Soil Agrodiversity An Aspect of Farmers’ Management
of Biological Diversity
Michael Stocking
Associate Scientific Co-ordinator
UNU/UNEP PLEC Project
& Professor of Natural Resource Development
University of East Anglia, Norwich, UK
PLEC/UNU/UNEP - Montreal Symposium - Managing Biodiversity in Agricultural Systems, November 2001
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Enough bad news stories…...
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Agrodiversity - a good news story
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Objectives
(1) Explain what is meant by soil agrodiversity
- and show how it is a subset of agrodiversity,
but putting a principal focus on the soil system,
its functions and management.
(2) Identify field indicators for assessment of
soil agrodiversity - these are from the
perspective of the land user and focus on soil
and production variables.
(3) Describe the beneficial attributes of soil
agrodiversity - especially the ones that farmers
say they appreciate.
(4) Give examples of soil agrodiversity - in
protecting environments and supporting
livelihoods
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1. What is soil agrodiversity?
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Mainly spatial variations
Mainly temporal variations
Climatic Variability:
Macro- and meso-climate
Cycles and random trends
Droughts, floods
Biophysical Diversity:
Natural
Soils, productivity
environment
Plants, biota
Water, microclimate
Organisational Diversity:
Modified
Household characteristics
environment Resource endowments
Farm organization
Related
development
issues
Demography:
Population
Migration
Gender, age
Management Diversity:
Local knowledge
Adaptations and innovation
New technologies
Agro-Bio-Diversity:
Use and management of
species
Production, conservation
Macro-economy
Government services
Subsidies, aid, taxation
Livelihoods:
Poverty and food security
Sustainability
The AGRODIVERSITY Framework
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A focus on aspects of the soil
Environmental Variability:
Impact of environmental
change - droughts; floods &
soil’s role in mitigating
Biophysical Diversity:
Inherent soil properties
– natural fertility,
structure, water-holding
Organisational Diversity:
Soil resource endowments
- matching crop varieties to
soil type & position in
landscape
SOIL
AGRODIVERSITY
Agro-Bio-Diversity:
Use and management of
soil conserving
species
Management Diversity:
Local knowledge of soil,
management of fertility,
improvement of quality,
application of technology
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A definition of soil
agrodiversity
The diverse ways farmers manage their soil
resources for production, reproduction and
livelihood. Involves ….
☺
inherent soil fertility
☺
changes in soil quality brought about by
exogenous factors (e.g. climate change)
☺
soil conservation techniques
☺
local soil management knowledge
☺
soil value - economically, culturally
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2. Field Indicators for soil agrodiversity
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Gaining a Farmer Perspective
Farmers’ Domain
farmer-perspective
on-site
Professional Domain
BIOPHYSICAL
ASSESSMENT
• erosion assessment
• erosion impact
• soil variables
SOIL
PRODUCTIVITY
ASSESSMENT
• soil quality change
• yield change
• effect on future
yields
•
ECONOMIC
ANALYSIS
investment
appraisal
• returns to
labour
BIOPHYSICAL
MODELS
OUTPUTS
TO
PLANNERS
AND
POLICY
MAKERS
ECONOMIC
MODELS
The interaction area of principal interest in this paper
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Advantages of Farmer-Perspective
Field Techniques
Three main advantages:
(1) Realistic - less interventionist; more
likely to use indicators that farmers also use
(2) Integration - brings together wide variety of
processes to measure their sum effect;
especially important for soil quality changes.
(3) Practical - captures the long experience of
the land user, and farmers’ own experiments.
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New
Publication
Earthscan,
London
169pp. - 2001
ISBN 1 85383 831 4
Draft available on-line at:
www.unu.edu/env/plec
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Soil indicators - Sri Lanka Hill Lands
Crop growth changes
according to erosion
Soil surface indicators:
micro-pedestals, rills,
armour layer
Variable soil depth
on terrace
Build-up of soil behind
Gliricidia hedge
Compare soil colour
between eroded and
non-eroded parts
Locally adapted
techniques of soil
management
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3. Beneficial attributes of recognising
soil agrodiversity
Site benefits - increase in soil
resilience
Management and organisation easier practices
Landscape and social - diversify
local economy
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Site-based Benefits
Increase in resilience to continuing
land use and ability to continue
producing
Ability to withstand severe external
shocks - drought, floods……..
