integrated soil fertility management: definition and impact on productivity and soil c

TSBF

Fertility

Soil Biology

B VanlauweTSBF-CIAT

Kenya, [email protected]

Integrated soil fertility management: definition and impact on productivity and soil C

ABSTRACT

Traditional farming systems in sub-Saharan Africa depend primarily on mining soil nutrients. The African GreenRevolution aims at intensifying agriculture through dissemination of Integrated Soil Fertility Management (ISFM). Inthis paper we develop a robust and operational definition of ISFM, based on detailed knowledge of African farmingsystems and their inherent variability and of optimal use of nutrients. We define ISFM as ‘A set of soil fertilitymanagement practices that necessarily include the use of fertilizer, organic inputs, and improved germplasmcombined with the knowledge on how to adapt these practices to local conditions, aiming at maximizing agronomicuse efficiency of the applied nutrients and improving crop productivity. All inputs need to be managed followingsound agronomic principles.’

Issues that will be covered in this paper include: (i) the use of mineral fertilizer and expected responses under varyingsoil conditions, (ii) the use of locally available organic inputs in combination with fertilizer, and (iii) the integration oflegume species in rice-based systems, including aspects of improved agronomy. Examples are given for specificAfrican farming systems with high potential for adoption of ISFM, including sorghum and millet based systems in theSahel, legume-maize systems in the savanna, and cassava-based systems in the humid forest. For each above theme,both issues of crop productivity and soil carbon stocks and dynamics will be covered. Finally, the conditions thatenable the adoption of ISFM, including access to markets and appropriate policy, are also discussed.

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TSBF

Fertility

Soil Biology

B VanlauweTSBF-CIATKenya, [email protected]

Integrated Soil Fertility Management: definition and

impact on productivity and soil C

Finally, fertilizer is back on the African research for development agenda! [though the pro-organic agriculture voice & no-to-fertilizer voices are still heard!] Statement in 1996 (Research Director, IITA): ‘You can’t include fertilizer in your work since farmers in Africa are not using fertilizer’ The Alliance for a Green Revolution in Africa (AGRA) (headed by K Anan): ‘By 2015, increase fertilizer use from 8 to 50 kg fertilizer nutrients/ha’ Soil health program of AGRA [50% improvedplants, 50% improved soils]

The opportunity…

Soils are old; limited rejuvenation

Production environment in Africa

Only about 10% of the arable land in use Production environment in Africa

Only about 10% of the arable land in use [ limited areas with large population densities]


Lack of infrastructure, market organizationProduction environment in Africa

Mombasa264 USD

Masaka(Uganda)421 USD

Internationalmarket

165 USD

Lack of infrastructure, market organizationProduction environment in Africa

Bukavu(DRCongo)

900 USD

Lack of favorable policy [e.g, Nigeria: subsidies have been on/off over the past 30 years]

Declining capacity in R&D for soil fertility mgt Insufficient investment in agricultural R&D Brain drain Climate change, drought Civil strifeHIV/AIDS, malnutrition Land tenure insecurityHigh inflation, low salaries Etc, etc, etc


FAO Index of Net Food Output per Capita, 1961-2000

80

90

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160

1961

1963

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1967

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1971

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1975

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1981

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1987

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1999

World E SE Asia South Asia Sub-Sahara

Current status of agriculture in Africa

Necessary components of ISFM1. Fertilizers are indispensable

Necessary components of ISFM2. Organic resources are limited but necessary

Crop Oilpalm Imperata Manureresidues leaves

Availability? Acceptability? Quality?

Necessary components of ISFM3. Improved germplasm enhances nutrient uptake

Necessary components of ISFM4. Fields are heterogeneous

Good soil – same farm

Poor soil – same farm

‘The application of soil fertility management practices, and the knowledge to adapt these tolocal conditions, which maximize fertilizer and

organic resource use efficiency and crop productivity. These practices necessarily

include appropriate fertilizer and organic inputmanagement in combination with the utilization of improved germplasm’

Definition of ISFM

Agronomic efficiency = [Increase in yield]/[Fertilizer nutrients applied]

Definition of ISFM

0500

100015002000250030003500400045005000

0 50 100 150 200

Fertilizer nutrients applied (kg/ha)

Cro

p yi

eld

(kg/

ha)

