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Combating desertification through direct seeding mulch-based cropping systems (DMC)

De
44 pages
This alternative solution of the conventional cropping systems in developing countries preserves and restores the fertility of agricultural soils. It combines two major principles: the soil is never tilled and is permanently covered by plants…
Raunet Michel and Naudin Krishna, 2006. Combating desertification through direct seeding mulch-based cropping systems (DMC). Les dossiers thématiques du CSFD. Issue 4. 40 pp.
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Issue 4
Combating Combating
ddesereserttification ification
tthrhroough direct seeding ugh direct seeding
mmulch-based ulch-based
crcroopping systems pping systems
(DMC)(DMC)
Comité Scientifique Français de la Désertification
French Scientific Committee on DeserCSFD
Les dossiers thématiques
du CSFD
French Scientific Committee on DesertificationIssue 4
The creation in 1997 of the French Scientific Committee on Managing Editor
Desertification (CSFD) has met two concerns of the Ministries in
Marc Bied-Charreton charge of the United Nations Convention to Combat Desertification.
President of CSFD First, CSFD materialises the will to involve the French scientific
Emeritus Professor at the University of Versailles
community versed in desertification, land degradation, and
Saint Quentin-en-Yvelines (UVSQ)
development of arid, semi-arid and sub-humid areas, in generating Researcher at the Centre of Economics and Ethics for
Environment and Development (C3ED-JRU IRD/UVSQ) knowledge as well as guiding and advising the policy makers and
actors associated in this combat. Its other aim is to strengthen the
position of this French community within the international context. In Authors
order to meet such expectations, CSFD is meant to be a driving force
Michel Raunet regarding analysis and assessment, prediction and monitoring,
Researcher at the Production and Transformation Systems
information and promotion. Within French delegations, CSFD also Department of the Agricultural Research Centre for
International Development (CIRAD-PERSYST) takes part in the various statutory meetings of the organs of the United
michel.raunet@cirad.fr Nations Convention to Combat Desertification: Conference of the
Parties (CoP), Committee on Science and Technology (CST),
Krishna Naudin
Committee for the Review of the Implementation of the Convention. It Researcher at CIRAD-PERSYST
krishna.naudin@cirad.fr also participates in meetings of European and international scope.
CSFD includes a score of members and a President, who are appointed Contributors
intuitu personae by the Minister for Research, and come from various
Marc Bied-Charreton, Emeritus Professor at UVSQ specialities of the main relevant institutions and universities. CSFD is
Olivier Husson, Researcher at CIRAD-PERSYST managed and hosted by the Agropolis International that gathers, in
Lucien Séguy, Resear
the French town of Montpellier and Languedoc-Roussillon region, a
large scientific community specialised in agriculture, food and
environment of tropical and Mediterranean countries. The Committee
acts as an independent advisory organ; it has neither decision-making
powers nor legal status.
Editing and iconography
Its operating budget is financed by subsidies from the French
Isabelle Amsallem (Agropolis Productions) Ministries of Foreign Affairs and for Ecology and Sustainable
agropolisproductions@orange.fr
Development. CSFD members participate voluntarily to its activities,
Design and production as a contribution from the Ministry for Research.
Olivier Piau (Agropolis Productions)
More about CSFD:
agropolisproductions@orange.fr
www.csf-desertification.org
agropolis productions
Photography credits
Danièle Cavanna (INDIGO picture library of the Institut
de recherche pour le développement, IRD) and
Jean Asseline (IRD) as well as the authors of the pictures
shown in this report.
Translated by David Manley
Printed by Les Petites Affiches (Montpellier, France)
Copyright registration on publication ISSN : 1772-6964
1,500 copies (also available in French)
© CSFD/Agropolis International, April 2007
Editing, production and distribution of Les dossiers thématiques du CSFD are ,Les dossiers thématiques du CSFD ar
fully supported by this Committee through the backing of relevant French For reference: Raunet M. et Naudin K., 2006. Combating desertification
through direct seeding mulch-based cropping systems (DMC). Les dossiers Ministries. Les dossiers thématiques du CSFD may be freely downloaded from the
thématiques du CSFD. N°4. April 2007. CSFD, Montpellier, France. 40 p.
Committee website.
une réalisationFo reword
ankind is now confronted with an issue Marc Bied-Charreton
of worldwide concern, i.e. desertifi cation, Emeritus Professor of the University of Versailles
Saint-Quentin-en-Yvelines (UVSQ) which is both a natural phenomenon and
Researcher at C3ED-JRU IRD/UVSQ Ma process induced by human activities.
