Fertiliser use, soil responsiveness and yield gaps in cotton-based cropping systems of N Cameroon

(1)

Fertiliser use, soil responsiveness and

yield gaps in cotton-based cropping

systems of N Cameroon

Yield Gap Symposium, AGRO 2010 Montpellier

Michel Cretenet, Pablo Tittonell

CIRAD-Persyst

(2)

Background

• Cameroon National debt funds

(C2D)

: soil fertility restoration

project (SODECOTON, CIRAD)

• Price fluctuations lead to discontinuous/ insufficient

fertiliser use in the long term: impact on soil productivity

• Productivity decline in cotton-based cropping systems of

West and Central Africa: impact on regional economies

• What determines current yield gaps, how wide are they, and

how to close them?

(3)

500 750 1000 1250 1500 1750 2000 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 50 75 100 125 150 175 200

Decline in productivity

F

er

ti

lis

er

appl

ied (

k

g

ha

-1

)

S

eed

-c

otton

y

iel

d (

k

g ha

-1

)

Cotton yield and fertiliser use at national level

1

2 Year

500 750 1 000 1 250 1 500 1 750 2 000 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 50 75 100 125 150 175 200

F

er

ti

lis

er

appl

ied (

k

g

ha

-1

)

S

eed

-c

otton

y

iel

d (

k

g ha

-1

)

Cotton yield and fertiliser use at Garoua, N Cameroon

1

2 Year

Yield = 1520 – 18 t (r*

2

_{= 0.4)}

r2 = 0.7 r2 = 0.6 500 750 1 000 1 250 1 500 1 750 2 000 120 140 160 180 200 Period 1986-1996 Period 1997-2005

Fertiliser applied (kg ha

-1

₎

S

eed

-c

otton

y

iel

d (

k

g ha

-1

)

Global fertiliser productivity at Garoua, N Cameroon

1

2

(4)

Discontinuation

Restoration

Fertiliser use

C

rop pr

oduc

ti

v

it

y

(5)

Tittonell et al., 2008, Agronomy Journal 100

C

h

d

Manure + fertiliser application

B

iom

as

s

y

iel

d

(t

ha

-1

)

Time (seasons)

A

r

Manure application

“Hysteresis” of land rehabilitation - Kenya

(6)

Control

Mulch + Manure + Fertiliser

Restauration of control (M+M+F)

0 1000 2000 3000 4000 5000 0 5 10 15 20 0 5 10 15 20

Maize grain yield (kg ha

-1

₎

_{Seed-cotton yield (kg ha}

-1

₎

Time (yr)

La mémoire du sol…

Aplahoué, 1972 - 1993

0 25 50 75 100 0 5 10 15 20 0 25 50 75 100 0 5 10 15 20

Relative yields (%)

(7)

Closing yield gaps through fertiliser use

Network of on-farm trials in 1990

• Cotton response to mineral fertilisers (N,P,K,S)

• 250 farmer fields around Garoua (n = 135)

• Soils 20-30% Clay + silt; 650 ±80 mm

• 0, 125, 250, 375, 500 kg ha

-1

Average response to fertiliser by cotton in 1990

0

500 1000

1500

2000

2500

0

100

200

300

400

500 Observed

Model

Y = a + b e*

-x/185

Fertiliser applied (kg ha

-1

₎

S

eed

-cot

to

n

y

iel

d (

kg h

a

-1

)

a

b

n=7

n=34

n=66

n=31

n=6

0

500 1000

1500

2000

2500

3000

0

100

200

300

400

500 Response to fertiliser by cotton per quintile

Fertiliser applied (kg ha

-1

₎

S

eed

-cot

to

n

y

iel

d (

kg h

a

-1

)

(8)

50 60 70 80 90 100 0 500 1000 1500 2000 2500 0 10 20 30 40 50 Coarse sand Fine sand Clay + fine silt

5.1 5.4 5.7 6.0 6.3 6.6 6.9 0 500 1000 1500 2000 2500 0.00 0.01 0.02 0.03 0.04 0.05 pH (water 1:2.5) Exchangeable Al 0.3 0.5 0.7 0.9 1.1 1.3 0 500 1000 1500 2000 2500 0.0 1.0 2.0 3.0 4.0 Soil organic matter

Exchangeable Ca Exchangeable Mg Cation exchange capacity

0 5 10 15 20 0 500 1000 1500 2000 2500 0.0 0.1 0.2 0.3 0.4 0.5 Olsen P Exchangeable K

SOM

(%)

Cmo

l

(+ )

_kg

-1

m

g

P

k

g

-1

Cmo

l

(+ )

K k

g

-1

Cmo

l

(+ )

_Al

k

g

-1

p

H

s

c

a

le

C

la

y

+

s

ilt

(%)

C

oa

rs

e

s

a

nd

(

%

)

Seed-cotton yield without fertiliser (kg ha

-1

₎

Seed-cotton yield without fertiliser (kg ha

-1

₎

Soil productivity without fertiliser

Soil organic matter (%)

Y

iel

d w

it

ho

ut

f

er

ti

liser

(kg ha

-1

)

Qq1 Q1 Q2 Q3 Q4 Qq4

Yield = 5870 SOM - 2880

r

2

= 0.98

0 500 1000 1500 2000 2500 3000 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Closing yield gaps through fertiliser use

0 500 1000 1500 2000 2500 3000 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 Early sowing Modal sowing Late sowing

Management practices affect attainable yields

Soil organic matter (%)

S

eed

-cot

to

n

y

iel

d (

kg h

a

-1

)

(9)

Soil carbon losses and productivity decline

A positive feedback

• Clearence of native savannah vegetation

• Continuous cultivation with poor C restitution

• Soil physico-chemical degradation

• Productivity decline (less biomass, less soil cover, less C back to soil)

