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Soil carbon
Diane Allen, DSITI: Carbon workshop Charleville 15/12/2015
Productivity benefits, methods explained, applicability in South West Queensland and implications
Soil and the carbon cycle
Soil carbon and productivity benefits
Measuring and modelling soil carbon
Soil carbon and the ERF – applicability and implications for south west Qld
Where do I find more info? Who can help?
Raymond (2005) Nature 436, 469-470
Kaiser et al. 2015, Nature comms
As some of the soil microbial community produce enzymes to break down organic
matter, C and N is lost in the process
Soil organic carbon – a part of soil organic matter
Organic matter makes up less than 10% of the soils mass but has a critical role in the physical, chemical and biological function of soils.
About 58% of the mass of organic matter exists as carbon. The content of carbon can be measured to estimate soil organic matter.
Source: WA Government
SOC: a function of the inputs and outputs
Courtesy Ram Dalal, DSITI
Plants & animals
Decomposableorganic residues
Soil biomass
Humus
Soil surface
CO2
CO2
CO2
Fresh residues
(labile) < 10%
Living organisms and roots
(labile) < 5%
Particulate organic C
(labile) 10 – 50%
Humus
(decadal) 33 – 50%
Char or black carbon/resistant
(inert) 1 – 30%
Adapted from Skjemstad & Baldock, 2000
Total carbon or a sum of its parts
Soil health
Nutrient cycling
Carbon sequestration
Tota
l C
arb
on
Hum
us,
part
icula
te, re
sis
tant
carb
on “
pools
”
What are the productivity benefits of managing SOC?
Sources: Text (United Nations Environment Program); Photos (Soil Science Society Australia)
Productivity benefits of soil organic carbon
Improving awareness of soil physical, biological and chemical conditions to maximise pasture production & business capacity to respond to change in weather, climate
Source: UNEP Year Book 2012
Productivity benefits of soil organic carbon
Physical – minimising sodic and erosive soil loss, soil sealing, salinity; maximising infiltration rates, water holding capacity, PAWC
Biological and chemical - enhancing native and sown pasture production; nutrient availability, supply and turnover
Response and Resilience – climate, weather and management interaction
Australia has 14 soil types (Soil Orders), reflecting the arid, strongly-weathered nature of the Australian continent
western Qld:Cracking clay soils – VertosolsMassive earths – KandosolsTexture contrast soils – SodosolsDeep sandy soils - Tenosols
Charleville
0 1 0 1 0 1 2 3 0 2 4 6
Soil 1 Soil 2 Soil 4Soil 3
0
50
100
150
200
So
il D
ep
th (
cm
)
Soil organic carbon content (% by weight)
2
What affects soil organic carbon levels?
Climate: Temperature, rainfall, Vapour Pressure DeficitVegetation typeSoil texture and type of clay and oxides (Parent Material)TopographyTimeThe above 5 factors govern the (natural) soil formation
Management: Land use practices and change Interaction of management and time
Images: Teresa Eyre and Queensland Government
Time
Equilibrium level
(Pasture/Forestry)
(cropping)
SO
C % Land use or
management change
New equilibrium level
Cropping and soil carbon, Queensland
Dalal and Meyer Aust. J. Soil. R, 1986
Sanderman and Baldock, S.R.Letters, 2010
Reducing SOC loss - Building SOC
Crop management• Soil fertility enhancement, better rotation, irrigation, fallow elimination
Conservation tillage• Stubble retention, reduced tillage, no-tillage
Pasture management • Fertilizer management, grazing management, earthworm introduction,
irrigation, improved grass species, legume introduction, sown pasture
Organic amendments• Animal manure, biosolids
Land conversion• Degraded cropland to pasture, bioenergy crop, agroforestry, biochar, land
clearing methods
Australian Government workstream: Soil Carbon
• Developing consistent methodology for quantification of soil carbon stocks
• Soil type x land management across climate gradient – cropping and grazing land management
• Special Edition of International Journal Soil Research 2013, 7-8, 561-780.
