Firstly, results on the influence of conventional crop management systems (based on inorganic fertilizers) and organic cropping systems (based on organic fertilizers) on soil properties, crop production and greenhouse gas emissions are presented. These results were generated through laboratory assays, field measurements and process-based biogeochemical models (the past). Secondly, current efforts on improving processes in the greenhouse gas laboratory (Soils Research area), to ensure the generation of quality results are explained (the present). Thirdly, a vision on the roadmap for climate change mitigation research and potential contributions to CIAT’s strategic initiatives and goals is presented (the future).

1. TOWARDS SMARTER AGRICULTURAL
SYSTEMS: PAST, PRESENT AND
ENVISAGED FUTURE SOILS
RESEARCH
Ngonidzashe Chirinda
Soils Research Area (Scientist- Soils and Climate Change)
1

2. Presentation Agenda
• Past: Laboratory methodologies, soil properties,
crop production, GHG emissions, Life cycle
assessments and modelling
• Present: Laboratory and field processes and
capacity building
• Future: Advanced analytical infrastructure, low
emission farms, regional networks and
partnerships
2

3. The Past
• Post-cold-storage conditioning time affects soil
denitrifying enzyme activity
• Soil properties and crop production
• Soil GHG emissions
• Modelling
• Life cycle assessment: C-footprint of cropping systems
3

4. Post-cold storage conditioning time
affects soil denitrifying enzyme activity
DEA assay basis: soil enzyme
concentration directly
proportional to denitrification
rates when no other factors
are limiting
-
nitrate reductase
2NO3
-
nitrite reductase
2NO2
2NO
nitric oxide reductase
N2O
nitrous oxide reductase
N2
4

5. Hypothesis: Conditioning time (post-cold storage warming-up
time prior to soil analysis) significantly influences results
obtained through the denitrifier enzyme activity (DEA) assay.
5

6. Findings
• Fluctuation of DEA post-cold-
storage
• Standardization of
procedures – overnight
warming
Chirinda et al. 2011: Commun. Soil Sci. Plant Analy. 6

7. Organic fertilizer Inorganic fertilizer
CO2
Microbial
biomass
+
NH4
-
NO3
-
Soil organic matter
N2
N2O
NO2
Mineralization
-
NO2
Nitrification
Denitrification
NO
Immobilization
•C availability
•Anaerobicity
•Residence time
•NO3
- availability
7

8. Conventional C4/+IF/-CC
spring barley faba bean potato winter wheat
Organic O4/+M/-CC
spring barley faba bean potato winter wheat
Organic O4/-M/+CC
spring barleyCC faba beanCC potato winter wheatCC
Organic O4/+M/+CC
spring barleyCC faba beanCC potato winter wheatCC
Organic O2/+M/+CC
spring barleyCC ley potato winter wheatCC
Catch crops: Ryegrass, chicory, red and white clover
Ley: Ryegrass, red and white clover
8

9. Hypothesis
Increased C inputs via crop residues,
catch crops and manure would have
positive and additive effects on soil C
storage and microbial activity leading to
improved N availability and crop
productivity.
9

10. Pearson correlation coefficients (r) between different variables in soils
under winter wheat
C input SOC Resp. MBN PMN PAO DEA N2O Dp/Do
C input
SOC
Resp. 0.95***
MBN 0.65* 0.70*
PMN 0.71* 0.75* 0.90**
PAO 0.85** 0.74* 0.61†
DEA 0.74* 0.64*
N2O −0.59† −0.60† −0.60†
Dp/Do
BD −0.73* 0.73* −0.55†
†,*, **,*** P<0.10, P<0.05, P<0.01, P<0.001, respectively.
10
Chirinda et al. 2010a: Agric. Ecosystem Environ.

11. Grain (t ha-1) and Nitrogen (kg N ha-1) yields at harvest
System Grain N Grain N
___winter wheat___ _____spring barley___
Fertilizer type effect
C4/+IF/−CC 9.5a 164a 5.5a 104a
O4/+M/−CC 5.0b 71b 3.3b 53b
O4/−M/+CC 2.8c 39c 4.5c 74c
O4/+M/+CC 6.3b 98b 5.2a 91a
O2/+M/+CC 5.8b 87b 5.7a 99a
Manure effect
Chirinda et al. 2010a: Agric. Ecosyst. Environ. 11

12. Conclusions
• The hypothesis that increased C (and N) inputs
increase microbial activity, N availability and crop
productivity is accepted
• There was no evidence for additive effects on soil
C storage
12

13. Greenhouse gas emissions
Agriculture roles to climate change
Victim: productivity influenced by temp. rise
Source: contributes to release of three greenhouse
gases CO2, CH4 and N2O
Solution: significant amounts of CO2 can be
absorbed through photosynthesis
13

14. Hypothesis
Restricted availability of N in organically
managed systems leads to lower N2O emissions
compared to the inorganic fertilizer-based
systems receiving higher N inputs.
14

15. Winter wheat yields, cumulative and relative soil N2O emissions
Cum. N2O
emission
Grain yield Emissions per yield Emissions per N
applied
Site/system mg N m-2 kg DM m-2 mg N2O-N kg-1 DM kg N2O-N 100 kg-1 N
Flakkebjerg
C4/+IF/-CC 137a 0.76a 184a 0.81a
O4/+M/-CC 71a 0.28b 274a 0.70a
O4/+M/+CC 54a 0.38b 133a 0.53a
O2/+M/+CC 80a 0.39c 205a 0.80a
Foulum
Fertilizer type effect
C4/+IF/-CC 92a 0.95a 96a 0.56a
O4/+M/-CC 68a 0.50b 134a 0.63b
O4/+M/+CC 81a 0.63c 130a 0.75b
O2/+M/+CC 63a 0.58bc 108a 0.62b
Chirinda et al. 2010b: Agric. Ecosyst Environ. 15