Productivité et durabilité dans les savanes cotonnières d’Afrique de l’Ouest

Récolte

CO₂

Matière Organique du Sol 15-35 T minéralisation photosynthèse Humification K₁15-40% Résidus de Culture 1-3 T 1.5-4T 0.6-1 T K₂6% CO2 0 2 4 6 0 20 40 60 80 100 Age de défriche Teneur en carbone (mg/g) horizon 0-20 cm

Valeurs obtenues par analyse

Valeurs simulées par le modèle

0 2 4 6 0 20 40 60 80 100 Age de défriche Teneur en carbone (mg/g) horizon 0-20 cm

Valeurs obtenues par analyse

Valeurs simulées par le modèle

Système de culture et matière organique du sol

0 500 1000 1500 2000 2500 3000 F0 F1 F0 F1 F0 F1

résidus exportés résidus restitués res.rest.+ pailles

re

nde

m

e

nt

k

g/ha

0.60 0.70 0.80 0.90 1.00 1.10 1.20

M

O

S%

mais 72-80 coton 72-80 moy 0-30 cm

Exportation de résidus de récolte

0 500 1000 1500 2000 2500 3000 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Yield without fertiliser Attainable yield (full fertiliser)

0 500 1000 1500 2000 2500 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Fertiliser use efficiency Yield gap

Response parameters, efficiency, yield gaps and soil organic matter

Soil organic matter (%)

S

eed

-cot

to

n

y

iel

d (

kg h

a

-1

)

(10)

Local land use systems

• Organic matter and nutrient flows at village scale

• Land tenure, diversity of livelihoods and ethnicity

• How to determine reference yield levels (potential?) over such

heterogeneous agricultural landscapes?

National policies with local consequences

(11)

Diversity at local scale: how to define yield potential?

Debru, J. (2009) L’abandon de la culture du cotonnier est-il momentané ou définitif ? AgroParisTech

History of land occupation and use: current heterogeneity

Diversity of farming trajectories and styles

N

um

ber

of

l

iv

e

s

k

heads

(12)

Concluding remarks

• Discontinuous/ insufficient fertiliser use widens yield gaps

through cumulative effects

• Lack of reversibility in fertiliser response beyond a certain

threshold of soil degradation – hystereis or la mémoire du sol

• Soil organic matter as key to restoring soil productivity, but

complexity of local land use systems must be embraced

• Policy innovation: e.g. could policy enforce crop rotations

or fallows?

(13)

(14)

N

um

ber

of

l

iv

es

k

heads

(15)

(16)

National policies with local consequences

• Faible intégration dans l’enseignement

• 5 juillet 2010

(17)

Decline in productivity

500 750 1 000 1 250 1 500 1 750 2 000 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 50 75 100 125 150 175 200

F

er

ti

lis

er

appl

ied (

k

g

ha

-1

)

S

eed

-c

otton

y

iel

d (

k

g ha

-1

)

Cotton yield and fertiliser use at Garoua, N Cameroon

1

2

(18)

r2 = 0.7 r2 = 0.6 500 750 1 000 1 250 1 500 1 750 2 000 Period 1986-1996 Period 1997-2005

Discontinuous fertiliser use

Fertiliser applied (kg ha

-1

₎

S

eed

-c

otton

y

iel

d (

k

g ha

-1

)

H

Period 1986-2007 r2 = 0.8 r2 = 0.7 500 1000 1500 2000 500 1000 1500 2000 Garoua Est Garoua Ouest

Yields N Cameroon (kg ha

-1

₎

Y

ie

ld

s

tu

dy

r

eg

io

n

(

k

g

h

a

-1

)

0

500 1000

1500

2000

2500

0

100

200

300

400

500 Observed

Model

Y = a + b e*

-x/185

(19)

Average response to fertiliser by cotton in 1990

0

500 1000

1500

2000

2500

0

100

200

300

400

500 Observed

Model

Y = a + b e*

-x/185

Fertiliser applied (kg ha

-1

₎

S

eed

-cot

ton

y

iel

d

(kg ha

-1

)

a

b

(20)

n=7

n=34

n=66

n=31

n=6

0

500 1000

1500

2000

2500

3000

0

100

200

300

400

500 Response to fertiliser by cotton per quintile

Fertiliser applied (kg ha

-1

₎

S

eed

-cot

ton

y

iel

d

(kg ha

-1

)

(21)

Soil productivity without fertiliser

Soil organic matter (%)

Y

iel

d w

it

hout

f

er

ti

liser

(

kg

ha

-1

)

Qq1 Q1 Q2 Q3 Q4 Qq4

Yield = 5870 SOM - 2880

r

2

= 0.98

0 500 1000 1500 2000 2500 3000 0.4 0.5 0.6 0.7 0.8 0.9 1.0

(22)

Management practices affect attainable yields

Soil organic matter (%)

S

eed

-cot

ton

y

iel

d

(kg ha

-1

)

(23)

0 500 1000 1500 2000 2500 3000 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Yield without fertiliser Attainable yield (full fertiliser)

0 500 1000 1500 2000 2500 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Fertiliser use efficiency Yield gap

Response parameters, efficiency, yield gaps and soil organic matter

Soil organic matter (%)

S

eed

-cot

ton

y

iel

d

(kg ha

-1

)

(24)

Discontinuous fertiliser use

r2 = 0.7 r2 = 0.6 500 750 1 000 1 250 1 500 1 750 2 000 120 140 160 180 200 Period 1986-1996 Period 1997-2005

Fertiliser use, soil responsiveness and yield gaps in cotton-based cropping systems of N Cameroon