Assessing soil erosion and conservation with various methodologies at different scales
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Assessing soil erosion and conservation with various methodologies at different
scales
SymposiumAssessing benefits of SLM-Key for success Rabat 2009
MOROCCAN DESIRE TEAM
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Sehoul is located between Oued Bouregreg and Grou
is part of the natural geographic unit " Plateau Central Marocain".
Marginal land with a high rate of poverty and important indicators of
degradation
Land degradation, characterized by high variability and chronic shortage in term of natural resources.
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Crop rotation Cereal /
leguminous
Fodder cultivation: e.g. the lupine
Rainfed tree plantation: olive
associated with annual cultivation
Assisted regeneration of cork oak
The assessed approaches
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METHODOLOGY
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Results
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Crop rotation: Cereal / Leguminous
1- Increased soil protection by providing better cover
2- Maintaining and improving soil fertility
Cereal / leguminous rotation vegetation cover reached 65,5%
Cereal / Cereal rotation vegetation cover is < 50 %
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3- Improving soil structural stability
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bean/wheat wheat/bean Wheat/chick peas oats / wheat Barley/barley
Compaction Capacity Penetrometr (Kg/cm3)
Mecanic Resistance Torvan (Kg/cm3)
Fig.1: Compaction capacity penetrometr and mecanic resistance torvan in various rotation types
Kg/cm3
Crop rotation (cereal/leguminous): Improves soil resistance to compaction and limits surface crusting.
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(%)
-
2,0
4,0
6,0
8,0
10,0
12,0
bean/wheat wheat/bean Wheat/chickpeas
oats / wheat Barley/barley
Fig.2: Moisture conten in various rotation types
4- Soil moisture
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The Rainfed fruit tree plantation associated with annual cultivations
1- Protecting the soil surface (vegetation cover)
In the olive grove (15 years), we recorded the most important herbaceous cover (66%). However, the average cover of herbaceous in the rotation Cereal / Cereal does not exceed 52,5%.
2- Improvement of soil fertility and surface characteristics
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olive parcel of 15years
olive parcel of 7 years wheat Barley
Moisture Content (%) organic matter (%)
(%)
Fig.3: Moisture content and Organic matter
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Fodder cultivation: (the
lupine)
0102030405060708090
100
Matorral Fallow (10 years) Fallow Lupin
herbaceous Litter bare soil(%)
Fig.11: Soil Cover
Lupin: offers the best vegetation cover
(%)
0,00
0,50
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Matorral Fallow (10years)
Lupin Fallow oats Barley
Fig.13: Organic matter
Offers a medium organic matter content in the soil.
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Assessment of soil erosion by 137Cs measurements
barley/wheat rotation leguminous/ wheat rotation vine monoculture
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barley/wheat rotation
Wheat / leguminous
rotation
Vine monoculture
Mean erosion (tha-1yr-1)
12.5 2 8
Less erosion forwheat /leguminous crop rotation
Medium term assessment of Erosion rates ~50 years
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Rainfall simulation technique: Soil loss and runoff coefficient under different land use
Novembre 2007 Avril 2008
Coefficient Ruissellement
en %
Taux d'érosion
(g/m²)
Coefficient Ruissellement
en %
Taux d'érosion
(g/m²)
Sol fersialitique
Labour 1,5 2,5 *** ***
Chaume pâturé 8,6 17,6 *** ***
Jachère annuelle *** *** 3,3 1,76
Jachère longue 6 5,8 6,3 2,6
Céréale *** *** 1,7 0,2
Nu très caillouteux *** *** 25 205
Sol Calcimagnésique
Jachère 6,6 24 9 55,4
Parcours *** *** 17,8 37,8
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HYDROLOGIC MEASUREMENTS/ THE Hannanat catchement
Water balance in 2008-2009
rainfall 726,7mm
Runoff coefficient : 10%
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Follow-up of the vegetation growth and effect on runoff
Variation du couvert végétal au niveau du microbassin Hannanat
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14/10/2008 25/10/2008 12/11/2008 11/12/2008 09/01/2009 09/02/2009 17/03/2009 24/04/2009
% c
ou
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rt
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Céréales
Fève
jachère
Inculte
Vigne
Autumn Winter Spring
Rainy events with important runoff
22 31 1
Rainy events without runoff
14 20 8
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Hydrologic behaviour at the experimental micro catchment :
Réponse hydrologique du bassin à l'évènement pluvieux du 1/12/09 (automne)
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Déb
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Déb
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Débit liquide (l/s)
Intensité(mm/h)
Autumn winter
•In autumn: the flood hydrograph shows a quick response. The peak discharges are around several hundreds of liters per second (469 l/S) with a Runoff coefficient up to 54%.
•In winter : rainfall events are longer and complicated compared to the autumnal period. Most of rainfall events shows a runoff coefficient lower than 5%.
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The high content of suspended load during the intense rain events
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Surface runoff and erosion modelling Our will is to model the Surface runoff, using a
Model (for example the LISEM). This modelling will permit to imagine scenarios of
functioning of the watershed in relation with the global changes expected to be recorded in the area, first the scenario of success of the WSC actions our team is implementing, but also other scenarios of change like climatic change or land use and land cover transformations.
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Conclusion
Study of vegetation cover, soil fertility, soil texture and moisture.
Use of 137Cs measurements
Soil loss and runoff coefficient
Crop rotation Cereal /
Leguminous seems to be a good strategy
to use in Sehoul
But there is need for providing fodder
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Study of Water balance
Hydrologic behavior
Enable to understand the soil
behaviour at the catchment scale and
to evaluate the global soil loss
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Thank you