16. 0 20 40 60 80
% WFPS
80
N2O flux (μg N m-2 h-1)
60
40
20
0
<10 kg NO3-N ha-1
>10 kg NO3-N ha-1
Regulation of soil N2O
emissions at Foulum
WFPS
Temperature
Interactions between soil NO3
- &
• soil C
• WFPS
• temperature
log(N2O) = 1.86 – 0.0029 W – 0.0081T – 0.152 C  log(N) + 0.0096 W  log(N) + 0.069 T  log(N)
Chirinda et al. 2010b: Agric. Ecosyst. Environ. 16

17. Conclusions
• Restricted availability of N did not significantly reduce N2O
emissions from low-input organically managed systems:
hypothesis is rejected
• In the organic systems, high N2O emissions per N applied
and low yields are challenges that need to be addressed
• Avoid high soil mineral N concentrations
17

18. Hypothesis
At their current stage of development, both
MoBiLE-DNDC and FASSET are capable of
adequately simulating soil N2O emissions from
arable cropping systems fertilized using either
organic or inorganic sources of N
18

19. Models
MoBiLE (Modular Biosphere Simulation Environment):
• Framework enables flexible integration of different sub-models
- Sub-models the MoBiLE-DNDC used:
- soil physics, water cycling & biochemistry (PnET-N-DNDC)
- crop growth & management (agriculture-DNDC 9.2)
• Eight soil organic matter pools
• N2O produced through “anaerobic balloon“ concept
Farm Assessment Tool (FASSET):
• Soil-plant-atmosphere sub-models
• Seven soil organic matter pools
• N2O produced through “Hole-in-the-Pipe“ concept
19

20. ”Anaerobic balloon” concept
• Eh 350 to 250 mV
N2O
Anaerobic
microsites
NO3 NO2 NO N2O N2
NO3 NO2 NH4
Aerobic
microsites
NO
20

21. ”Hole-in-the-Pipe” concept
N2:N2O N2:N2O
• N2O production: nitrification and denitrification by applying semi-empirical
functions regulated by environmental factors
• Potential N2O emission divided into N2 and N2O emission using semi-empirical
relations as controlled by soil physical properties and depth
• Proportions N2O emitted remain constant at specific moisture content
21

22. Soil N2O
emissions
Daily flux Cumulative flux
4
3
2
1
0
4
3
2
1
0
4
3
2
1
0
-1
120
100
80
60
40
20
0
120
100
80
60
40
20
0
120
100
80
60
40
20
0
120
100
80
60
40
20
0
Oct-07 Feb-08 Jun-08
-1
-1
4
3
2
1
0
-1
Oct-07 Feb-08 Jun-08
MoBiLE-DNDC
FASSET
Measured
C4/+IF/-CC
O4/+M/-CC
O4/+M/+CC
O2/+M/+CC
N2O fluxes (g N ha-1 d-1)
Cum. N2O emissions (kg N ha-1)
Oct 08 Oct 08
Chirinda et al. 2010: Plant and Soil 22

23. Findings
• Both models simulated N2O emissions from the
inorganic fertilizer-based system fairly well
• FASSET overestimated N2O emissions in organic
systems, especially systems that included catch crops
23

24. Carbon footprint using a Life Cycle
Approach
Knudesen et al 2014: Journal of Cleaner production 24

25. • C-footprints per kg Findings
DM conventional =
organic rotation
• Including legumes -
fermenting them in
biogas plants & spread
them for plant
nutrition -
significantly lowers C -
footprint per kg cash
crop DM
Contributions to C-footprint per unit per kg cash crop DM
at farm gate
25

26. The Present
• Laboratory processes
• Proposals
• Capacity building
26

27. Laboratory processes
• Duration of sample
storage
• Diurnal variation of
GHG emissions
• Sampling chambers: for
rainfed crops and also
for flooded rice systems
0 20 40 60 80 100 120 140 160
Methane
0 20 40 60 80 100 120 140 160
Day
2500
2000
1500
1000
CH4 ppm
500
12
10
8
2
0
Carbon dioxide
Day
CO2 ppm
0
Nitrous oxide
0 20 40 60 80 100 120 140 160
Day
N2O ppm
2
1
0
Loaiza et al. (unpublished)
27

28. Capacity building
• Friday Science
• MSc Students – funded by SAMPLES,
CLIFF Network, Medellin University
• Global Research Alliance (CIAT
technical hub for paddy Rice Latin
America Sub-group);
28

29. Proposals
• Mitigation Options to Reduce Methane
Emissions in Paddy Rice- funded by CCAC
• LivestockPlus: Supporting low emissions
development planning in the Latin
American cattle sector -CCAFS (revised and
submitted)
• GreenRice (submitted)
• Vinnase and GHG emissions (requested)
• Enteric methane emissions (submitted)
29

30. The Future
• Improved temporal
resolution of
measurements
• Co-designing for eco-efficient
farms (smart
farms)
• Regional partnerships
and GHG networks
30

31. Take home message
Capacities I bring to the SOILS
team and CIAT table
• Methodology improvement
• Soil science
• Crop production
• Greenhouse gas emissions
• Modelling
• Life cycle assessments 31