(Centre of Economics and Ethics Our planet and natural ecosystems have never been so
for Environment and degraded by our presence. Long considered as a local
Development) problem, desertifi cation is now a global issue that affects
us all, including scientists, decision-makers, citizens from
both the South and North. Within this setting, it is urgent
to boost the awareness of civil society to convince it to get
involved. People must fi rst be given the elements necessary
to better understand the desertifi cation phenomenon and
the concerns. Everyone should have access to relevant
scientifi c knowledge in a readily understandable language
and format. Within this scope, the French Scientifi c
Committee on Desertifi cation has decided to launch a
new series entitled “Les dossiers thématiques du CSFD”,
which is designed to provide sound scientifi c information
on desertifi cation, its implications and stakes. This series
is intended for policy makers and advisers from the North
and South, in addition to the general public and scientifi c
journalists involved in development and the environment.
It also aims at providing teachers, trainers and trainees
with additional information on various associated fi elds.
Lastly, it endeavours to help disseminate knowledge on
the combat against desertifi cation, land degradation,
and poverty to stakeholders such as representatives
of professional, non-governmental, and international
solidarity organisations.
A dozen reports are devoted to different themes such as
biodiversity, climate change, pastoralism, remote sensing,
etc., in order to take stock of current knowledge on these
various subjects. The goal is also to set out ideological
and new concept debates, including controversial issues;
to expound widely used methodologies and results
derived from a number of projects; and lastly to supply
operational and intellectual references, addresses and
useful websites.
These reports are to be broadly circulated, especially
within the countries most affected by desertifi cation,
by e-mail (upon request), through our website, and
in print. Your feedback and suggestions will be much
appreciated! Editing, production and distribution of “Les
dossiers thématiques du CSFD” are fully supported by
this Committee thanks to the backing of relevant French
Ministries. The opinions expressed in these reports are
endorsed by the Committee.
Remote sensing, a support to the study and monitoring of the Earth environment 1Preamble
For decades, farmers in many regions have had to deal Jean-Yves Grosclaude
with serious soil erosion problems—water erosion Director of the Department
of Rural Development, Environment during every rainfall, wind erosion, which blows away
and Natural Resources, the soil and generates dust clouds, with an impact that
French Development Agency (AFD) reaches far beyond the initial areas. Everyone remembers
the dust bowl process, which darkened the skies over the
grain fi elds of the Great Plains in USA and Canada during
the 1930s. Everyone also knows about the devastating
effects of erosion on the Loess Plateau in China.
Excessive tillage, scarce and poorly distributed water,
much of which is lost via runoff, has prompted research
on alternative cropping systems, designed especially to
stall erosion and runoff, promote rainwater infi ltration
and offset climatic hazards.
In the 1960s, this gave rise to farming practices combining
two concepts: minimal tillage and direct seeding in
mulch of residue from the previous crop. This movement
started in USA, developed and gained momentum in
Brazil and then spread to Latin America and Australia.
It subsequently took root in Asia, Europe (including
France), and then Africa and Madagascar. Now more
than 90 million ha are cultivated without tillage and
direct seeding on mulch. In the 1980s, in the Brazilian
cerrados and small family farming areas, CIRAD and
its Brazilian partners managed to adapt direct seeding
principles for application in tropical farming conditions.
This has renewed the hopes of smallholders, for whom
the soil is a farming resource that has to be sustainably
preserved.
These new practices represent more than just a set of
techniques, they call for a real change of spirit, because
ploughing—a historical mainstay of agriculture—must
be abandoned. Research is currently under way,
especially in North Africa (Tunisia), sub-Saharan Africa
(Cameroon), Madagascar, Vietnam, Laos and Cambodia.
For almost 10 years, AFD (French Development Agency),
FGEF (French Global Environment Facility) and MAE
(French Ministry of Foreign Affaires) have been backing
the process of adaptation and dissemination of this
“sustainable agriculture”, within the framework of rural
development projects carried out under a range of
agroecological and socioeconomic conditions. This novel
agricultural approach brings a solution that is especially
suitable for farming in fragile ecosystems with a high risk
of desertifi cation.
th This 4 Dossier thématique du CSFD clearly showcases
direct seeding mulch-based cropping systems, including
the challenges, diffi culties and prospects. I am sure
that many readers will be won over, since these new
systems represent a keystone for sustainable agricultural
development—preserving natural resources, which
nurture all rural activities in developing countries.