Agr

onom

ic e

ffici

ency

Currentpractice

Germplasm& fertilizer

+ Organicresource mgt

+ Localadaptation

Germplasm& fertilizer’



‘Full ISFM’Move towards ISFM

Increase in knowledge

Responsive soilsPoor, less-responsive soils

A

B

C

Yiel

d/ Average of 8 kg nutrients/ha Relatively poor AE due to

poor fertilizer management Lack of use of improved

germplasm

Current practice

Step 1: Fertilizer and germplasm

0

1000

2000

3000

low medium highmanage me nt

mai

ze y

ield

[kg

ha-1]

control (no fertilizer applied)fertilizer applied

Mai

ze g

rain

yie

ld (k

g/ha

)

Management regime

Management intensity (planting date, crop density and time of phosphorus application), Tinfouga, Mali (Bationo et al., 1997).

Early Specificvariety

Dualpurposevariety


Agr

onom

ic e

ffici

ency

Currentpractice



+ Localadaptation







A

B

C

Yiel

d/


Source: Vanlauwe et al, PLSO, 2010


0

5

10

15

20

25

30

Local Improved - OPV Improved -Hybrid

N-A

E (k

g gr

ain

kg-1

N)

AverageSED

Step 1: Fertilizer and germplasmSoil C issues Zimbabwe, clayey soils

Source: Zingore al, EJSS, 2005

Important research issues

Site (country) Fert Duration Organic C (g kg-1) years - Fert + Fert Diff.

Zaria (Nigeria) AS 15 3.1 3.4 -0.3Ife (Nigeria) AS 7 8.0 8.5 +0.5Ibadan (Nigeria) AS 5 8.7 10.5 +1.8Ife (Nigeria) AS 14 5.7 3.5 -2.2Bouaké (Côte d’Ivoire) Urea 20 13.5 8.3 -5.2Ibadan (Nigeria) Urea 5 8.7 9.0 +0.3Ibadan (Nigeria) Urea 14 5.9 5.8 -0.1Ife (Nigeria) Urea 14 5.7 8.0 +2.3Ibadan (Nigeria) CANa 5 8.7 10.4 +1.7Mokwa (Nigeria) CAN 12 3.1 3.3 +0.2Ife (Nigeria) CAN 14 5.7 6.5 +0.8

Soil C issues

Total millet dry matter yield as affected by long-termapplication of crop residues and fertilizer, Sadore, Niger

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

1982 1984 1986 1988 1990 1992 1994 1996Year

Tota

l mill

et d

ry m

atte

r (k

g ha

-1)

ControlCrop residuesFertilizerCrop residues + fertilizer

0

20

40

60

80

100

120

withoutcrop

residues

with cropresidues

Dry

mat

ter /

N a

pplie

d (k

g kg

-1)

Step 2: Combining fert and OM

Agr

onom

ic e

ffici

ency

Currentpractice



+ Localadaptation







A

B

C

Yiel

d/


Site (years) Source of organic matter

Organic C (g kg-1)

None Fert OM Fert +OM

Ibadan (10) ACa with Leucaena 5.9 5.8 9.7 9.3Ibadan (10) AC with Senna 5.9 5.8 10.0 9.7Ibadan (10) Rotation + Mucuna 5.9 5.8 7.4 8.3Zaria (45) External Manure 3.3 2.9 5.0 5.0Saria (18) External Manure 2.5 2.4 NA 3.5

Average 4.7 4.5 8.0 7.2

Step 2: Combining fert and OMSoil C issues

0

10

20

30

40

50

Soil

C (g

C k

g-1 s

oil)

Silt and clayMicroaggregatesMacroaggregates

Control T. diversifolia C. calothyrsus Z. mays

b

aa a

Soil C contents of three aggregate size fractions (macroaggregates (>250 µm), microaggregates (53-250 µm), and silt and clay (<53 µm)) after 3 years of 4 Mg litter-C ha-1 yr-1 input (no input, T. diversifolia, C. calothyrsus, and Z. mays) in a maize cropping system in Central Kenya.

