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

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

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

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

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

”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

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

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

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

• 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

The Present
• Laboratory processes
• Proposals
• Capacity building
26

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

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

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

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

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