2 Combating desertification through direct seeding mulch-based cropping systems (DMC)Table of Contents
4 30
New farming practices needed Four years of participative experiments
in regions affected by desertification with farmers on DMC cotton crops
in northern Cameroon
6
Soil and water in desertification conditions 36
DMC: a promising approach
14 for combating desertification?
DMC: an alternative to conventional cropping systems
in desertification-stricken countries
38
18 For further information...
DMC benefits for farmers
40
22 List of acronyms
Cumulative effects and services of DMCs and abbreviations
for landscapes and communities
Table of Contents 3New farming practices
needed in regions affected
by desertification
esertification has a serious impact on water,
soils, biodiversity, agrarian systems,
and in turn on the people who live off the D services provided by agroecosystems.
st century, Climate change has been worsening in the 21
thus broadening the range of desertification, environ-
mental degradation processes in arid, semiarid
and subhumid-dry regions. Family farms in Southern
countries will have to adapt—technically, economically
and strategically—to be able to survive.
The soil is often the only capital that farmers have in
these regions, and this resource is essential to the func-
tioning and resilience of agroecosystems: it should
thus be preserved and enhanced. Water is a scarce and Current agricultural systems (combined with livestock
uncertain resource in countries affected by desertifica- farming) are not very productive or diversified, and crop
tion: most of it disappears via runoff and evaporation. It yields are highly irregular in semiarid and subhumid
should be preserved to benefit soil-plant systems, thus environments. Rural communities are barely able to
enhancing plant biomass production. live off these systems, so malnutrition and endemic
Glossary
Action research: Participative applied research involving or adverse change (in a scope and setting to be specifi ed: for
development stakeholders and farmers. a soil, this could involve a loss of biodiversity and resilience,
leading to structural breakdown), in a soil or landform, of various
Agroecology: A current research and engineering stream of processes and a change in environmental conditions (climate,
thought and action whereby production systems and subsectors vegetation, water regime, humans, etc.) relative to the initial
are approached from a joint ecological and agricultural pers- genesis conditions.
pective to promote sustainable development and environmental
protection. Fertility: Ability of a soil to produce under its climate.
Agroecosystem: An ecosystem that is utilised for agri- Agrarian system: Spatial expression of the association
cultural production. of farmers and techniques implemented by a rural society to
fulfi l its needs.
Biodiversity: Biological diversity, or biodiversity, refers to
the variety or variability of all living organisms. This includes Productivity: Potential ability of an organism (plant or ani-
genetic variability within species and their populations, the mal) to provide a certain amount of a specifi c product (whole
diversity of associated species complexes and their interactions, plants, fruit, seeds, fodder, fi bre, oil, wood, milk, meat, wool,
and that of ecological processes they affect or with which they etc.) relative to a spatial or temporal unit.
are involved (IUCN defi nition, 1988).
Resilience: Ability of a system to withstand disturbances
Biomass: Total mass of living cells from a given site relative in its structure and/or functioning and, when these are over-
to the area or volume. come, to get back to a state that is comparable to the initial
situation (Ramade, 1993). In summary, it is the ability to buffer
Degradation: This term generally means “slow destruction” disturbances.
4 Combating desertification through direct seeding mulch-based cropping systems (DMC)Focus
Desertification briefly
The United Nations Convention to Combat Desertification,
drawn up in 1994, defines desertification as “land desertification
in arid, semiarid and dry subhumid areas resulting from several
Eroded landscape. Neghelle. factors, including climatic variations and human activities”.
Southern Rift Valley,
Ethiopia. © M. Raunet
The desertification concept, like the closely linked land and
ecosystem degradation concept, derives from the overall
famines are often widespread in these areas. Under negative qualitative viewpoint that underlies insidious complex
such conditions, agro-socioeconomic sustainability processes (natural and human-induced) which are hard to
overcome, combining causes, effects and consequences, along seems unfeasible, and farmers, who are struggling to
with many feedback loops. These processes have climatic, simply fulfil their immediate needs, obviously cannot
ecological, agricultural, economic and social aspects—with this be very concerned about safeguarding the environment
latter factor being associated with the use and sharing of scarce and natural resources.
