The document discusses approaches for developing soil fertility management recommendations based on analyses of soil and agronomic data. It describes different methods including soil testing, diagnostic trials, agronomic trials, and decision support systems. The goal is to identify soil health constraints, determine limiting nutrients, establish appropriate fertilizer application rates, and develop individualized recommendations for farmers. The document emphasizes developing recommendations that account for variability in soils, crops, and farming conditions.

1. Soil Fertility Management
Recommendations
A framework for the analyses of soil and
agronomic data to develop
recommendations for ISFM
E. Jeroen Huising
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2. Fertilizer and ISFM recommendations
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Inputs (nutrients, water, labour, agro-chemicals,
energy etc.)
Desired
Outputs
(e.g. Yield)
or
Undesired
Outputs
(e.g. N loss,
GHG loss)
0
1000
2000
3000
4000
5000
6000
7000
0 50 100 150 200
Fertilizer N applied (kg N ha-1
)
Yield(kgha-1
)
0
20
40
60
80
N-AE(kg(kgN)-1
)
grain yield
AE
(a)
N response curve and N agronomic efficiency
 Fertilizer recommendations – aiming to maximize yield or economic return,
assuming risks are low (optimum economic and biophysical conditions and good
management – e.g. limited cost for obtaining capital)
 ISFM – Aiming at maximizing agronomic efficiency assuming resource constraints
and accounting for the farming conditions of smallholder farmers in Africa.

3. Providing solutions to problems with
soil – crop productivity
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Where?
Assessment of soil
fertility status and
diagnosis of soil health
problems
For What?
To improve crop
productivity; Assess
crop requirements,
yield gaps etc.
For Whom?
Who has to implement;
Assess the socio-
economic conditions
(GL  GR)  E  M]
Environment
Management
Germplasm – Genetic
potential
Context
Problem
Targets

4. Potential is not the problemPotential is not the problem!

5. Finding solutions to soil health
problems
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Identify (soil health) problem
Identify (alternative) solutions
Recommended option
Decision/ Testing
Implementation
Monitoring and evaluation
From ‘best-bet’ to ‘best fit’;
Testing technology and management options on farmer’s
fields;
Stepwise approach to
full implementation of ISFM

6. Integrated Soil Fertility Management
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7. Specificity of the recommendation
GRADIENTS
Country wide
Crop
Farming community
One particular management
aspect (e.g. fertilizer)
Site specific
Specific crop, type,
variety, cropping system
Individual farmer
Several management aspects
(integrated – or systems) (e.g.
integrated nutrient
management)
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



Embracing and understanding
variability; spatial and
temporal; what is the
probability of farmers
benefitting

8. Levels of sophistication - complexity
• Rule of thump
• Expert knowledge (Look-up tables; soil
suitability ranking)
• Empirical models (making use of agronomic
trials and using statistical models)
• Deterministic models (DSSAT, APSIM, crop
growth simulation models
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9. 0
1000
2000
3000
low medium high
manage me nt
maizeyield[kgha
-1
]
control (no fertilizer applied)
fertilizer applied
Maizegrainyield(kg/ha)
Management
intensity
(planting date,
crop density,
time of P
application);
Tinfouga, Mali
Bationo et al.,
1997
Universal principles of nutrient management

10. Responsive and Non-responsive soils
I. Poor non-responsive soils
II. Poor responsive soils
III. Fertile non-responsive soils

11. From diagnosis to management
options (best-bets)
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X
XX
XXX
X X XXCrop constraints
Management constraints
Nutrient limitations
Soil health constraints
Poor,
non-
responsive
soils
Responsive
soils
Fertile,
non-
responsive
soils
Attainable yield under rainfed conditions
Potential yield for selected crop for area
under consideration
Agro-climatic constraints
Crop variety or cultivar selection
Water harvesting & irrigation (semi-)
permanent structures
Improved agronomic practices
Nutrient management recommendations
Soil improvement
Diagnostic phase Management options

