% slope), continuous fallow for 2 years, tilled up and down the hill
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⎯→ K = A/R LS = C = P = 1
A = R x K x LS x C x P
A
R
**
**
*
K
• from erosion plots
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• in practice (RUSLE):
K = 0.1317 [2.1 10-6 (12 – OM) M1.14 + 0.0325 (S – 2) + 0.025 (P – 3)]
M = (% of 2-100 µm fraction) x (100 - % of < 2 µm fraction)OM = % of organic matterS = structural classP = permeability class
valid for % of 2-50 µm fraction < 70%
(1) via “nomogram”
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aggreg. size< 1 mm1-2 mm2-10 mm
-
Ks (cm h-1)< 0.125
0.125-0.50.5-22-6.25
6.25-12.5>12.5
![Page 49: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/49.jpg)
Experimental models: USLE
• Exercise: 70 % silt + fine sand, 20 % coarse sand, OC = 1 %, medium granular structure, slow to moderate permeability
K-Value = 0.62
![Page 50: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/50.jpg)
(2) via mean weighted diameter Dg (Declercq and Poesen, 1992)
K = 0.0035 + 0.0388 exp[-0.5((log(Dg)+1.519)/0.7584)2
Dg = exp[0.01 ∑(fi ln(mi))]
Dg = mean weighted diameter (mm)fi = fraction of particles belong to diameter class i (mass%)mi = mean diameter of diameter class i (mm)
![Page 51: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/51.jpg)
USLE: considers K is constant over season
RUSLE: considers seasonal variation (structure, antecedent soil-water content, frost, …)
by weighing instantaneous estimate of K in proportion to EI (the percent of annual R) for 15-day intervals
![Page 52: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/52.jpg)
• soil structure– organic matter– soil conditioners⇒ increase of aggregate stability
against raindrop impact ⇒ more infiltration
– breaking of compacted ploughsole– controlled traffic
![Page 53: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/53.jpg)
• aggregate stability at different organic carbon contents (clay content = 19 %)
0.000.100.200.300.400.500.600.700.80
1.1 1.75 1.9
organische koostof (%)
aggr
egaa
tsta
bilit
eit
organic carbon content (%)
aggr
egat
e st
abili
ty
![Page 54: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/54.jpg)
0
10
20
30
40
50
0 5 10 15 20 25
tijd (min)
infil
tratie
(mm
) .
niet verslemptverslempt
• infiltration with and without soil sealing (resp. low and high aggregate stability)
not sealed
sealed
time (min)
infil
trat
ion
(mm
)
![Page 55: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/55.jpg)
– soil compaction:• at 30-40 cm depth
0,00,20,40,60,81,01,21,4
0 1 2 3 4 5 6 7 8Penetration resistance (MPa)
Dep
th b
elow
the
soil
surf
ace
(m)
0 10 20 30 40 50 60Soil moisture content (vol%)
Penetration resistance Soil moisture content
![Page 56: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/56.jpg)
0 5 10 15 20 25 30 35 40 45 50Horizontal distance (m)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
Hei
ght a
bove
the
refe
renc
e le
vel (
m)
temporary saturated zonepermanently saturated zoneequipotential linegroundwater tableequipotential head value (m)2.0
soil compaction hampers infiltrationto deeper soil layers
runoff
erosion
saturation of topsoil
![Page 57: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/57.jpg)
0,000,020,040,060,080,100,120,140,160,180,20
4:03 6:33 9:03 11:33 14:03 16:33 19:03
runo
ff (m
m)
0
0,1
0,2
0,3
0,4
0,5
0,6
rain
fall
(mm
)
runoff rainfall
saturation of topsoil
![Page 58: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/58.jpg)
![Page 59: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/59.jpg)
LS – Slope-length factor
• expresses the effect of topography
A
L
A
S
![Page 60: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/60.jpg)
USLE:
LS = (λ/22.1)m (65.41 sin2θ + 4.56 sinθ + 0.065)
λ = slope length (m)θ = angle of slopem = 0.5 if percent slop is < 5%, 0.4 on slopes of
3.5-4.5%, 0.3 on slopes of 1-3% and 0.2 on slopes < 1%
RUSLE: uses four separate slope length relationships
![Page 61: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/61.jpg)
Experimental models: USLE
• Value obtained from nomograph
![Page 62: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/62.jpg)
Experimental models: USLE
• Non-uniform slopes:– Slope is divided in n segments with uniform slope– For each segment: topographic factor calculated– Total topographic factor:
with (Li/22,13)mi.si = topographic factor(Li)(1-(Li-1/Li)Mi+1 = weight factor
( ) 11
1)/(1()()13.22/(/1 +
−
=
=
−⋅⋅⋅⋅=⋅ ∑ ii miiii
ni
i
min LLLSLLSL
![Page 63: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/63.jpg)
Experimental models: USLE
• After re-arranging:
with Ln = total slope lengthLi = length from top of slope to bottom of segment ili = length of segment iSi = slope factor of segment isi = slope of segment i (%)mi = slope length exponent
( )
065.00454.00065.0
)13.22()(/1
2
1
11
1
++=
−⋅⋅=⋅ ∑=
=
+−
+
iii
mni
i
mi
miin
ssS
LLSLSL iii
![Page 64: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/64.jpg)
Experimental models: USLE
• Exercise:Calculate LS for a uniform slope of 12 % and contour bunds at 20 m spacing.