resources (wood, fertile soils, water, rangelands, wild game,
etc.) because of excessive pressure on these resources or very The rapid degradation trend that comes with deserti-
high human population concentrations.fication can only be stalled by promoting the creation,
adaptation, development and large-scale dissemina-
The desertification concept is also implicitly associated with the tion of new sustainable agrarian systems, especially
drought concept, thus with the scarcity and irregularity of water those combining cropping and livestock production.
supplies at crucial times, but also, conversely, with excessive or These positive interventions could be developed and
heavy rainfall that induces damage (waterlogging of crops, implemented through action research, with farmers
destructive mechanical effects, silting of structures, etc.). This involved at all development stages.
land and ecosystem degradation occurs concomitantly to
disruption of the ecological balance and involves a reduction The principles of an agroecologically-oriented “new
in ecosystem productivity, i.e. the fertility of soils, plant agriculture” involving synergetic “soil-water-biomass-
cover, rangelands, biodiversity, etc. In addition, there are biodiversity” interactions are presented in this dossier:
ecoclimatic and human dimensions, i.e. excessive anthropogenic direct seeding mulch-based systems (DMC). The under-
pressure, difficulty in living and producing in such ecosystems, lying principles and features are discussed, along with
risks, poverty, need for adaptation, etc.the direct effects and indirect benefits that both farmers
and communities can expect on different scales (field,
Rural people require an adaptive control strategy to overcome this farm, village land, territory).
imbalance and degradation, including better risk management
and, if possible, a scheme to ensure agroecosystem regeneration
and enhanced resilience. The resilience concept is pivotal to the
desertification process. Desertification could be considered
as equivalent to a loss of resilience resulting from combined
ecoclimatic and human stress. Conversely, “backtracking”
(regeneration) by human means (e.g. new cropping practices)
will result in a resilience gain (recuperation). The resilience of an
agroecosystem is the foundation of its sustainability.
New farming practices needed in regions affected by desertification 5 Soil and water
in desertification
conditions
esertification is not directly associa-
ted with annual rainfall levels. The
desertification process can, for instance, D occur when the soil and vegetation
Sheet and “lavaka” (deep gully) erosion conditions are degraded but there is 1,400 mm of annual
in the Hauts-Plateaux region of Madagascar.
precipitation. Desertification is, however, directly © M. Raunet
linked with the fact that for various reasons (e.g.
capped soils) rainfall does not (or no longer does)
penetrate into the soil enough to adequately nourish
crops, rangelands and natural vegetation.
The shortage of water percolating through the soil
is mainly due to the physical and organic quality of
degraded soils and the low level of plant cover, thus
increasing the vulnerability of these soils to clima- In dry tropical regions, sandy to sandy-loamy soils,
tic stress (e.g. heavy precipitation). This is a typical which generally have a very low organic matter content
situation where the causes and effects are mutually (0.3-1% in the top 20 cm layer), to fragile soils with very
involved in a process that has no clear onset. A small- little structure, are conventionally cropped after scra-
scale (realistic, yet metaphorical) model of this process ping and pulverization of the soil surface (tillage to 8-
is the ordered contraction of the vegetation cover in 10 cm depth). The soils are then left bare, which makes
striped bush (vegetation/soil complex alternating them even more vulnerable to sealing and sheet ero-
shrub thickets and bare areas in a clumped and/or sion, thus maintaining or even worsening the impact
striped pattern) on glacis in semiarid regions. These of desertification.
vegetation strips correspond to areas where water
infiltrates, and the bare patches are integral runoff Leaching is very common to 20-40 cm depth, corres-
areas where the desertification process has begun. The ponding to the maximal water percolation depth. In
functioning of this striped structure, and the way it this layer, which is sandier or loamier than the under-
develops once it begins, are quite well known. Little is lying layer, and waterlogged during heavy rainfall, the
known, however, about the onset of the process, how it water flows “hypodermically” in a lateral direction,
is triggered or the thresholds beyond which it begins. leading to the formation of a small perched water
layer which surfaces quickly to merge with the heavy
Poor, fragile and unproductive soils surface runoff. This causes temporary waterlogging of
root systems, which are asphyxiated, just at the time
In semiarid and subhumid dry, so-called degraded when they are also hampered by drought if it has not
areas, water does not percolate to deep soil horizons rained for a week! These beige-, grey- or pink-coloured
because of the poor soil structure (so-called conti- soils are called “leached tropical ferruginous soils”.
nuous or massive structure) due to the extreme lack When the leached layer settles, through a sudden dis-
of organic matter. The soil also has low porosity or continuity, on a more clayey and compact substrate
is completely sealed close to the surface by kaolinic that water and roots cannot penetrate, these are called
clays, iron oxides and quartz sand which act like solid planosols (like the famous sterile degraded hardé soils
concrete. of northern Cameroon).