12. Practical Definitions for Responsive
and Non-Responsive soils
• Soils that respond to N, P or K (individual or in combination) only are
called responsive soils; Soils that show a limitation in any of the three
nutrients, but not in any other. These limitation may be solved easily with
readily available fertilizers
• Soils that are responding well to application of meso- or secondary
nutrients (Mg, Ca, S) are called intermediate responsive soils
• Soils that show clear limitations in micro-nutrients and show little or no
response to application of macro and secondary nutrients are called non-
responsive soils
• Soils that show little response to macro and meso fertilizer application
associated with clear limitations in soil organic matter (clear response to
manure application), and/or soil acidity (strong response to lime
application), and/or any constraints related to water retention and/or
constraints towards root development are likewise call non-responsive
soils
• Based on the above several response classes could be defined
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13. Different approaches; Making
recommendation based on soil testing
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Soil Test
Critical
Values
Calculate nutrient
requirements;
recommend fertilizer
application (crop
specific)
Testing/evaluation
in farmer’s fields
(populations
studies)
Soil test
values/ soil
information
Soil testing
(soil test kits,
mobile labs,
soil labs)
• Aims to give fertilizer recommendation based on soil test values; uses soil test
interpretation guide to classify nutrient status of the soil, use crop nutrient
requirements (or nutrients removed by the crop) to determine nutrient
requirement and modified by soil nutrient status to determine application
requirement. Gives indication of possible or likely nutrient limitations
• Is (semi-)quantitative approach; not very accurate or precise; will not predict
response accurately; will not capture spatial variability adequately; is simple to
understand and use, might be costly if sampling of all farmers field is required
• Possible improvements, soil test kits might provide alternative, however soil
nutrient classes could be predicted from improved soil mapping techniques; use
models to more accurately predict fertilizer response.

14. Diagnostic trials to determine soil
health constraints
• Nutrient omission trials to determine limiting nutrients (N,P and K,
and others as individual nutrients or as complex/compound, e.g.
micronutrients), added with treatment like manure, and/or liming
• Identifies limiting nutrients and degree of nutrient limitation,
identifies constraints related to SOM and soil acidity.
• Is quantitative: determines attainable yield level under optimal
management; allows for calculation of AE and results can be used
for calibration of models like QUEFTS
• Multi-location trials allows for determining response classes and
assessment of soil fertility status in the region
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Nutrient
omission trials
(diagnostic)
Attainable
yield, Soil
health
constraints,
nutrient
limitations
Soil Response
Category/ Yield
gaps
Soil fertility
management strategy,
based on soil response
class and evidence
Agronomic survey;
establish yield gaps
on farmers fields

15. There marked differences in response patterns between sites;
six response classes distinguished, but…
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Non Resp - Fert
Non Resp - Poor
Poor Resp. – low fert.
Resp – N&P, intermed fert
Resp. – P&N
Resp – N, rel. fert.

16. Input (nutrient) response trials
• Determines response to varying rate of input
application (nutrients, manures, inoculants, other);
allows for recommendation of fertilizer applications
rates and optimum rates for highest AE
• Requires insight in limiting nutrients and other soil
health constraints; not suited for diagnostic purposes
• Very strong if includes variety trials to select best yield
varieties under good management
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Agronomy
trials, variety
and nutrient
response trials,
including soil
amendments
Crop
response to
nutrient
application
and soil
amendments
Interaction
between various
crop production
factors: GxExM
Best bet technology,
Area specific fertilizer
recommendation;
improved agronomic
efficiency
Demonstration
plots, testing on
farmers fields