Soil Carbon Research Program (SCaRP) 2009-2012 (Program leader Jeff Baldock, CSIRO)
National Soil Carbon Program (NSCP) 2012-2017 (Program leader Ram Dalal, DSITI)
• Part of DAFF ‘Filling the Research Gap’ program
• Research outcomes underpin development of new abatement methodologies that land managers can use to participate in the Carbon Farming Initiative (CFI).
• Round 1: 15 soil projects, 11 Project Delivery Organisations
• Linkage with DAFF ‘Action on the Ground’ program which trial and demonstrate a range of on-farm technologies and practices
Sampling design and approach: Australia example
Challenge for getting reliable estimates of vegetation and soil carbon -representative sampling of the landscape
Do different scales of sampling require different sampling approaches?
Which sampling designs assess SOC (i) across the paddock, (ii) over different time scales, (iii) both?
Fresh residues
(labile) < 10%
Living organisms and roots
(labile) < 5%
Particulate organic C
(labile) 10 – 50%
Humus
(decadal) 33 – 50%
Char or black carbon/resistant
(inert) 1 – 30%
Adapted from Skjemstad & Baldock, 2000
Total carbon or a sum of its parts
Soil health
Nutrient cycling
Carbon sequestration
Tota
l C
arb
on
Hum
us,
part
icula
te, re
sis
tant
carb
on “
pools
”
Total SOC and C fractions – sieving & combustion
Total SOC: sample usually air-dried and sieved to 2mm particle sizePOC and HOC fractions: undertaken by wet-sieving, sorting organic matter on the basis of mesh size. POC (2mm - 53µm), HOC (<53µm). Sample then dried for analysis of carbon content
Prediction using infra-red spectroscopy
Baldock et al 2013 Soil Research
Relies on statistical relationships between infra-red (IR) soil spectra and results from soil C measurements
Grazing lands management, northern Australia and SOC
130 E 135 E 140 E 145 E 150 E
25
S20
S15
S10
S
Longitude
Latitu
de
1
2
3
4
5
6
7
Kidman Springs
8
9
10
11
12
13
14
15*
Toorak
16*
Wambiana
17
BRISBANE
DARWIN
1. Quantify the effect of rainfall, soil type, pasture systems and pasture management on soil organic carbon (SOC) stocks in grazing lands;
2. Estimate the soil carbon pools of total carbon stocks in grazing lands
3. Provide datasets for carbon models to account for pasture management practices under variable rainfall and soil type conditions.
Allen et al. 2013, Soil Research
130 E 135 E 140 E 145 E 150 E
25
S20
S15
S10
S
Longitude
Latitu
de
1
2
3
4
5
6
7
Kidman Springs
8
9
10
11
12
13
14
15*
Toorak
16*
Wambiana
17
BRISBANE
DARWIN
• 26 year trial, different pasture grazing• Soil C stock (0-0.5 m)
largest under 20% pasture utilisation and smallest under 80% pasture utilisation.
• Variability increased with depth.• soil C stocks correlated with an annual
measure of total standing dry matter (correlated with NDVI).
