Principles of Integrated Soil Fertility
Management (ISFM)
Africa Soil Health Consortium
2013
Introduction to ISFM as a concept
Objectives
• Understand the history of soil fertility management
• Understand why ISFM is needed for smallholder
farmers in sub-Saharan Africa
• Understand the individual components of ISFM and
their interactions with each other
• Understand the variability between farms and the need
for local adaptation of nutrient input recommendations
• Understand the concept of agronomic efficiency
• Understand the concept of economic efficiency
History of soil fertility management
Approach: external
input use
Approach: organic
input use
Approach: organic
input use & fertilizer
Approach:
integrated soil
fertility
management
Fertilizer: +++
Organic inputs: -
Fertilizer: Organic inputs: +++
Fertilizer: +
Organic inputs: +++
Fertilizer: ++
Organic inputs: ++
Limited success,
shortfalls in
infrastructure and
farming systems
Limited adoption,
organic matter
production requires
land, labour and/or
livestock
Localized adoption
around specific
crops
Goal of large scale
adoption
1960s and 1970s
1980s
1990s
2000s
Focus on mineral fertilizer
Adding nutrients: The ‘Green Revolution’
• A success in Asia and Latin America
– External input use (mineral fertilizers & lime)
– Improved varieties
– Irrigation
• A disappointment in sub-Saharan Africa
– Fertilizer is ‘too costly’
– Fertilizer use is uneconomic in poorly responsive environments
– Fertilizer recommendations were not tailored to farmer’s
specific circumstances
• Heterogeneous soil fertility
• The farmer’s social and economic situation and goals
Focus on organic resources
• Conserving nutrients: through compost and manure
• Recycling nutrients : through deep rooting trees
• Adding nitrogen: through biological N2 fixation (BNF) by leguminous cover
crops, trees, shrubs and grain legumes
Disadvantages:
• Quality of organic resources is often poor
• Quantity of manure or organic resources is not sufficient
– Competing uses for plant residues
• Organic materials are bulky and costly to store, transport and apply
• Adoption and suitability of leguminous cover crops is limited by
(1) high labour requirements
(2) only N can be supplied
(3) availability of other nutrients (e.g. P)
need to be sufficient for effective BNF
(4) drought and low soil pH limit BNF
(5) lack of useable yield (grain
legumes excepted)
When unsufficient nutrients are
added to maintain soil fertility:
downward spiral into a poverty trap
Integrated Soil Fertility Management
‘A set of soil fertility management practices that necessarily
include the use of fertilizer, organic inputs and improved
germplasm combined with the knowledge on how to adapt
these practices to local conditions, aiming at optimizing
agronomic use efficiency of the applied nutrients and
improving crop productivity. All inputs need to be managed
following sound agronomic and economic principles.’
Yield = G (genotype) x E (environment) x M (management)
Principles of production ecology
Yield = G (genotype) x E (environment) x M (management)
Defining factors
YP = G x E
Limiting factors
YW = G x E x M (water)
Reducing factors
YA = G x E x M (water) x M (nutrients,
pesticides, weeding, etc)
Components of ISFM
Yield = G (genotype) x E (environment) x M (management)
Seeds should be adapted in terms of
• Responsiveness to nutrients (M)
• Adaptation to the local environment (E)
• Resistance to pests and diseases (E)
Components of ISFM
Yield = G (genotype) x E (environment) x M (management)
Mineral Fertilizers:
• Supplement recycled or added
nutrients from organic sources
• Contain essential nutrients in a
form readily available for plant
uptake.
Organic inputs:
• Source of nutrients, including nutrients
not contained in mineral fertilizers
• Replenish soil organic matter
• Increase the crop response to mineral
fertilizer
• Improve availability of phosphorus for
plant uptake
• Regulate soil chemical and physical
properties
• Create a better rooting environment due
to the improvemnet of the soil structure
• Improve the soil’s capacity to store
moisture
• Maintain the biodiversity in the soil
Positive interaction: fertilizer – organic matter
With organic matter
Yield (kg/ha)
Without organic matter
C
A
B
Fertilizer input (kg/ha)
Positive interaction:
fertilizer – organic matter
Long term effect of fertilizer and
crop residues on millet grain yield
in Sadore, Nigeria
Exercise
1. What can you conclude from this
figure?