Source: Gentile et al, 2010

Step 2: Combining fert and OMSoil C issues


Step 3: Adaptation to local conditions

0

500

1000

1500

2000

2500

3000

Infield Outfield

Con

trol

mai

ze y

ield

(kg

ha-1

)

SED

(a)

0

5

10

15

20

25

30

35

40

45

Infield Outfield

N-A

E (k

g gr

ain

kg-1

N)

SED

(b)

Step 3: Adaptation to local conditionsIF acid soil THEN apply limeIF soil crusting THEN superficial tillageIF plow layer THEN deep tillageIF drought THEN water harvestingIF … THEN …

Agr

onom

ic e

ffici

ency

Currentpractice



+ Localadaptation







A

B

C

Yiel

d/


Step 3: Adaptation to local conditionsOccurrence of non-responsive soils!

Agr

onom

ic e

ffici

ency

Currentpractice



+ Localadaptation







A

B

C

Yiel

d/


Agr

onom

ic e

ffici

ency

Currentpractice



+ Localadaptation







A

B

C

Yiel

d/

Increase in complexity

Agr

onom

ic e

ffici

ency

Currentpractice



+ Localadaptation







A

B

C

Yiel

d/

Increase in complexityComplete ISFM???- Improved fallows- Agroforestry systems- Biomass transfer systems- ???- ???

Agr

onom

ic e

ffici

ency

Currentpractice



+ Localadaptation







A

B

C

Yiel

d/

Increase in complexity‘Simple’ approaches - Demonstrations- Information folders- Diagnosis non-

responsive fields- Supply chain issues- [Partial] subsidy

Agr

onom

ic e

ffici

ency

Currentpractice



+ Localadaptation







A

B

C

Yiel

d/

Increase in complexityThe Malawi fertilizer subsidy programme- Fertilizer + seedstarter packs

- From net importer to net exporter (2006)-AE is 14 kg grain/kg fertilizer nutrient

Agr

onom

ic e

ffici

ency

Currentpractice



+ Localadaptation







A

B

C

Yiel

d/

Increase in complexity‘Simple’ approaches - Demonstrations- Information folders- Diagnosis non-

responsive fields- Supply chain issues- [Partial] subsidy

Intensive approaches- Farmer capacity- Farmer field schools- Interactive learning- Diagnosis SF status- Best-fit options- Extension training

An enabling environment for ISFM

AE within the ISFM is based on short term gains

Focus on productivity… but indications that soil C can also be increased (soil-based ecosystem services)

It is difficult to achieve complete ISFM; probablya realistic goal should be to ‘move towards’ rather than achieving complete ISFM everywhere

Local diagnosis is crucial for local adaptation

Limitations to the AE concept

1. This is the time for soil science and plantnutrition to show impact in Africa; ISFM will drive

investments in soil fertility focusing on resource-use efficient agriculture!

Take home messages



2. The AE concept works; fertilizer as an entry point

towards agricultural intensification in SSA

Take home messages





3. Moving towards complete ISFM: immediateimpact is possible while investments in capacitybuilding for complete ISFM are happening

Take home messages





3. Moving towards complete ISFM: immediateimpact is possible while investments in capacitybuilding for complete ISFM are happening

4. Creating an enabling environment for ISFMis at least as crucial as developing ISFM practices

Take home messages

1. Under which conditions (population, soil,markets, etc) can ISFM be the model forintensification?

Questions for a fruitful debate

1. Under which conditions (population, soil,markets, etc) can ISFM be the model forintensification?2. Is fertilizer a valid entry point to improve soilfertility and soil C status and ensure longer termproductivity increases?


1. Under which conditions (population, soil,markets, etc) can ISFM be the model forintensification?2. Is fertilizer a valid entry point to improve soilfertility and soil C status and ensure longer termproductivity increases?3. How do we diagnose and manage non-responsivesoils?


1. Under which conditions (population, soil,markets, etc) can ISFM be the model forintensification?2. Is fertilizer a valid entry point to improve soilfertility and soil C status and ensure longer termproductivity increases?3. How do we diagnose and manage non-responsivesoils?4. At which scale should ISFM recommendationsbe developed (variation at different scales)?


Thank you!Merci beaucoup!

Asante sana!

integrated soil fertility management: definition and impact on productivity and soil c

Technology

use of fertilizer

fertilizer use

appropriate fertilizer

isfm increase

use of mineral fertilizer

fertilizer voices

mining soil nutrients

adoption of isfm