17. Expert systems / Decision Support Systems for
making recommendations to individual farmers
Concept based on:
• Indigenous soil nutrient
supply
• Fertilizer nutrient recovery
• Internal nutrient use
efficiency
• Potential yield/attainable
yield
• Nutrient uptake curve
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18. Soil Test
Critical
Values
Calculate nutrient
requirements;
recommend fertilizer
application (crop
specific)
Testing/evaluation
in farmer’s fields
(populations
studies)
Soil test
values/ soil
information
Soil testing
(soil test kits,
mobile labs,
soil labs)
Nutrient
omission trials
(diagnostic)
Attainable
yield, Soil
health
constraints,
nutrient
limitations
Soil Response
Category/ Yield
gaps
Soil fertility
management strategy,
based on soil response
class and evidence
Agronomic survey;
establish yield gaps
on farmers fields
Agronomy
trials, variety
and nutrient
response trials,
including soil
amendments
Crop
response to
nutrient
application
and soil
amendments
Interaction
between various
crop production
factors: GxExM
Best bet technology,
Area specific fertilizer
recommendation;
improved agronomic
efficiency
Demonstration
plots, testing on
farmers fields
QUEFTS – empirical model
Decision support tools (DSSAT, APSIM)
Data and information
Knowledge /
interpretation Recommendations and learning
Expert systems/
DST; nutrient
manager
Individual and specific
recommendations. Crop
choice; alternative
solutions, farm
management
C
o
m
p
l
e
x
i
t
y
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19. Diagnosis of
soil health constraints
Diagnostic phase
Type of constraint Variable Analyses and interpretation
(explanatory variables, co-variates)
Agro-climatic and agro-ecological
constraints
(Ypot,c - Ymax,i),
((Ypot,c-Ymax,i)/Ypot,c)
Rainfall distribution, Rooting depth
restrictions, Topographic position,
Water supply.
Soil related constraints:
responsive and non-responsive soils
(YNPK,i-Ycon,i)/(Yatt,i-Ycon,i),
(Yatt,i-Ycon,i), (Yatt,i – YNPK,i)
SCSI, Land degradation index (LDI),
pH, CEC, ExAC, etc. spectra
For responsive soils:
Limiting nutrients: K
P
N
YNPK,i-YNP,i; ((YNPK,i-YNP,i)/(YNPK,i-Ycon,i))
YNPK,i-YNK,i; ((YNPK,i-YNP,i)/(YNPK,i-Ycon,i))
YNPK,i-YPK,i; ((YNPK,i-YNP,i)/(YNPK,i-Ycon,i))
SOM, pH, Minerals, CEC, AEC
For non-responsive soils:
Limiting secondary and
micro-nutrients
YNPK+X,i-YNPK,i,> 0;
(YNPK+X,i-YNPK,i)/(YNPK+X,i-Ycon,i)
YNPK+OM,i-YNPK,i> 0
(YNPK+OM,i-YNPK,i)/(YNPK+OM,i-Ycon,i)
Soil weatherable minerals, Low or
high Zn, B, Cu, SOM quality
Soil structure limitations; water
retention and water holding capacity
YNPK+OM,i-YNPK,i > 0
(YNPK+OM,i-YNPK,i)/ (YNPK+OM,i-Ycon,i)
YNPK+X-YNPK ≤ 0
Soil texture, SOM, SCSI
Soil chemical constrains YNPK+Lime,i-YNPK,I> 0
(YNPK+Lime,i-YNPK,I)/(YNPK+Lime,i-Ycon,I)
YNPK+OM,I-YNPK,I> 0
YNPK+X,I-YNPK,I> 0
pH, ExAC,
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20. Soil test
values/ soil
information
Soil testing
(soil test kits,
mobile labs,
soil labs)
Nutrient
omission trials
(diagnostic)
Attainable
yield, Soil
health
constraints,
nutrient
limitations
Agronomic survey;
establish yield gaps
on farmers fields
Agronomy
trials, variety
and nutrient
response trials,
including soil
amendments
Crop
response to
nutrient
application
and soil
amendments
Demonstration
plots, testing on
farmers fields
Data and information
C
o
m
p
l
e
x
i
t
y
Protocols
Data collection templates
Legacy data
Data and information
Databases – Meta data standards5/24/2015 ISFM data management and analysis WASHC Training Workshop 20

21. What soil and land data do we need to make
ISFM recommendation using the different
approaches
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Laboratory
Cost!
Time!
Test kits
Accuracy?
Cost?
Local
indicators
Sensitivity?
Extrapolation?