Pasture grazing - Sheep
Pringle el et al. 2013, Geoderma
130 E 135 E 140 E 145 E 150 E
25
S20
S15
S10
S
Longitude
Latitu
de
1
2
3
4
5
6
7
Kidman Springs
8
9
10
11
12
13
14
15*
Toorak
16*
Wambiana
17
BRISBANE
DARWIN
• Trial commenced in 1997 comparing different types of cattle grazing intensity (no grazing, light – moderate, heavy)
• 10 sites ~ 1,000,000m2 each• Soil C stocks showed a strong
interaction between grazing pressure x soil type
Grazing: stocking intensity – Beef cattle
Allen et al 2009; Pringle el et al. 2011
Full Carbon Accounting Model (FullCAM)
Understanding carbon changes using carbon models
Soil sub model
Years
Soil
org
anic
car
bo
n
(g C
kg-1
soil)
0 10 20 30 40 50 60 70
TOC
Land use change
Initiate land use
0
5
10
15
20
25
30
3315 43
HumC
ROCPOC
18 y 10 y
less humus C
more POC
Courtesy Jeff Baldock, CSIRO
Understanding carbon changes over time using carbon models
NSCP projects that have application for FullCAM
Soil carbon increase through rangeland restoration by facilitating native forest regrowth
Environmental plantings for soil carbon sequestration on farms
Native perennial vegetation: building stable soil carbon and farm resilience
Soil carbon benefits through reforestation in sub-tropical and tropical
Quantifying temporal variability of soil carbon
Understanding the influence of grazing pressure changes on soil organic carbon in the semi-arid rangelands of western NSW
The fate of aboveground carbon inputs: a key process that is poorly understood
Soil Methods Under ERF agriculture and vegetation sectors^
^as at 01/12/2015
Agriculture
•Beef cattle herd management •Destruction of methane from piggeries using engineered biodigesters *•Destruction of methane generated from dairy manure in covered anaerobic ponds *•Destruction of methane generated from manure in piggeries 1.1 *•Estimating sequestration of carbon in soil using default values•Fertiliser use efficiency in irrigated cotton•Reducing greenhouse gas emissions in beef cattle through feeding nitrate containing supplements *•Reducing greenhouse gas emissions in milking cows through feeding dietary additives *•Sequestering carbon in soils in grazing systems *
*methods transitioned from CFI to ERF on 01/07/2015
Vegetationmanagement
•Avoided clearing of native regrowth•Avoided Deforestation 1.1•Designated Verified Carbon Standard projects•Human-induced regeneration of a permanent even-aged native forest 1.1 *•Measurement based methods for new farm forestry plantations *•Native forest from managed regrowth *•Reforestation and Afforestation 2.0•Reforestation by Environmental or Mallee Plantings - FullCAM *•Savanna fire management
Defines the carbon estimation area (CEAs) and eligible project activities:• Increasing biomass yields (sustainable intensification) on crop or pasture areas by
optimising fertiliser, applying lime, introducing irrigation, or pasture renovation .• Converting land under crops to pasture (conversion to pasture).• Retaining crop residue in field rather than burning or baling it (stubble retention).
Provides CFI mapping tool and nominated permanence of 25 or 100y
Monitoring of soil and emission sources required - CEAs must also be monitored every six months to ensure that vegetation ground cover is maintained.
Specifies requirements for undertaking projects, reporting and auditing
Source: Commonwealth of Australia, 2015
Sequestering Carbon in Soils in Grazing Systems Determination (transitioned from CFI to ERF) - direct measurement method
• Activities : crop to permanent pasture, rejuvenating pasture, changing grazing • Resources provided re how and when to sample, where to analyse
Variable landscapes Sampling design Sampling in the field
Soil carbon in northern grazing lands: reflections from NSCP
• From 100y to 25y timeframes
• teasing apart climate and management; soil C management within whole GHG balance; financial forecasting at individual and aggregated scales; – streamlining determination eligibility
• If moving towards FullCAM approach, what are ‘missing gaps’ in rangelands for SOC? Including: biomass inputs, litter decomposition and turnover rates, SOC in relation to land type, quantifying grazing intensity and duration (BoS Management classes)
• Benefit of research: spatially-referenced data , link to existing and long-term data, ongoing monitoring
https://data.qld.gov.au/maps-geospatial/qld-globe
Site observationSoil morphology describedLab test results e.g. pH, electrical conductivityChloride, organic Carbon, Total N, K, P
international-year-of-soil-2015-activities
http://www.fao.org/soils-2015/
http://www.soilscienceaustralia.com.au/
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