The document summarizes challenges and opportunities for sustainable intensification in drylands through symbiotic nitrogen fixation (SNF) in pulses. It discusses how SNF can help address issues like excess nitrogen in the environment, slow productivity growth of pulses, and lack of alternatives to unsustainable fertilizer use. While SNF is sensitive to stresses like drought, opportunities exist to improve yields through breeding, agronomy, and integrated soil management. Research on SNF physiology and genetics, as well as holistic approaches involving farmers, could help realize untapped potential for increasing pulses' role in cropping systems under climate change.

1. A Plus for Pulses: Symbiotic Nitrogen
Fixation for Sustainable Intensification in
the Drylands Rachid Serraj
Outline
• Pulses & SNF challenges in a nutshell
• N2 fixation, Abiotic stress & Climate Change
• SNF for sustainable intensification
• Take home messages
International Conference on Pulses – Marrakech, April 2016

2. “ Chemical fertilizer is the fuel that
powered the Green Revolution's
”
Norman Borlaug
Is this sustainable/generalizable?
What are the alternatives?
Africa accounts for <1% of global fertiliser market and cost of fertiliser can
vary significantly between and within countries.
e.g., a farmer will pay ~ $330 per t of fertiliser in Kenya vs. $830 in Angola
[Montpellier Panel Report, 2013]

3. Excess N in the environment

4. FAOSTAT Database, Oct. 2014
Evolution of Global Cereal & Legume Production
(pulses + groundnut + soybean)

5. Annual global pulse production, harvested area and yield
in 2008–10 & annual rate of change from 1991 to 2010
Fischer, Byerlee & Edmeades (2014) Crop yields and global food security, ACIAR

6. Slow
Productivity
growth
Yield gap
Price relative
to other
commodities
Shift in diet
Income
growth
Demand
static
Low profitability &
competitiveness
No technological
breakthroughs
Pulses pushed
into marginal
lands
(Kelley & Paratharasathy, Chickpea competitivenes in India, (1994)

7. March 2016: price of pulses skyrocketing…
« Ce projet inédit vise à faire du pays un hub
pour exporter les trois-quarts de sa production
en Europe et en Afrique.. »

8. Slow
Productivity
growth
Yield gap
Price relative
to other
commodities
Shift in diet
Income
growth
Demand
static
Low profitability &
competitiveness
No technological
breakthroughs
Pulses pushed
into marginal
lands
Policy (LCA):
subsidies,
Research
Protein production
& health;
Sustainability
effects on soil &
people
(Kelley & Paratharasathy, Chickpea competitivenes in India, (1994)

9. Life cycle and economic assessment of Western Canadian pulse
systems: The inclusion of pulses in crop rotations

10. Factors underlying legume yield gaps
e.g. reasons for the decline in grain legumes in North Africa include:
 non-availability of improved seed,
 lack of suitable varieties for mechanical harvesting,
 low prices,
 high production costs,
 orobanche infestation + other pests & diseases
 climatic stress, especially severe droughts,
 losses of human capacity to conduct R4D.
Morocco and Tunisia were formerly exporters of food legumes but
have now become importers!
From CRP on Grain Legumes
 Only 25% of legume crop area in the developing world is high
input/irrigated, compared to 60% of the cereal area.
 Only 6% of fertilizer in SS Africa is used on grain legumes,
compared to 26% for maize.
CGIAR SPIA - From Akibode & Maredia (2011)

11. Examples:
• Drought
• Nitrate
• Low P
• Salinity
• Temperature
• Climate change?
SNF Agronomic
constraints:
Serraj & Adu-Gyamfi, 2004
 How much progress are-we
making in the search for
molecular / physiological
mechanisms? (late 70ies,
90ies, 2000,….)

12. Strategy:
Physiological dissection & screening
Breeding & Genetics
Agronomy, on-farm testing & adoption
SNF Response to Drought
SNF extremely sensitive to stress:
 Nitrogenase more sensitive than PS, NRA..
Limitation of legume yield, protein production..

13. Relationship between Leaf and
Nodule Metabolism
O2N2
ATP
ADP
Ureides
Amino acids
Ureides
Amino acids
NH4
+
N2
H2O
H2O
CO2
hn
Sucrose
Feed Back
Inhibition
Serraj et al. (1999). Plant Physiol .119: 289-296

14. Species No. Of
Observations
Fraction with
RDN: RTR > 1.0
Sap Ureide
(mM)
Soybean cv. Biloxi 51 0.10 458
Cowpeacv. CB9 21 0.14 216
Black gram cv. Regur 10 0.30 ^
Common Bean cv. Roma 29 0.86 45
Pea cv. Sugar snap 41 0.95 15
Lupine cv. Ultra 44 0.77 0
Peanut cv. Florunner 80 0.94 ‡
Faba beancv. F223 23 0.96 0
Chickpea cv . Sombrero 37 0.97 0
Sinclair & Serraj (1995). Nature 378: 344
Species Comparison of sensitivity of N2 fixation to drought

