Soil Organic Carbon: Challenges & Opportunities Assoc. Prof. Frances Hoyle UWA School of Agriculture and Environment Daniel Murphy, Yichao Rui, Rebecca O’Leary, Courtney Creamer, Emily Cooledge, Anna Ray, Davey Jones, Steve Rushton, Elizabeth Stockdale, Yoshi Sawada, Emilia Horn, Manjula Premaratne
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Soil Organic Carbon: Challenges & OpportunitiesAssoc. Prof. Frances Hoyle UWA School of Agriculture and Environment
Daniel Murphy, Yichao Rui, Rebecca O’Leary, Courtney Creamer, Emily Cooledge, Anna Ray, Davey Jones, Steve Rushton, Elizabeth Stockdale, Yoshi Sawada, Emilia Horn, Manjula Premaratne
Complexity of the soil matrix
• Soil properties, environment and management interact.• Large data sets enable new ways of looking at changes soil quality. • Focus is to predict how management of one property alters the others - then use these to run
scenarios to manage risk.
Pauline Mele
0%
20%
40%
60%
80%
100%
Tota
l Car
bon
Soil
N s
uppl
y
Dis
ease
pH (0
-10)
pH (1
0-20
)
pH (2
0-30
)
Elec
rical
Con
duct
ivity
Wat
er R
epel
lenc
y
Bulk
Den
sity
RedAmberGreen
Biology PhysicsChemistry
pH
Soil organic matter
Electrical Conduct.
CEC
Water repellence
Clay content
Compaction
Hardsetting
Available H2O
Erosion
Climate AgronomicManagement
Disease
Pathogenic Nematode
Labile organic matter
Microbial biomass
Biological N supply
Soil Qualitywww.soilquality.org.au
MED pH Soil strength (MPa)
Dept
h (c
m)
0 cm
10 cm
40 cm
50 cm
Net Primary ProductivityStored soil water + [Growing season rainfall – Evaporation]
x biomass/mm
Soil organic matter0.1 – 10%
Living 15%
Microorganisms75-90%
Mycorrhizae
Denitrifiers
N fixation
Decomposers
Microbial activity
Nutrient Cycling EnzymesAggregate
stabilisation
Diversity
e.g. bacteria and fungi
Resilience
Roots 5-15% Fauna 5-10%
What are the components of SOM?
Contaminantdegradation
= C (58%), O, H, S, N, P, K, Ca, Mg< 2 mm =
Soil organic carbon fractions & ‘permanence’
Particulate
Soluble & suspended
Humus & Resistant
Minerals
Soil organic carbon0.1 – 5.0 %
26%44%30%
1.5% C
0.8% C
0.3% C
Factors Driving Carbon Storage in Soil
Satellite image of the WA agricultural area – sampling sites (>1300)
Adapted from Ingram & Fernandez 2001
Presenter
Presentation Notes
Science: Theoretically 50% or more of global GGE can be offset annually over the next 30+ years by ‘regrowing’ soil carbon (C) Unarguably the functional role of C vital to production and environmental goals
Influence of clay content on SOC in a 10-hectare area under cereal-legume rotation
SOC
(%; 0
-10
cm)
Clay Content (%)Hoyle, Baldock & Murphy (2011) Book Chapter
P Poulton, Rothamsted Research, UK.
Building SOC
• A natural equilibrium exists for the retention and loss of organic matter, with significant seasonal variability
• In low cation sandy soil a lower proportion of organic inputs are protected and retained• Maintaining soil organic carbon requires continued inputs
P Grace, Australia (2006).
Silty clay loam Soil with less clay
% in
put r
etai
ned
CEC (meq/100 g)0.5
1.0
2.0
3.0
Soil
orga
nic
carb
on (%
)
Presenter
Presentation Notes
After slide put back in grace figure
WA SCaRP Carbon & FRG projects
• +1300 sites across South West WA• Seven different sample areas:
• Esperance (beef pastures).• Young River (cropping and pastures).• Kalgan (cropping and pastures).• Kojonup (cropping and pastures).• Avon (cropping).• Geographe (beef and dairy pastures).• Mingenew (cropping).
• Target specific soil types (deep sand, sandy duplexes, gravelly duplexes, red loams) and land-uses.
• Measured soil variables inc. carbon & fractions
“Under current management strategies is there any room for movement in carbon storage?”
Annual rainfall- SOC (t C/ha) linked to annual rainfall
(mm)- Rainfall drives net primary productivity- Larger range of data in medium-high
rainfall driven by management and soil properties
- SOC differences between pasture and cropping often correlated with climate (‘fit for purpose’)
- Drying climates??? Hoyle et al. 2016 Sci. Rep. Annual average rainfall (mm)
300 400 500 600 700 800 900So
il or
gani
c ca
rbon
(t C
/ha,
0-
30cm
)0
5010
015
020
0Meta-analysis results
Soil
Org
anic
Car
bon
(t/ha
, 0-3
0 cm
)
Annual Rainfall (mm; 30y average)
WA SCaRP Carbon & FRG projects
30y average5y average
TemperatureChange point regression analysis
- When average daily temperature is >17°C, there is a significant decrease in SOC
- Represents critical limit for SOC storage potential for different climatic regions in WA????
- Linked to net primary productivity and decomposition rates
Aim: Determine retention of organic matter in a low rainfall cropping system.
Paper in preparation
Buntine organic inputs trial(established 1993)
Main Treatments:
No Till (Control)
Burnt
Till
Till+organic matter (5 x 20 t OM/ha)
FIELD TRIALBuntine (2016) – 13 years on
• In 2016 having added 100 t/ha organic matter (48 t C/ha), SOC stocks increased by 7 - 8 t C/ha• 61% SOC in surface 10 cm (66% in min till)• Stubble retention vs. burning – no change, till vs. no till – no change*• ‘New’ OM loss equivalent to 1.1 t C/ha/year without new inputs
• Improve water use efficiency by plants (e.g. remove sub-soil constraints) to increase potential C inputs to soilo Measurable change often takes decades
• Increase proportion of year (or area) with actively growing plants where viable
• Utilise organic input streams where viable
Soil organic carbon is critical to maintaining function & resilience …….
FREE TO DOWNLOADFROM iBooks
JUST SEARCH‘SOIL QUALITY’
Hoyle F.C., Baldock J.A. and Murphy D.V. (2011). Soil organic carbon – Role in rainfed farming systems with particular reference to Australian conditions. In: Rainfed Farming Systems (P. Tow, I. Cooper, I. Partridge and C. Birch; Eds.). Springer International.