Principles of Integrated Soil Fertility Management (ISFM)

Africa Soil Health Consortium2013

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

2000s1990s1980s1960s and 1970s

Approach: external input use

Fertilizer: +++Organic inputs: -

Limited success, shortfalls in infrastructure and farming systems

Approach: organic input use

Fertilizer: -Organic inputs: +++

Limited adoption, organic matter production requires land, labour and/or livestock

Approach: organic input use & fertilizer

Fertilizer: +Organic inputs: +++

Localized adoption around specific crops

Approach: integrated soil fertility management

Fertilizer: ++Organic inputs: ++

Goal of large scale adoption

Focus on mineral fertilizerAdding 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 (4) drought and low soil pH limit BNF (2) only N can be supplied (5) lack of useable yield (grain (3) availability of other nutrients (e.g. P) legumes excepted) need to be sufficient for effective BNF

Nutrients from outside the farm are needed!

Need to integrate fertilizer and organic resources!

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)

YP = G x E

YW = G x E x M (water)

YA = G x E x M (water) x M (nutrients, pesticides, weeding, etc)

Defining factors

Limiting factors

Reducing factors

Components of ISFMYield = 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 ISFMYield = 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

Fertilizer input (kg/ha)

Yiel

d (k

g/ha

) Without organic matter

With organic matter

A B

C

Long term effect of fertilizer and crop residues on millet grain yield in Sadore, Nigeria

Positive interaction: fertilizer – organic

matter

Exercise

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. What can you conclude from this figure?

2. What do you still have to take into account before making recommendations based on this figure?

2. Highest yields with fertilized hybdrids

3. Yields more than doubled when both fertilizer and improved germplasm was used

4. Yield from unfertilized BH540 was slightly higher than fertilized local varieties

1. All varieties had larger yields when fertilizer was applied

Local adaptationVariability 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 adaptationVariability between fields

Soil fertility gradients within farms: -Fertile home fields-Degraded outfields

Low or no response:-Fertile in-fields, due to high amounts of nutrients applied in the past-Degraded soils-Weed infested fields

Responsive (in-field)

Less-responsive(outfield, couch grass infestation)

Unresponsive(degraded soil)

Unresponsive(degraded soil)

Responsive (in-field)

Less-responsive(outfield, couch grass infestation)

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)

YF: Yield in treatment with nutrient applicationYC: Yield in control treatment

Xappl: the amount of nutrient X applied (kg nutrient/ha)

The amount of additional yield obtained per kg nutrient applied

AE = (YF-FC) / Xappl

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 principlesComparing 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?

4. What happens to the maximum economic yield when the price of fertilizer increases?

CoordinatesPoint A: (0, 500)Point B: (50, 2300)Point C: (100, 3000)Point D: (150, 3300)Point E: (200, 3380)

PricesThe price of N fertilizer is 1 US$/kgYield can be sold for 0.5 US$/kg

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?

The problems with availability of fertilizer and organic inputs from the 1970s and 1980s have not yet overcome.

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?

Storing and marketing produce is often problematic so the foreseen impacts in terms of increased income and food security cannot be taken for granted.

ISFM is very important, but interventions in the political and economic environment are needed to make ISFM work!