Utilises soil’s intrinsic value enhanced fertility and quality
Increased efficiency in use of inputs
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These are the sort of
benefits that farmers
have told us they
appreciate
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4. Examples of soil agrodiversity from
East Africa
Siting of banana cultivars in SW Uganda &
support to rural livelihood
Resilience of mixed farming systems,
Ngiresi Village, Tanzania
Ngoro pits of SW Tanzania
Keeping certain trees in fields for soil
improvement, Embu, Kenya
Multi-purpose stone walls in fields,
Mbarara, Uganda
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Agrodiversity in Ngiresi, Tanzania
Northern Highlands of Tanzania
economically the most important highland
area in country
high population pressure & much land
fragmentation
mean farm size 1.8 acres (0.7 ha)
high degree of farmer experimentation,
especially as alternative to coffee
significant diversity: 21 different cropping
mixes among 30 sample farmers
high agro-biodiversity, with many local
cultivars of major & minor food crops, as
well as medicinal, ornamental and other
use species
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Soil conservation practices
Conservation Measure
Occurrences (n=69)
Flat
None
Gently
Sloping
Steeply
Sloping
Total
13
5
0
18
Fanya chini
8
8
17
33
Fanya juu
1
1
3
5
Grass contours (no construction)
6
5
1
12
Bananas planted in lines across
slope
1
0
0
1
29
19
21
69
Total
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Method
Occurrences (n=69)
Flat
Manure + weeds + crop residues
Gently
Sloping
Steeply
Sloping
Total
11
5
1
17
Manure + crop residues + weeds after rotting
4
0
3
7
Fertilisers on coffee and banana only + manure + crop
residues + weeds after rotting
2
0
0
2
Fertilisers + manure + crop residues + weeds after
rotting
1
2
0
3
Fertilisers + manure + weeds + crop residues
1
1
0
2
Fertilisers + manure + crop residues
3
0
1
4
Fertilisers + manure + weeds
0
1
0
1
Fertilisers + weeds
0
1
0
1
Fertilisers + weeds + crop residues
0
1
0
1
Fertilisers + crop residues + weeds after rotting
0
0
1
1
Manure + weeds
0
2
0
2
Manure
2
1
1
4
Manure + weeds and crop residues around banana and
coffee stems
1
0
0
1
Fertiliser + manure + weeds and crop residues around
banana and coffee stems
0
1
0
1
Manure + weeds + crop residues placed on fanya chini
0
1
1
2
Manure + crop residue
2
1
2
5
Crop residues + weeds after rotting
0
0
1
1
Manure + fertiliser
0
2
0
2
Weeds burnt and ashes spread on field
0
0
2
2
Chicken manure + weeds + crop residues
1
0
0
1
Manure + weeds buried
1
0
0
1
Weeds + crop residues
0
0
3
3
Weeds
0
0
2
2
None
0
0
3
3
Total
29
19
21
69
Soil fertility
maintenance
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Agrodiversity
link to
livelihoods
Different farmers have
different opportunities
sloping land affords
different challenges
poorer farmers have steepest
land, but often the greatest
agrodiversity
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Resource endowment & topography
100%
80%
Steep
60%
Gentle
40%
Flat
20%
0%
Rich
Average
Poor
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Soil agrodiversity - components,
implications, effects
Broad Group of
Soil Activities
Soil preparation
Soil-based activity
Effect on biodiversity
Implications for livelihoods
Soil tillage –
conventional ploughing
Generally negative in
suppressing weeds, humifying
soil organic matter, depleting
beneficial soil structure and
creating soil surface more
likely to erode
Positive – different plants
using different ecological
niches
Tillage requires capital outlay in
resources and substantial labour.
Soil surface formation
– micro-relief. E.g.
ridging practices
Soil surface plant
residues – including
conservation tillage
Soil organic matter
management
Incorporation of
residues
Green manuring and
biomass crops
Weed mulching and
weed fallow
Plant management
effects on soil
No-till and direct
drilling
Contour planting
Sediment traps –
structures or live
barriers
Water, nutrient and
sediment
management
Fertilisation – organic
or inorganic
Irrigation
Soil and water
conservation
structures
Positive – provides for richer
below-ground biodiversity, less
erodible soil and conducive
micro-climates.
Ambivalent – increases
humification of organic matter,
but decreases soil erodibility.
Soil biota may respond
positively in the short-term.
Positive – can greatly increase
soil organic matter and waterholding capacity with benefits
for soil quality and resilience.
Positive – increases organic
matter, reduces soil
disturbance and allows soil
recuperation.
As for ‘Soil surface plant
residues’
Positive – retains water and
sediment, reduces erosion
rate.
Ambivalent – creates new
fields at expense of loss of soil
from upper slopes. But net
economic benefit positive and
prevents further problems
downstream
Positive – increases potential
biomass and plant diversity.
Some chemical toxicity sideeffects possible with
inorganics.
Positive – increases potential
plant production and lengthens
growing season.
Positive – increases
productive potential by
retaining soil and water onsite.
Requires labour, but brings benefit
through better water infiltration and
plant cover. Indigenous systems,
such as zaï pits, have supported
livelihoods for centuries in difficult
environments
Helps to suppress some weeds and
reduce labour. In mechanised
systems, additional capital resources
necessary as well as herbicides.
Requires equipment. Residues no
longer available for domestic animals
– a negative impact for many tropical
smallholder farmers.
Takes land out of direct production –
but minimised if green manure grown
on residual soil water out-of-season.
Needs expenditure in seeds and
equipment.
Takes land out of production – but
low cost fallowing, with some
beneficial weed species.
As for ‘Soil surface plant residues’.
Direct drilling equipment expensive.
Low cost plant management option
with large pay-back in soil quality and
future yields.
Where used to trap sediment, large
increase in livelihood support giving
production where none had been
possible before. Investment of labour
and capital in building and
maintenance.
Labour and/or cost of inputs. Nutrient
additions of inorganics have
immediate effect but productivity
gains may not last.
Expensive to install and maintain.
Many associated problems of
maintenance and environmental
impacts such as salinisation.
Expensive to install and maintain.
Take the results from Ngiresi and
elsewhere, conclude that:
soil agrodiversity consists of a number
of broad groups of soil-related
activities.
There is an enormous variety of such
activities
They have different effects on overall
status of biodiversity
There are important implications for
livelihoods - many positive, but some
negative
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Final word
If we want our work on aspects of biological
diversity to be taken seriously, then we must
put our results in the context of
development and appropriate policy
responses.
One useful way of doing this is to focus on soil
agrodiversity; demonstrate how it supports
global agendas; show how it maintains local
livelihoods; and convince policy makers that
here is something worth protecting.
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