Mr. Iaaich Hamza, National Institute of Agricultural Research (INRA), Morocco. Global Symposium on Soil Erosion (GSER19), 15 - 17 May 2019 at FAO HQ.

1. No-Till Effect On Soil Erosion In Mid-
Slope Cropping Through Soil Aggregates
Stability And Fallout Radionuclides
Hamza Iaaich1, Rachid Moussadek1, Rachid Mrabet1, Bouamar Baghdad2, Moncef
Benmansour3, Anis Zouagui3, Nezha Aserar4, Elouadihi4, Abdelhaq Bouabdli4
1National Agricultural Research Institute (INRA), Morocco, 2Hassan II Institute of
Agronomy and Veterinary Medicine (IAV Hassan II), Morocco, 3National Center on Energy
and Nuclear Science and Techniques (CNESTEN), Morocco, 4IbnTofail University, Faculty
of Science, Kenitra, Morocco
CONCLUSION
The study indicates that the no-till system is
helping creating better soil particle cohesion
and thus reducing soil erodibility.
This attests of the effectiveness of
Conservation Agriculture as a package for
enhancing soil aggregate stability and
reducing soil erosion impact in mid-slop
cropping.
Figure 1. Structural stability test results
Table 1. FRNs test results
ACKNOWLEDGEMENT
The study was held within the frame of the
International Atomic Energy Agency (IAEA)
RAF project N°5063. The team is thankful to
the IAEA staff for the technical and financial
support.
INTRODUCTION
Soil structural stability is an important
physical parameter that reflects soil
erodibility. It indicates the soil particles’
capacity to conserve proper arrangement
when faced to splash or humectation
phenomena (Le Bissonnais, 1996).
Another soil erosion indicator is the flux of
indicating fallout radioneclides (FRN). Three
FRNs are used as tracers of soil erosion or
accumulation: 137Cs, 7Be and 210Pbex (Walling
et al. 1995, Mabit et al. 2008, IAEA. 2014).
These FRNs have half-life cycles running
from 40 days (for 7Be) to100 years (for
210Pbex), allowing soil erosion and
accumulation assessment within time scales
of rainfall event using 7Be to more than a
century using 210Pbex. Several researches used
FRNs based techniques for soil erosion
quantification (He and Walling. 1997, Gaspar
Ferrer. 2012, Benmansour et al. 2012).
In this study, we approached soil erosion in a
mid-slop Vertic Regosol using structural
stability and two FRNs (137Cs and 7Be) on two
experiment sites with two cropping systems
(no-till and conventional tillage). The aim is
to assess the impact of no-till system and
conservation agriculture, as mean to enhance
physical soil properties such as soil organic
matter content, structural stability and
erodibility.
MATERIALS AND
METHODS
The study area is located in the North-West of
Morocco (5°39’ W;35°35’ N) sub-humid
undulating landscape. The experiment plot is
of one hectare, with a slope gradient of 5%
and a cereals-legumes rotation on no-till
(NT). We tested the effect of no-till with an
adjacent plot with conventional tillage (CT)
under the same conditions, using two
indicators: Aggregate structural stability (Le
Bissonnais, 1996) and FRNs (137Cs and 7Be).
For the structural stability, we applied the
test on three undisturbed samples from
each plot (NT and CT) to calculate the mean
weighted diameter (MWD) resulting from
three stability tests for the 2-5mm soil
fraction: (i) rapid humectation, simulating
the effect of intense rain (ii) slow
rehumectation, simulating soil behavior
under moderate rainfall (iii) desagregation
for testing soil particle cohesion.
Concerning the 137Cs and 7Be flux, we
compared the activity along the two study
sites (NT and CT plots) to their activity in a
stable reference site. The reference site for
the 137Cs is a neighboring forest, while that
of 7Be is a neighboring stable unexploited
site. For both reference sites, we used a grid
sampling of nine samples to the depth of 1m
for the 137Cs and 40cm for the 7Be. These
depth are the maximum reached by each
FRN, where we can identify the
radionuclide’s general activity and profile
distribution. For the study sites, we used a
transect approach of five samples with a
10m incrementing. The FRN activities were
identified by Gamma HPGe spectrometry.
Mass balance conversion models were used
to convert activites to soil loss rates.
MAIN RESULTS
The average MWD is of 2,18 mm for the NT
plot and 2,02 mm for the CT plot. This
indicates a higher soil aggregates stability
and thus a reduced particles detachability
under no-till system.
The FRN flux shows a similar pattern,
where 7Be activity showed that the NT plot
retained 74,6% of the reference site activity,
while the CT plot retained 58,1%. As for the
137Cs, the NT plot retained 20,7% of the
reference site activity while the CT one
retained 18,5%. We used the mass balance
II conversion model for the resulted
activities. The conversion model showed
that the NT plot generated 5,4% less soil
loss rate compared to the CT one.