Formula:
( )20065.0045.0065.013.22
ssxLSn
++⎟⎠⎞
⎜⎝⎛=
![Page 65: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/65.jpg)
Experimental models: USLE
• Exercise:Calculate LS for a uniform slope of 12 % (= 7°) and contour bunds at 20 m spacing.
LS = 1.46
( )20065.0045.0065.013.22
ssxLSn
++⎟⎠⎞
⎜⎝⎛=
![Page 66: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/66.jpg)
![Page 67: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/67.jpg)
C – Crop-management factor
• expresses degree of soil loss compared to clean-tilled fallow
• varies from near 0 (very well protected soil) till 1.5 (finely, tilled fallow surface)for clean-tilled fallow surface: C = 1
![Page 68: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/68.jpg)
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1
bedekkingsgraad
sedi
men
tcon
cent
ratie
bed
ekt/o
nbed
ekt
.
Influence of soil cover on sediment concentration (Rose, 1994)
soil cover
sedi
men
t con
cent
ratio
n co
vere
d/un
cove
red
![Page 69: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/69.jpg)
– types of soil cover• protection of soil by potato, sugar beets
and maize is rather limited due to the low amounts of crop residues and stem flow (maize)
• sowing of grass under maize, double drilling, green manure
• mulching
![Page 70: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/70.jpg)
•USLE: distinction between
–forest (e.g. C = 0.001 if 90% of soil surface covered by humus); values from tables
–pasture (e.g. C = 0.003 for grass with 95% of cover); values from tables
–cropland: different growth stages are considered; each with different % of surface cover and multiplied with the monthly fraction of annual Re.g. development stage is June: CJune = 0.5 x RJune
![Page 71: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/71.jpg)
mulch
![Page 72: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/72.jpg)
Mulching: crop residues corn
![Page 73: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/73.jpg)
– Field plot measurements (Nukerke, Belgium):
• 1 March -3 April 2001: 91 mm rain• 98 % less soil loss by green manure
(rye grass, 60 % cover)
0
0.5
1
1.5
2
2.5
3
3.5
blanco gg g
sedi
men
tver
lies
(kg/
100
m²)
0
2
4
6
8
10
12
14
16
runo
ff (m
m)
sedimentrunoff
soil
loss
(kg/
100
m²)
![Page 74: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/74.jpg)
• 84 to 99 % less total phosphorus losses by green manuring
0
1
2
3
4
5
6
7
blanco gg g
P ve
rlie
s (g
P/1
00 m
²)
DPPPTP
P lo
ss (g
P/1
00 m
²)
![Page 75: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/75.jpg)
• 79 to 98 % less nitrate losses (NO3-N + NO2-N) and 64 to 94 % less ammonium losses (NH4-N)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
blanco gg g
N v
erlie
s (g
N/1
00 m
²)
NO3-N + NO2-NNH4-N
N lo
ss (g
N/1
00 m
²)
![Page 76: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/76.jpg)
• RUSLE:
C = PLU x CC x SC x SR
PLU= prior land useCC = crop canopySC = surface coverSR = surface roughness
C is calculated and weighted at 15-day intervals
![Page 77: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/77.jpg)
P – Supporting practice factor
• expresses degree of soil loss compared to up-and-down-hill culture
• max. P-value = 1
• values for contouring, strip cropping, terracing, conservation practices, … from tables;
e.g. contouring on 9 to 12 % slope: P = 0.60
![Page 78: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/78.jpg)
• soil tillage– to retain crop residues at the surface– to increase soil biological activity– tillage practices:
• conventional tillage• no tillage• reduced tillage• subsoiling• contouring
![Page 79: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/79.jpg)
No tillage
![Page 80: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/80.jpg)
Subsoiling
![Page 81: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/81.jpg)
subsoiling
![Page 82: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/82.jpg)
Difference in soil moisture content after conventional (left) and reduced tillage (right)
![Page 83: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/83.jpg)
• grass buffer strips– do not prevent soil erosion on site but reduce off site effects– slow down runoff⇒ deposition of sediment
![Page 84: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/84.jpg)
![Page 85: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/85.jpg)
![Page 86: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/86.jpg)
– Measurements on field plots (Nukerke, Belgium):• 12 to 16 February 2001: 26,7 mm rainfall• 94 % less soil loss • 93 % less runoff
02468
1012141618
0 2 5 10
lengte grasstrook (m)
sedi
men
tver
lies
(kg/
100
m²)
0
5
10
15
20
25
runo
ff (m
m)
sedimentrunoff
length grass strip (m)
soil
loss
(kg/
100
m²)
![Page 87: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/87.jpg)
– Measurements on field plots (Nukerke, Belgium):• 93 % less total P-losses
05
101520253035404550
0 2 5 10
lengte grasstrook (m)
P ve
rlie
s (g
P/1
00 m
²)
DPPPTP
length grass strip (m)
P lo
ss (k
g/10
0 m
²)
![Page 88: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/88.jpg)
![Page 89: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/89.jpg)
Small and large scale hydraulic structures
• terraces, dikes, reservoirs and retention ponds
→ to protect villages, channels, ...
![Page 90: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/90.jpg)
bunds
![Page 91: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/91.jpg)
retention ponds
![Page 92: 1867-68 College of Soil Physicsindico.ictp.it/event/a06222/material/4/63.pdf1867-68 College of Soil Physics Donald Gabriels 22 October - 9 November, 2007 Dept. Soil Management Ghent](https://reader035.vdocuments.mx/reader035/viewer/2022063010/5fc3d2df41616f46de13c048/html5/thumbnails/92.jpg)
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