6 Combating desertification through direct seeding mulch-based cropping systems (DMC)Focus
Striped bush, a striking vegetation
facies common to the Sahel
The “striped bush” ecosystem is typical of the vegetation found degradation (Ichaou, 2000). After onset of the process, it
on relatively regular landscapes along glacis, with slopes of less proceeds via positive feedback (with trapping of plant
than 2%, in the Sahel or along the northern edges of Sudanian- debris, sediment and seeds), thus inducing auto-reinforcement
Sahelian regions. This ecosystem includes strips or arc-shaped of the striped shrub stands.
areas of vegetation, often regularly-spaced shrub thickets of
variable width growing parallel to relatively continuous contour
lines. These vegetation strips are interspersed with bare strips of
land with very little plant cover -so it is also called “contracted
vegetation”. These ecosystems can be structured in lines, arcs or
rosettes. This type of vegetation is also found beyond Africa, in
other semiarid environments in Australia, Mexico, Madagascar,
etc.
This type of vegetation adaptation and contraction is noted
in areas under low rainfall regimes (300-700 mm/year) but
where violent sporadic storms occur with subsequent intense
sheet runoff. These vegetation stands are the result of a tradeoff
between the soil, climate, vegetation and human activities. The
striped stands offset the low rainfall conditions and enable the
vegetation to develop under a priori unfavourable ecological
conditions (300-400 mm/year of rainfall). Contracted systems
common to unfavourable climatic areas recreate, by their
structure, ecological conditions resembling those that occur in Stripped bush on the Sofi a Bangou plateau near
Banizoumbou (60 km east of Niamey, Niger). more favourable areas that receive 800 mm/year of rainfall!
The soil is ancient hardpan laterite with a thin layer of very clayey loose
These higher productivity levels go against the opinion that soil (0-60 cm thick), with low organic matter content in bare strips and
a high content in strips of vegetation.these systems have developed as a response to environmental
© J. Asseline and J.L. Rajot
Soil and water in desertification conditions 7Focus
Degradation of intertropical soils:
farming practices have to change!
Land began seriously degrading in the tropics and subtropics in
the 1960s as a result of the population boom and land saturation,
with a concomitant shortening of fallow periods in savanna
areas and forest reconstruction in humid areas. This degradation
included all types of erosion, compaction and hardsetting,
leaching, acidification, organic matter loss, uncontrollable weed
invasion, etc., thus resulting in overall degradation of soil fertility.
This situation will undoubtedly worsen yearly due to climate
change if effective solutions are not found. Despite increased
awareness on this process, initiatives required under suitable
socioeconomic conditions to overcome this feedback-type soil
degradation spiral have not been applied on a large scale.
Agricultural sustainability is inevitably linked with the
sustainability of soil fertility—which is essential for crop
production. Soil protection is thus a major economic challenge.
Striving to preserve and improve soils helps fight poverty.
Paradoxically, economists and policymakers are often unable
to assess a soil before or after cultivation, or to forecast the
outcome after a certain period of use. Development economists
classify the soil under general non-renewable natural resource
management issues, despite the fact that it is theoretically a
lasting resource, in contrast with other resources (water, forests,
fish, rangelands, etc.). The soil can be assessed according to its
quality, as much or even more than its quantity. This quality is
called “fertility”, which humans can degrade or regenerate.
It should be kept in mind that farmers do not degrade soil
fertility by pleasure, lack of awareness or without realizing
it, but unfortunately because they have no other choice. The
pressure on the land becomes too heavy and the farmer’s plans
for the future are dictated by his/her short-term survival needs.
Medium and long-term prospects are too remote, especially
since the farmer often has no investment potential. In this
deadlock situation, farmers of the South will have to change
their practices, often drastically, and they should be assisted via Gully erosion in a sisal plantation.
Rift Valley, Ethiopia. development-oriented research. This is top priority.
© M. Raunet
8 Combating desertification through direct seeding mulch-based cropping systems (DMC)

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