15. Combined CO2 and Drought effects on growth
parameters, BNF & WUE
USDA-Univ. Florida, Gainesville

16. Response of Plant Growth, PSR, Transpiration and
N2 Fixation to FTSW under ambient & Elevated CO2
Exp. 2
FTSW
0.00.20.40.60.81.0
NormalizedARA
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Exp. 1
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
y = 1/[1 + 7.1 exp(-13.8 x)], r
2
= 0.75
y = 1/[1 + 1.7 exp(-18.7 x)], r
2
= 0.39
y = 1/[1 + 4.7 exp(-8.3 x)], r
2
= 0.73
y = 1/[1 + 0.8 exp(-6.5 x)], r
2
= 0.27
360 mmol mol
-1
700 mmol mol
-1
Exp. 2
FTSW
0.00.20.40.60.81.0
NormalizedARA
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6 Exp. 2
FTSW
0.00.20.40.60.81.0
NormalizedARA
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Exp. 1
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
y = 1/[1 + 7.1 exp(-13.8 x)], r
2
= 0.75
y = 1/[1 + 1.7 exp(-18.7 x)], r
2
= 0.39
y = 1/[1 + 4.7 exp(-8.3 x)], r
2
= 0.73
y = 1/[1 + 0.8 exp(-6.5 x)], r
2
= 0.27
360 m
Exp. 1
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
y = 1/[1 + 7.1 exp(-13.8 x)], r
2
= 0.75
y = 1/[1 + 1.7 exp(-18.7 x)], r
2
= 0.39
y = 1/[1 + 4.7 exp(-8.3 x)], r
2
= 0.73
y = 1/[1 + 0.8 exp(-6.5 x)], r
2
= 0.27
360 mmol mol
-1
700 mmol mol
-1
Serraj et al., PCE, 1998
Serraj et al. Global Change Biol., 1999

17. Dynamics of Ecosystem Biodiversity under
Climate Change: N-Fixers vs. non-N-Fixers
Will N2-fixing plants benefit more from atmospheric CO2
enrichment than non-N-fixers, leading to a competitive
advantage, thereby changing the dynamics of ecosystems
biodiversity?
Little evidence to suggest that N-fixing legumes will out-
compete non-N-fixing plants in ecosystems.
worth revisiting in drylands?
Few studies of species competition in mixed ecosystems:
Arnone, Functional Ecology (1999); Matthis & Egli, Oecologia (1999); Stocklin &
Korner, Functional Ecology (1999); Navas et al, New Phytologist (1999),..

18. The Brazilian success story:
Area planted, total production, productivity &
total N exported on soybean grains in Brazil.
Year Area planted
(ha)
Grain Prod
(ton)
Productivity
(kg/ha)
N exported4
(1000 t)
1970-711
1,716,420 2,014,291 1,174 121
20003
12,773,272 31,195,344 2,442 1,946
1
IBGE (1992); 2
IBGE (October 97, July 98), FIPE AGRÍCOLA (1997, 1998);
3
Agrianual, (1999,2000); 4
N Considering 6% N on grain.
Price of N-fertiliser in Brazil ~$0.79 per kg >> ~ $1.5 Billion py??
Franco et al., 2002

19. C:N Ratio in different soils under No-till,
conventional tillage and forest
Sisti, Santos, Urquiaga, Alves, Boddey, 2001
NitrogênioTotal(g.kg-1)
0 1 2 3 4
Carbonoorgânicototal(g.kg-1)
5
10
15
20
25
30
35
40
45
R2=0,94
Y=0,5+12,37.X
(n=420)
p<0,001
Nitrogen (g.kg-1)
Carbon x N in the Soil:
To accumulate 1 Mg of C as
SOM it is necessary to also
incorporate about 80 kg of N.
overall N balance of crop
rotation/cropping system will
have a major influence on
long-term C accumulation or C
loss.

20. A Holistic approach:
• Legume-Rhizobium Biodiversity & Genomics
• Integrated Soil Fertility Management
• Breeding-Physiology – Agronomy
• Participatory Research, Systems & Modeling
• Socioeconomics, Political Economy
From Genes to Farmers’ Fields
CPBNF Vision
CPBNF Workshop -Montpellier, June 2002

21. A successful model for SSA and
WANA?
Full adoption of the N2Africa package increases yield, but to close the
yield gap between current average and attainable yield and to achieve
the yield increases stated in the Vision of Success more than the use of
N2Africa technologies alone is needed.

22.  Untapped potentials: promising crops, traits and
opportunities (niches, germplasm & genetic variation)
 Legumes & SNF in the heart of “CSA” practices: Prospects
for increased role of legumes/NF in cropping systems under CC
 Future thrusts of agroecological approaches in the
drylands – Need to broaden the scope of R&D. SNF research
should proceed along the process-component-systems continuum,
demand-driven and on-farm problem solving
Take home messages
Thank you!