2. What do you still have to take
into account before making
recommendations based on this
figure?
Effect of fertilizer (60 kg N, 13 kg P and 25 kg
K/ha from NPK (17:17:17 and urea) on grain
yield of 2 local and 2 improved maize
varieties in south Kivu, DR Congo.
1. All varieties had
larger yields when
fertilizer was applied
2. Highest yields with
fertilized hybdrids
4. Yield from
unfertilized BH540
was slightly higher
than fertilized local
varieties
3. Yields more than
doubled when both
fertilizer and improved
germplasm was used
Local adaptation
Variability between farms
Variability between farms
• Goals and objectives
• Importance of off-farm
income
• Amount of production
resources available to invest
in the farm
–
–
–
–
–
Land
Labour
Animal manure
Crop residues
Cash
Tittonell et al. (2008)
Local adaptation
Variability between fields
Soil fertility gradients
within farms:
- Fertile home fields
- Degraded outfields
Responsive
Responsive
(in-field)
(in-field)
Less-responsive
Less-responsive
(outfield,
(outfield, couch
couch grass
grass infestation)
infestation)
Unresponsive
Unresponsive
(degraded
(degradedsoil)
soil)
Low or no response:
- Fertile in-fields, due
to high amounts of
nutrients applied in
the past
- Degraded soils
- Weed infested fields
Variable responses to nutrient inputs
Tittonell and Giller (2013)
The response to seed
and fertilizer inputs is
large in responsive soils
The response to seed and
fertilizer inputs is small in
unresponsive soils
Organic resources are
needed to make efficient
use of fertilizer and
improved seeds in
unresponsive soils
Agronomic efficiency (AE)
The amount of additional yield
obtained per kg nutrient applied
AE = (YF-FC) / Xappl
YF: Yield in treatment with
nutrient application
YC: Yield in control treatment
Xappl: the amount of nutrient X
applied (kg nutrient/ha)
Increasing AE
To increase AE (and yield) at a particular fertilizer
application rate:
•
•
•
•
Plant the crop at the right planting density
Apply fertilizer at the right time
Apply fertilizer in the right place
Apply fertilizer in several split applications
Sound agronomic principles
Maximum return to investments and high AE need
good crop management with:
•
•
•
•
•
•
•
Appropriate varieties
Appropriate land preparation
Spacing
Planting dates and practices
Weeding
Pest and disease management practices
Appropriate intercropping arrangements
Sound economic principles
Comparing the value of additional yield with the costs of the inputs required
ISFM – From poverty traps towards an African Green Revolution?
Exercise
1. Calculate the agronomic efficiency:
- applying 100 kg fertilizer per ha
- applying 200 kg fertilizer per ha
2. Calculate the value:cost ratios for:
- Increasing yields from point B to
point C
- Increasing yields from point C to
point D
3. Is it economically sound to increase
yields up to point E with the use of
fertilizer?
Coordinates
Prices
The price of N fertilizer is 1 US$/kg Point A: (0, 500)
4. What happens to the maximum
Point B: (50, 2300)
Yield can be sold for 0.5 US$/kg
economic yield when the price of
Point C: (100, 3000)
fertilizer increases?
Point D: (150, 3300)
Point E: (200, 3380)
Exercise: From poverty traps towards an African Green Revolution?
Sounds perfect!
But: how easy is it to reverse the
downward spiral into an upward spiral?
Exercise: Think about two factors that
could constrain this process.
Exercise: From poverty traps towards an African Green Revolution?
Storing and marketing produce is often
problematic so the foreseen impacts in
terms of increased income and food
security cannot be taken for granted.
It takes several years for a degraded
soil to become productive and
responsive again. How does the
farmer finance the rehabilititation of
his/her field?
The problems with availability of
fertilizer and organic inputs from the
1970s and 1980s have not yet
overcome.
ISFM is very important, but interventions in the political and economic
environment are needed to make ISFM work!